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use of methyl bromide and the economic impact of its proposed ban on the Florida fresh fruit and vegetable industry

HIDE
 Front Cover
 Title Page
 Table of Contents
 Abstract
 Acknowledgement
 Executive summary
 Introduction
 The evolution and use of methyl...
 Chemical and non-chemical alternatives...
 Commodity production and pest control...
 The economic impact of a methyl...
 Summary and conclusions
 Reference
 List of common methyl bromide...
 Commercial application of methyl...
 Alternatives to methyl bromide...
 The market for Florida fruit and...
 A mathematical model of the North...
 A mathematical model of the world...
 Next best alternatives to methyl...
 Back Cover
 
Permanent Link: http://ufdc.ufl.edu/UF00027612/00001

Material Information

Title: use of methyl bromide and the economic impact of its proposed ban on the Florida fresh fruit and vegetable industry
Series Title: Bulletin (tech.) - University of Florida Agricultural Experiment Station ; 898
Physical Description: Book
Language: English
Creator: Spreen, T. H. (Thomas H.)
VanSickle, J. J. (John J.)
Moseley, A. E. (Anne)
Deepak, M. S.
Mathers, L. (Lorne)
Publisher: University of Florida, Agricultural Experiment Station, Institute of Food and Agricultural Sciences,
Publication Date: 1996

Record Information

Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
System ID: UF00027612:00001

Permanent Link: http://ufdc.ufl.edu/UF00027612/00001

Material Information

Title: use of methyl bromide and the economic impact of its proposed ban on the Florida fresh fruit and vegetable industry
Series Title: Bulletin (tech.) - University of Florida Agricultural Experiment Station ; 898
Physical Description: Book
Language: English
Creator: Spreen, T. H. (Thomas H.)
VanSickle, J. J. (John J.)
Moseley, A. E. (Anne)
Deepak, M. S.
Mathers, L. (Lorne)
Publisher: University of Florida, Agricultural Experiment Station, Institute of Food and Agricultural Sciences,
Publication Date: 1996

Record Information

Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
System ID: UF00027612:00001

Table of Contents
    Front Cover
        Front Cover
    Title Page
        Title Page
    Table of Contents
        Page i
        Page ii
        Page iii
        Page iv
    Abstract
        Page v
    Acknowledgement
        Page vi
    Executive summary
        Page vii
        Page viii
        Page ix
        Page x
    Introduction
        Page 1
        Page 2
        Page 3
        Page 4
    The evolution and use of methyl bromide in the vegetable and citrus industries
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
    Chemical and non-chemical alternatives to methyl bromide use
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
    Commodity production and pest control practices
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
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        Page 47
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        Page 50
        Page 51
        Page 52
        Page 53
        Page 54
        Page 55
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        Page 62
        Page 63
        Page 64
        Page 65
        Page 66
        Page 67
        Page 68
        Page 69
        Page 70
        Page 71
        Page 72
        Page 73
        Page 74
        Page 75
        Page 76
        Page 77
        Page 78
        Page 79
        Page 80
        Page 81
        Page 82
        Page 83
        Page 84
        Page 85
        Page 86
    The economic impact of a methyl bromide ban
        Page 87
        Page 88
        Page 89
        Page 90
        Page 91
        Page 92
        Page 93
        Page 94
        Page 95
        Page 96
        Page 97
        Page 98
        Page 99
        Page 100
        Page 101
        Page 102
        Page 103
        Page 104
        Page 105
        Page 106
        Page 107
        Page 108
    Summary and conclusions
        Page 109
        Page 110
        Page 111
        Page 112
        Page 113
    Reference
        Page 114
        Page 115
        Page 116
        Page 117
        Page 118
        Page 119
        Page 120
        Page 121
        Page 122
        Page 123
    List of common methyl bromide formulations
        Page 124
        Page 125
        Page 126
        Page 127
        Page 128
    Commercial application of methyl bromide
        Page 129
        Page 130
        Page 131
    Alternatives to methyl bromide and their use in Florida
        Page 132
        Page 133
        Page 134
        Page 135
        Page 136
        Page 137
        Page 138
        Page 139
        Page 140
        Page 141
        Page 142
        Page 143
        Page 144
        Page 145
        Page 146
    The market for Florida fruit and vegetables
        Page 147
        Page 148
        Page 149
        Page 150
        Page 151
        Page 152
        Page 153
        Page 154
        Page 155
        Page 156
    A mathematical model of the North American winter vegetable market
        Page 157
        Page 158
        Page 159
        Page 160
        Page 161
        Page 162
        Page 163
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        Page 190
        Page 191
        Page 192
        Page 193
        Page 194
        Page 195
        Page 196
    A mathematical model of the world market for Florida grapefruit
        Page 197
        Page 198
        Page 199
        Page 200
    Next best alternatives to methyl bromide for Florida fruit and vegetables
        Page 201
        Page 202
        Page 203
        Page 204
        Page 205
    Back Cover
        Back Cover
Full Text
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DOCUMENT


Bulletin 898 (Tech.)


r? .'
c-' Z9


Use of Methyl Bromide
and the
Economic Impact of Its Proposed Ban
on the
Florida Fresh Fruit and Vegetable Industry



T. H. Spreen
J. J. VanSickle


A. E. Moseley
M. S. Deepak
L. Mathers


i.rston Science
Library
AUG 12,1996

Universiy of Florida


S-, UNIVERSITY OF
. FLORIDA
Agricultural Experiment Station
Institute of Food and Agricultural Sciences


I -

I















THE USE OF METHYL BROMIDE AND THE ECONOMIC IMPACT OF ITS
PROPOSED BAN ON THE FLORIDA FRESH FRUIT AND VEGETABLE INDUSTRY




by


Thomas H. Spreen
John J. VanSickle
Anne Moseley
M.S. Deepak
Lore Mathers


Thomas H. Spreen and John J. VanSickle are Professors, Anne Mosely is Economic
Analyst, M.S. Deepak is Post Doctoral Research Associate, and Lore Mathers is Graduate
Research Assistant, Food and Resource Economics Department, University of Florida,
Gainesville, Florida.








ASSESSMENT OF THE LONG TERM ECONOMIC IMPACTS OF THE LOSS OF
METHYL BROMIDE ON FLORIDA

TABLE OF CONTENTS ............................... .......

ABSTRACT .......... ....................................

ACKNOWLEDGEMENTS ......................................

EXECUTIVE SUMMARY ......................................

SECTION 1. INTRODUCTION ...................................

Organization of this Report ..................................

SECTION 2. THE EVOLUTION AND USE OF METHYL BROMIDE IN THE
VEGETABLE AND CITRUS INDUSTRIES ..................

H historical Overview ......................................

Development and Use of the Chemical .....................
M ethyl Bromide in the Soil .............................
Methyl Bromide as a Potential Contributor to Ozone
D epletion . . . . . . . . .
Legal Development Surrounding Methyl Bromide ................
Methyl Bromide and Safety-Health Concerns ...................
Application of Methyl Bromide as a Soil Fumigant ...............

SECTION 3. CHEMICAL AND NON-CHEMICAL ALTERNATIVES TO
METHYL BROMIDE USE .............................

Chemical Alternatives to Methyl Bromide ..........................

Basamid Granular ...................................
V orlex . . . . . . . . . . .
Vapam ...........................................
Telone II and Telone C-17 ..............................
C holorpicrin . . . . . . . . . .

Non-Chemical Alternatives ..................................

Reduced Use of Methyl Bromide ................. ........
Constructed Barriers .................................
Crop Rotation ........... ................ .... ......


i







. . . . . . . . 29


Solarization ................... .................... 30
M microwave ........................................ 31
Soil Flooding ...................................... 31
Soil Amendments .................... ............. 31
Host Plant Resistance ................................. 32
Fallow Land ...................................... 33
Cover Crops ..................................... 33

SECTION 4. COMMODITY PRODUCTION AND PEST CONTROL PRACTICES 34

W atermelons ........................................... 34

Cultural Practices ................................... 34
D diseases ......................................... 36
Nematodes ........................................ 38
W eeds .......................................... 39
Insects .... ... ... .... ....... .... ... .. .... ..... 40
Trends .......................................... 40

Tom atoes ............................................. 40

Cultural Practices ................................... 41
Planting Techniques ................................. 44
Staking ............... ............................ 45
D diseases ............... ....................... 45
Nematodes .................................... ... 50
W eeds .................................. ..... 50
Insects .. .. .... ... .... ..... ..... .... ... ... .. .. 51

Strawberries ........................................... 51

Cultural Practices ................................... 52
D diseases ......................................... 54
Nematodes ..................................... 56
W eeds .......................................... 57
Insects .... ..... .... ........ .... .. ... .. .. .... .... 58

Peppers .............................................. 58

Cultural Practices .................................. 59
Diseases ................................... ....... 61
Nematodes ......... .............................. 63
W eeds .......................................... 63


Hot Water or Steam .






Insects . .

Eggplant ...........


Cultural Practices
Diseases . .
Nematodes ....
Weeds ... ..
Insects .......

Cucumbers .........

Cultural Practices
Diseases ......
Nematodes ....
Weeds .......
Insects .......


Squash ..............


Cultural Practices
Diseases ......
Nematodes ....
Weeds .......
Insects .......


...... 78
. . 80
......80
. .. 81
. ..... 81
...... 82


Fresh Citrus .............


SECTION 5. ECONOMIC IMPACT OF A METHYL BROMIDE BAN .......... 87

Objectives ............................................. 87

The Impact on Production of Vegetables from a Methyl Bromide Ban ........ 88

M ethodology ...................................... 88
Empirical Results ...................................90

The Impact of a Methyl Bromide Ban on the Florida Citrus Industry ........ 98

Solution of the Model ................................ 100
Oranges, Tangelos and Tangerines ........................ 102
Total Impact ...................................... 104

The Overall Economic Impact on the State of Florida ................. 105


iii


.64


.. 65
.... 67
... 69
.... 70
.... 71

.... 71

.... 72
.. 74
.... 76
. 76
....76
.... 77

.... 78


III II II


II II II







SECTION 6. SUMMARY AND CONCLUSIONS ........................

Sum m ary ............................................


109

109


Conclusions .......................................... 111

Limitations of the Study and Suggestions for Further Research ... .... .. 112


REFERENCES

APPENDIX A.

APPENDIX B.

APPENDIX C.


APPENDIX D.

APPENDIX E.


APPENDIX F.


APPENDIX G.


LIST OF COMMON METHYL BROMIDE FORMULATIONS ....

COMMERCIAL APPLICATION OF METHYL BROMIDE ......


114

124

129


ALTERNATIVES TO METHYL BROMIDE AND THEIR USE IN
FLORIDA ...... ....... ........................ 132

THE MARKET FOR FLORIDA FRUIT AND VEGETABLES .... 147

A MATHEMATICAL MODEL OF THE NORTH AMERICAN WINTER
VEGETABLE MARKET .. ........................ .. 157

A MATHEMATICAL MODEL OF THE WORLD MARKET FOR FLORIDA
GRAPEFRUIT .................................. 197

NEXT BEST ALTERNATIVES TO METHYL BROMIDE FOR FLORIDA
FRUIT AND VEGETABLES .......................... 201







ABSTRACT

Methyl bromide is a critical pesticide that is used in producing many fruit and vegetable

crops grown in Florida and the nation. It is a broad spectrum pesticide serving as an insecticide,

nematicide, herbicide and fungicide. The environment which prevails in Florida makes the use

of methyl bromide critical to the competitiveness of these crops in the U.S. and international

markets. The Environmental Protection Agency (EPA) declared in November 1993 that methyl

bromide was a Class I ozone depletor, and as such must be phased out of use by the year 2001.

Commodities analyzed in this bulletin included tomatoes, bell peppers, cucumbers, squash,

strawberries, watermelons and fresh citrus. Alternative chemical and non-chemical production

and marketing practices are discussed. Because no known alternatives exist that will effectively

substitute for methyl bromide, Florida is estimated to lose over $620 million in shipping point

value of fresh fruit, vegetables, and fresh citrus, worth over $1 billion in total sales in Florida,

and more than 13,000 jobs. Florida will reduce acreage by more than 43 percent if methyl

bromide is banned and no suitable alternatives are developed. Production of these crops will

cease in Palm Beach County and tomato production in Florida will decline by more than 60

percent. The primary beneficiary of this policy will be Mexico who, as a developing country,

will have 10 additional years to use methyl bromide in producing and marketing their crops.

Production will increase significantly in Mexico for all tomatoes (80 percent), bell peppers (54

percent), cucumbers (7 percent), and eggplant (143 percent).






ACKNOWLEDGENIENTS

We would like to acknowledge the support and assistance of several individuals who

contributed to the completion of this project. This project could not have been completed as

well or as thoroughly without their assistance.

We would first like to acknowledge the assistance of Drs. Joe Noling, Nematologist at

the University of Florida Citrus REC-Lake Alfred; George Hochmuth, Nutrition Vegetable

Specialist at the University of Florida Horticultural Sciences Department; Donald Maynard,

Vegetable Specialist at the University of Florida Gulf Coast REC-Bradenton; and Bill Stall,

Weed Control Specialist at the University of Florida Horticultural Sciences Department. These

gentlemen, along with Lorne Mathers, gave support that allowed this project to produce the

horticultural details of how methyl bromide worked and to identify the alternatives to and the

consequences of its removal. They helped in identifying alternative production practices and

choosing the alternatives that would be used if methyl bromide is banned. Their horticultural

knowledge contributed greatly to the success and results of this research.

We would also like to acknowledge the support of Scott Smith, Economic Analyst, Food

and Resource Economics Department, University of Florida, for his assistance in budgeting

crops and the alternatives to methyl bromide. Mr. Samual Scott, graduate research assistant in

the Food and Resource Economics Department, extended his M.S. thesis research and provided

estimates of demand flexibilities for eggplant, squash, watermelon, and strawberries.

Our thanks to Richard Kilmer and Richard Weldon, Food and Resource Economics

Department, University of Florida, who reviewed an earlier draft of this manuscript and made

several helpful suggestions.

Finally, we acknowledge that any errors in this document are the responsibilities of the

authors and not those who assisted in or funded the project.

vi








EXECUTIVE SUMMARY

Methyl bromide is an important chemical which is used in the production and marketing

of a wide range of agricultural products throughout the world. In Florida, it is used both as a

pre-plant soil fumigant and as a post harvest fumigant for many of the fruits and vegetable crops

produced in the state to control a wide array of pests. Methyl bromide has been identified as

a Class I ozone depleting chemical, and its production and use will be banned in United States

in 2001.

Methyl bromide is used as pre-plant fumigant for many of the fruit and vegetable crops

produced in central and south Florida. It is used in conjunction with plastic mulch and provides

an effective control for weeds, nematodes, and other soilborne pests in the production of

tomatoes, peppers, eggplant, cucumber, squash, strawberries, and watermelons. Methyl bromide

is also utilized as a post harvest fumigant to control fruit fly on fresh citrus shipped to other

citrus producing states. As Florida is a major supply region for many of the crops which benefit

from the use of methyl bromide, the proposed ban will affect both Florida producers and U.S.

consumers of fresh fruits and vegetables marketed in the November through May period.

In this study, a comprehensive review of previous work related to methyl bromide was

conducted. A survey of extension specialists in the production areas was utilized in conjunction

with the literature review to identify existing production systems and possible alternatives to

methyl bromide. After crop production systems had been delineated, further consultation with

horticultural scientists at the University of Florida provided detail on possible alternatives to

methyl bromide and the impact of alternative production practices on crop yields and production

costs.







It was recognized that the use of plastic mulch in conjunction with methyl bromide is the

primary production system employed by Florida farmers who produce tomatoes, peppers,

eggplant, and strawberries destined for the winter market in the United States. Cucumber,

squash, and watermelon may be produced as second crops which utilize the same plastic mulch.

It was also determined that methyl bromide provides effective control for nematodes, weeds, and

soilborne pests. It may also be applied with chloropicrin, which is an effective fungicide.

Alternative fumigants to methyl bromide include Vorlex, Vapam, and Telone. Each of these

alternative fumigants have disadvantages relative to methyl bromide which explains, in part, why

the use of methyl bromide dominates in the Florida fresh winter produce industry. A main

result from this component of the study is that production systems based upon plastic mulch will

survive in the absence of methyl bromide. Non-chemical alternatives such as steam or

solarization are experimental at this time. The use of crop rotations offers one plausible

alternative but is impractical in the east coast production area because of high land costs.

The use of methyl bromide as a post harvest fumigant was also analyzed. Fresh citrus

is the major crop on which post harvest fumigation is widely practiced. This is done to control

the possible presence of fruit flies in fresh fruit to be shipped to other citrus producing states.

Currently, all fresh citrus destined for the export market is not fumigated. No viable alternatives

could be identified for use in post harvest fumigation.

To conduct economic analyses of the impact of a ban of methyl bromide, two

mathematical models were developed. The first models the North American winter fresh

vegetable market. The second is a modification of an existing model of the world market for

Florida grapefruit.








The North American winter fresh vegetable market model included supply and demand

relationships for tomatoes, peppers,-eggplant, cucumbers, squash, watermelon, and strawberries.

The months included in the model are those months in which Florida is an important supply

region to the market. For tomatoes, peppers, eggplant, cucumbers, and squash, the model

spans the November through May period. Mexico is included as the alternative supply area for

tomatoes, peppers, eggplant, cucumbers, and squash for the November through May period.

Texas is a competing supplier of peppers in November and December. California is the

competing supplier of strawberries. Florida is active in the strawberry market from December

through March. No other region is a major supplier of watermelon in May. The North

American market is divided into four major demand regions whose central points were assumed

to be New York City, Chicago, Atlanta, and Los Angeles.

Analysis of a methyl bromide ban on Florida citrus growers was conducted in two parts.

First, a model of the Florida grapefruit market was modified to account for the methyl bromide

ban. It was assumed that a ban on post harvest fumigation of citrus would result in a loss of

the markets in other citrus producing states. This scenario was analyzed in the grapefruit model.

It was determined that fresh grapefruit would be reallocated to non-citrus producing states; there

would be no impact on processed grapefruit utilization. The analysis conducted for fresh

oranges, tangelos, and tangerines considered only the fresh market.

The results of the economic analysis are:

the loss of methyl bromide would have a devastating effect on Florida winter fresh
vegetable producers;

Florida production of tomatoes for the winter market will decline by 60 percent;

Florida will lose market share in both peppers (63%) and cucumbers (46%);








Eggplant will no longer be produced in Florida for the winter market;

All vegetable production in eastern Palm Beach county will cease; Dade county will no
longer produce tomatoes;

Lesser effects are projected for squash, which is not a major user of methyl bromide;

The Florida strawberry industry will suffer a major contraction of production (69%);

There will be a 40% decline in the production of double crop watermelons in Florida;

Both Mexico and Texas will expand production of vegetables; Mexican tomato
production will expand by 80%; its pepper production by 54%; its eggplant production
by 123%;

The economic loss to Florida is substantial. The FOB value of lost fruit and vegetable
production is $620 million;

The projected loss of FOB revenue to the Florida citrus industry is $13 million;

The total economic impact of a methyl bromide ban to the state of Florida is estimated
at approximately $1 billion and 13,000 jobs.

The economic analysis is based upon the best information currently available regarding

crop yields and production costs associated with alternative production systems. Further

research is needed to validate the assumptions made in the economic analysis.

The conclusion of the study is that the Florida winter fresh vegetable industry will face

dire consequences if new alternatives to methyl bromide are not identified before the ban of

methyl bromide is scheduled to take effect.








SECTION 1

INTRODUCTION



Methyl bromide is a broad spectrum pesticide used on a number of agricultural crops.

As a soil fumigant it serves as an insecticide, nematicide, herbicide and fungicide. It also serves

as a fumigant for stored commodities for protection against pests such as fruit fly and rodents.

Parties to the Montreal Protocol on Substances that Deplete the Ozone Layer (commonly referred

to as the Montreal Protocol) declared at their November 1992 meeting that methyl bromide had

an ozone depletion potential (ODP) of 0.7. This level is well above the 0.2 ODP required to

classify it as a Class I ozone depleter. The United States enacted the Clean Air Act in 1992.

The Clean Air Act requires that all Class I ozone depleting compounds be banned. The EPA

has informed the producers and users of methyl bromide that its production and importation will

be banned beginning January 1, 2001.

In Florida, methyl bromide has been important to the production of several fruit and

vegetables. 'Old land disease' became a problem for many farmers in the 1950's and 1960's

because of the buildup of pests in soils when individual fields were cultivated intensively for

several years. Farmers initially solved this problem by moving to virgin land. They would then

farm the land until old land disease set in, and then repeat the process by renting different land

to farm which had not been farmed recently. Land pressures from urban encroachment and

protection of the environment made this type of farming more difficult and new farming

practices had to be developed to take advantage of the declining agricultural land base.

McMillion (1972) and Volin and McMillion (1973) first demonstrated that the old land disease







complex could be controlled effectively by increasing the percent of chloropicrin injected with

methyl bromide. Tomato producers began using plastic mulch in combination with soil

fumigates in 1973. Other vegetable crops rapidly adopted this practice soon thereafter. As a

result, it was now possible to farm intensively without having to rotate into less intensive, lower

profit cropping systems for several seasons. In a subtropical environment which is conducive to

the rapid build-up of a wide array of economically important soilborne pests, methyl bromide

has proven to be a consistent, effective means of control for these pests.

The importance of methyl bromide as a fumigant and the environmental problems

associated with its use have led to a current critical situation in the Florida agricultural industry.

Because of the success farmers realized in using methyl bromide since the 1960's, little research

has been conducted with regard to the identification and evaluation of alternatives which could

now be used as effective substitutes to methyl bromide. The alternative identified as having the

most potential for succeeding methyl bromide, Vorlex, (USDA, NAPIAP, 1993) has been

voluntarily removed from the market by its manufacturer (NOR-AM Chemical Company)

because of the expense required to register the compound with the U.S. Environmental

Protection Agency (EPA)., This action makes Vorlex unavailable to farmers and others. Other

chemical and non-chemical alternatives have been identified, but those alternatives are not as

economically effective as methyl bromide in controlling the broad spectrum of pests that can

affect Florida growers.

Recently a USDA NAPIAP (1993) report estimated the impact of removing of methyl

bromide from agricultural use. That study suggested that removal of methyl bromide would

result in an economic loss of approximately $850 million to $1 billion to U.S. agriculture,







depending on whether Vorlex was available as a substitute. Another $500 million loss would

be imposed on imported items that could not use methyl bromide for quarantine treatment. Food

products produced in the U.S. that would be impacted the most included fresh market tomatoes

($160 million with Vorlex/ $340 million without), peppers ($130 million), strawberries ($110

million), cucumbers ($72 million), melons ($29 million), fresh citrus ($25 million), and eggplant

($12 million). The only other food item impacted by more than $1 million dollars was grapes

($3 million).

The products identified in this report are some of the leading agricultural products grown

in Florida. Florida grew 134,550 acres of these items (excluding citrus) which sold for a total

shipping point value of more than $1 billion in the 1992/93 season (Table 1.1). Fresh citrus

sales amounted to an another approximately $600 million.



Table 1.1. Acreage and value of selected fruits and vegetables grown in Florida, 1992/93.
Commodity Acres Value ($1,000)
Cucumber 15,800 65,699
Eggplant 2,150 13,568
Peppers 21,100 179,383
Tomatoes 48,400 626,048
Strawberries 5,100 102,724
Watermelons 42,000 66,600
Total 134,550 1,054,022

Source: FASS, Florida Vegetable Summary 1992-1993.







Because the food crops showing the potential for the most impact from the removal of

methyl bromide are also some of the same crops which are important to Florida, the issue of

removing methyl bromide is especially important to Florida. The primary objective of this

report is the estimation of the economic impact of the removal of methyl bromide on the Florida

agricultural sector and consequently on the economy of the State of Florida.



Organization of this Report

This report is organized to first (Section 2) provide a historical background on the

development and use of methyl bromide in the Florida fresh produce industry. Alternative

chemical and non-chemical production systems that do not use methyl bromide are presented in

Section 3. A discussion of the crops that are important to Florida that use methyl bromide

follows (Section 4) with a presentation of production practices used for each crop. Finally, the

economic consequences of a methyl bromide ban are estimated and presented (Section 5) and

conclusions are drawn from the analysis (Section 6). References and appendices that support

the analyses follow.







SECTION 2

THE EVOLUTION AND USE OF METHYL BROMIDE IN THE

VEGETABLE AND CITRUS INDUSTRIES



Methyl bromide is marketed as a broad spectrum pesticide that acts as an insecticide,

nematicide, herbicide, and fungicide when used in the fumigation of soils (Noling and Overman,

1988). The chemical plays an important role when used as a preplant fumigant which reduces

soilborne pest populations and enables continued cropping of the same land year after year. It

is also used as a fumigant in greenhouses, transplant beds, and potting soils. Methyl bromide

is also used as an acaricide and rodenticide in the treatment of nondwelling space and packaged

materials. The intended purpose for the chemical dictates which formulation of the compound

is used (refer to appendix A for examples of various formulations of methyl bromide, their

restricted uses, and their listed items of control). Methyl bromide is injected into soil as a

liquid, however, once in the soil the chemical converts to a gas moving through open soil pore

spaces (Noling, 1993b). This chemical is registered as a restricted use pesticide due to its acute

toxicity (refer to Table 2.1 for properties of methyl bromide).

Methyl bromide is produced by both natural and man-made processes (IFAS-Chemically

Speaking, April, 1992). The ocean is reported to be the primary source of naturally-made

methyl bromide (Sze and Ko, 1991). Man-made methyl bromide is a product derived from the

treatment of brine, which is pumped from underground sources, such as natural brine or oil field

brines. Processing methods require that the brine be treated with chemicals or undergo heat

reaction to obtain bromine. Bromine is then used to produce methyl bromide (Kent, 1974).







Table 2.1 Physical and chemical properties of methyl bromide


COMMON SYNONYMS:


Bromomethane

M-B-C Fumigant


Embafume

Monobromomethane


FORMULA: CH3Br

MOLECULAR WEIGHT: 94.95

BOILING POINT AT 1 atm: 38.5F = 3.60C = 276.8K

FREEZING POINT: -135F = -93*C = 180k

CRITICAL TEMPERATURES: 376*F = 191 C = 464k

SPECIFIC GRAVITY: 1.68 at 20*C (liquid)

LIQUID SURFACE TENSION: 24.5 dynes/cm = 0.0245 N/m at 15C

VAPOR (GAS) SPECIFIC GRAVITY: 3.3

RATIO OF SPECIFIC HEATS OF VAPOR (GAS): 1.247

LATENT HEAT OF VAPORIZATION: 108 Btu/lb = 59.7 cal/g =

2.50 x 105 J/kg


HEAT OF COMBUSTION: -3188 Btu/lb = -1771cal/g = 74.5 x 105 J/kg


Source: Weiss (1986)








The chemical is manufactured and distributed in the United States, Israel, United Kingdom,

Ireland, Germany, Greece, Yugoslavia, The Netherlands, Spain, Italy, Japan and France.

Methyl bromide is sold in various formulations. These can range from 100% methyl

bromide to a mixed formulations with various proportions of chloropicrin. Due to the odorless

characteristic of methyl bromide, low concentrations of chloropicrin (2 percent) are used as a

marker for detection of escaping methyl bromide fumes (Noling, 1993b). Combined with methyl

bromide, chloropicrin at higher concentrations (such as 33%) serves to enhance fungicidal

activity to aide in the control of soilborne diseases.

When used for treatment of grain storage structures, buildings, ships, cargos, and other

listed structures, methyl bromide is effective as an acaricide and rodenticide. Some of the pests

controlled include granary weevils, cockroaches, and beetles. When the chemical is used in crop

production, it is considered a nematicide, fungicide, insecticide and herbicide. Important

nematodes controlled by methyl bromide include root knot and stubby root nematode (Overman

and Jones, 1980). Examples of diseases that methyl bromide controls are Fusarium,

Verticillium, Rhizoctonia and Pythium. Insects controlled include wireworm and grubs. As a

herbicide, methyl bromide is important in the control of many different weeds such as nutsedge,

pigweed and nightshade.



Historical Overview

Development and Use of the Chemical

"Old land disease", a well documented phenomenon in tomato production, is caused by

the increase in pests such as weeds, nematodes, and plant pathogens due to continuous mono-

cropping of the same land year after year. The population of pests unique to these crops builds

up in the soil over a period of time. When additional land is available, farmers can rotate to

7







other fields that have not been used for two or three years, thus reducing the incidence of those

pests that negatively affect the crop (Bewick, 1989).

Due to increased competition in Florida for agricultural land by urban development and

environmental pressures, increased land prices and decreased land availability have resulted in

farmers searching for alternative methods of pests control (Bewick, 1989). According to

Johnson and Feldmesser (1987), the first use of a fumigant may have been as early as 1872

where experiments proved the efficacy of carbon disulfide as a nematicide. Carbon disulfide

was used in grape production in France, however, it was discontinued due to the development

of pest resistant rootstocks. Chloropicrin was first tested as a soil fumigant in 1919. Research

was then initiated in California and Hawaii. Later it was used as a soil fumigant in pineapple

production in Hawaii. Large quantities of chloropicrin were made available by the United States

government and were targeted for use in seed beds, greenhouses, and specialty crops. When

supplies diminished, commercial use of this chemical decreased.

A marked increase in research on the use and efficacy of soil sterilants was conducted

during the 1950's. During this time, it was found that methyl bromide and chloropicrin gave

the most effective, consistent control of soilborne pathogens (Williamson et. al. 1955).

Research on application methods during the 1960's found that the use of vinyl or

polyethylene films, applied after soil injection of methyl bromide, increased pest control

efficacy. In 1965, Geraldson et al. (1965) introduced the raised bed, methyl bromide, plastic

mulch culture to Florida tomato producers (Bewick, 1989). The use of plastic mulch also

proved to reduce leaching of fertilizers, to retain soil moisture and to increase weed control over

a longer period of time (Martinkovic and Nesheim, 1993). However, system complexity and

the time and expense involved in field removal of plastic mulch resulted in slow adoption of this

technique during the early 1960's.







The 1970's saw a dramatic increase in the use of the whole systems approach (plastic

mulch and fumigation). A majority of the tomato producers in Florida began using either plastic

mulch or a combination of plastics and fumigation (Bewick, 1989).

"The systems approach was developed for tomato production in south Florida, but

by 1978 it had become an integral part of tomato production in every part of the

state. By 1978, 81% of tomato fields were mulched and 64% of tomato fields

were fumigated. Of those fields that were fumigated, 94% were mulched. Six

soil fumigants most frequently used were: methyl bromide (67% methyl bromide

+ 33% chloropicrin), Vorlex, Vapam, Telone, EDB and DBCP. Of these, the

first three are broad spectrum, and the last three are more specifically

nematicides" (Bewick, 1989 p. 66).

Of the six soil fumigants listed, methyl bromide, Vapam and Telone are the only remaining

chemicals currently available.


Methyl Bromide in the Soil

The chemical reactions of methyl bromide (MB) occurring in the soil are important to

understanding the effectiveness of methyl bromide. As a soil fumigate methyl bromide is

applied as a liquid via tractor drawn chisels or shanks six to eight inches deep in the soil. Due

to its high vapor pressure, it volatilizes rapidly and moves through the soil by mass flow and

then by diffusion (Munnecke and Gundy, 1979). Soil movement of gaseous phase methyl

bromide is specifically affected by soil moisture content. Methyl bromide follows a path of least

resistance. If soil moisture is too low, unobstructed air passages will allow methyl bromide to

rapidly diffuse out of the soil and be lost to the atmosphere. If the soil is too wet, movement







of the fumigant through the soil pores will be blocked and result in reduced effectiveness, due

to lack of movement and dilution of the chemical by the presence of water (Munnecke and Van

Grundy, 1979).

Soil type has also been found to influence the effectiveness of soil fumigation uses of

methyl bromide. Munnecke and Gundy (1979) stated that the more coarse and less compact the

soil, the more effective the fumigant is. Goring (1967) found that clays can absorb fumigants,

however, organic matter was implicated as the major source of absorption in the soil. Thus,

without an increase in application rate, high levels of organic matter can negatively influence

the effects of fumigation (Munnecke and Gundy, 1979).

Soil moisture, as it affects organisms in the soil, is an important factor that influences

a fumigant's effectiveness. Munnecke, et al. (1959) found that at higher levels of relative

humidity, there was increased uptake of methyl bromide into the spores of Alternaria solan

resulting in enhanced efficacy. In other studies, temperature was demonstrated influence to the

effectiveness of fumigants. Munnecke and Bricker (1978) and Kenaga (1961) found that when

methyl bromide is applied under warmer temperatures, there was an observed increase in

effectiveness.

Overall, plants have been observed to grow better in soils that have been fumigated.

Improved plant growth is due to the reduction in soilborne pest populations and/or disease

pressures, such as fungal pathogens, insects, nematodes and weeds. Exceptions, however, do

occur where plants do not produce or grow well in fumigated soils (Munnecke and Gundy,

1979). In some cases, poor growth responses occur due to reduced mycorrhizal propagule levels

in soil. Mycorrhizae are important in the uptake of some elements such as phosphorous. This







problem was especially prominent in citrus seed beds, where plants appeared chlorotic and

stunted (Tucker and Anderson, 1972). Another reason for unfavorable growth response in some

plants to methyl bromide fumigation is the accumulation of bromide ions in soil (Gentle et al.,

1989). Accumulation of these ions can often be corrected by leaching via irrigation.


Methyl Bromide as a Potential Contributor to Ozone Depletion

The ozone is a layer of atmosphere located approximately 9-21 miles from the surface

of the earth. This layer is important in reflecting ultraviolet rays and reducing the loss of heat

from the earth (Villee et al., 1989). There are several chemicals that have been implicated in

the possible destruction of ozone, one of which is methyl bromide.

There is considerable uncertainty and controversy associated with the identification of

sources of atmospheric bromine compounds. There are several reasons for uncertainty

associated with estimates derived from the calculations of atmospheric bromine compounds,

including the calibration of measurements, identification of sources and sinks, and the inter-

relationship between removal of atmospheric methyl bromide and contributions from known and

unknown sources (Watson and Albritton, 1991a).

Both natural and anthropogenic sources have been implicated as significant contributors

of methyl bromide in the atmosphere. The contributions of various sources of methyl bromide

to total atmospheric concentrations have not been clearly characterized, however, anthropogenic

sources have been implicated (Watson and Albritton, 1991a). Based on recent estimates,

approximately half of the total methyl bromide used for soil fumigation is thought to find its way

into the upper atmosphere. This equates to an estimated 30,000 metric tons per year

(Chemically Speaking, 1992b). Methyl bromide is also produced by natural means, and there







is evidence implicating the oceans as a major contributor to stratospheric concentrations of

methyl bromide (Sze and Ko, 1991).

Ozone depletion potential (ODP) is a factor which determines how much a chemical

contributes to the depletion of the ozone. As a result of the U.S. Clean Air Act of 1990, a

chemical with an ODP of 0.2 or higher must be phased out of production and use by the year

2000 (Chemically Speaking, 1992b). Based on knowledge about removal of methyl bromide

from the atmosphere, the atmospheric life expectancy of methyl bromide has been calculated to

be 1.6 years, with an uncertainty factor of about 4 (Sze and Ko, 1991).

"Methyl bromide emissions from fumigation application may have accounted for

1/10 to 1/20 of the current global ozone loss, according to the modeling

calculations discussed at an international science workshop in Washington, D.C.

convened at UNEP's request" (Chemically Speaking, 1992b).


Legal Developments Surrounding Methyl Bromide

The Clean Air Act of 1990 (CAA) is a U.S. federal law, whose primary objective is to

maintain and to enhance the quality of the earth's atmosphere. Title VI of the CAA, called the

"Stratospheric Ozone Protection", lists ozone-depleting substances in either Class I or Class II.

If the substance is classified as Class I, then its ozone depletion factor is greater than 0.2, and

the substance will be required to be phased out by the year 2000. However, if the substance

falls under Class II, then it has a ozone depletion factor less than 0.2 and will be required to be

phased out by the year 2015 or 2030 depending on the situation.

The Clean Air Act allows anyone to petition the Environmental Protection Agency (EPA)

in order to list a substance to be classified as a ozone depletor (EPA, 1993). After being







petitioned, the EPA is required to respond to the petition within 180 days. There are certain

exemptions for special cases of known ozone depletors, however the specifications under which

methyl bromide would qualify are unclear.

On December 3, 1991 the Natural Resource Defense Council (NRDC), the Environmental

Defense Fund (EDF) and the Friends of the Earth (FOE) petitioned the EPA requesting that EPA

add methyl bromide to the list of class I ozone depletor substances, reduce production of methyl

bromide by fifty percent by 1992 and accelerate phaseout of methyl bromide by January 1, 1993.

"The petition also requested that EPA order this accelerated phaseout of

methyl bromide based on the (EPA) Administrator's emergency powers

under section 303 of the (Clean Air) Act to protect public health or

welfare or the environment" (EPA, 1993 p. 15030).

The Methyl Bromide Working Group is an industry group comprised of the three major

methyl bromide manufacturers. The Methyl Bromide Working Group responded to this petition

by submitting two letters to the EPA Administrator regarding the addition of methyl bromide

to the list of ozone-depleting substances. The first letter emphasized the lack of evidence

implicating anthropogenic sources of methyl bromide in the destruction of the ozone and

maintained that this lack of evidence does not warrant emergency action by the Agency under

section 303. The second letter called for the denial of the petition again citing the scientific

uncertainty of the impact of anthropogenic sources of methyl bromide on the atmosphere (EPA,

1993).

At the fourth meeting of the Montreal Protocol, an international agreement between

member nations to oversee the manufacturing and trade of ozone depleting substances, members







agreed to: (1) amend the Protocol to add methyl bromide to the list of potential ozone depletors

as a controlled substance, (2) adopt an Ozone Depletion Potential (ODP) of 0.7 for methyl

bromide, and (3) freeze its production (with exemptions for quarantine and pre-shipment use)

at 1991 levels beginning in 1995.

"The Parties adopted the recent scientific assessment of 0.7 for the ODP,

acknowledging this as the best estimate despite the uncertainties related to this

estimate" (EPA, 1993 p. 15030).

This amendment was to become effective January 1, 1994, if twenty parties (countries)

ratified the amendments. However, if twenty parties had not ratified the amendments by the

deadline, the amendments were to enter into force ninety days after the twentieth party ratified

the amendments (EPA, 1993).

In response to the aforementioned petition filed by the Methyl Bromide Working Group,

the EPA rejected the phaseout schedule proposed by NRDC, FOE, and EDF. The EPA

indicated that, because of limited information regarding possible substitutes for the chemical

methyl bromide, the most stringent schedule it can propose includes a production and

consumptive freeze at 1991 baseline levels beginning January 1, 1994, along with a total

phaseout by January 1, 2001.

The EPA announced on the 19th of January, 1993, a proposal to phase out or limit

production and use of chemicals believed to be involved in stratospheric ozone depletion. This

proposal would apply to chemicals produced domestically and imported. Companies may

continue use through available supplies or recycling after the deadline, however, U.S. companies

may produce above levels set by the EPA in order to supply the essential domestic requirements







of developing countries. Developing countries may continue use of chemicals until the year

2010 (Chemically Speaking, 1993).


Methyl Bromide and Safety/Health Concerns

Methyl bromide is listed as a restricted use pesticide due to acute toxicity. According

to the specimen label for methyl bromide, it is for retail sale to, and use only by, Certified

Applicators, or persons under their direct supervision, and only for those uses covered by the

Certified Applicator's certification. The chemical is a gas which is colorless, tasteless, and

odorless unless in high concentrations. The chemical can be applied as a liquid, however at

room temperature, the chemical converts into a gas which can be inhaled and result in

respiratory problems, which is considered to be the most common and serious injury associated

with methyl bromide. Symptoms associated with methyl bromide may not occur for several

hours or days because the chemical is not found to be irritating to the eyes or the upper

respiratory tract, unless substantial amounts are inhaled into the lungs. Inhaling substantial

amounts can lead to irritation of the cells lining the lungs which can result in pulmonary edema

(fluid in the lungs), sometimes leading to death (Noling, 1993b). Methyl bromide is not as

effectively absorbed through the skin, however it can cause skin blisters and enter the circulatory

system through absorption of the skin. A range of 8,600 to 60,000 parts per million (ppm) have

been found to be fatal in humans (Noling 1993b). Therefore, threshold concentrations have been

established as a safety guideline prior to entering into a treated area. According to the specimen

label, if there are amounts of 5 ppm or greater present in the air, then entry into the treated

region should be delayed for 48 hours.







Chloropicrin can be used at low concentrations as an odorant in conjunction with methyl

bromide for detection of escaping fumes of methyl bromide. Chloropicrin is an irritant to the

eyes and respiratory tract and allows detection prior to inhalation of substantial quantities of the

chemical. It has been recommended that chloropicrin (not less than 2%) be used in conjunction

with methyl bromide for detection of atmospheric methyl bromide (Noling, 1993b).


Application of Methyl Bromide as a Soil Fumigant

In preparing a field for subsequent use of methyl bromide, plowing and disking should

be performed to turn under old crop residue in order to reduce detrimental soil organisms and

to allow for decomposition of crop residue. Disking ensures that large clods of soil are broken

down and aids in leveling the field for ease of future activities such as bed formation. Bed

formation can be done using a disc hiller or bedding disc. The soil should be analyzed for pH

adjustment and fertilizer requirements (Hochmuth, 1989a). Bed widths generally range from 24

to 36 inches depending on the crop and irrigation type. The height of the bed is approximately

8 inches. The number of beds between irrigation-drainage furrows varies from one to four,

depending on the soil type and drainage capabilities of the land.

Methyl bromide for preplant fumigation is sold in pressurized gas cylinders, in various

formulations with chloropicrin. The chemical is delivered via a positive pressure system using

nitrogen gas for pressure. Methyl bromide is injected into the soil as a liquid to a depth of 8

to 12 inches using tractor drawn chisels or shanks spaced no more than 12 inches apart. The

liquid then vaporizes and diffuses through the soil from the point of injection. One or more

shanks per bed may be required depending on the width of the bed. Rates of application can

range from 100 pounds to over 400 pounds of active ingredient per acre depending on the







purpose and field conditions (for rates of application for methyl bromide, refer to appendix B

for formulation and application rates for a desired crop).

Methyl bromide is used with chloropicrin in various formulations as a preplant soil

fumigant. At low concentrations (up to 2%), chloropicrin is used as a marker for detection of

escaping fumes of methyl bromide. At higher concentrations, such as 33%, chloropicrin is used

as a fungicide (Noling and Overman, 1988). In Florida, two formulations are primarily used:

Brom-O-Gas (98% methyl bromide and 2% chloropicrin) and Terr-O-Gas (67% methyl bromide

and 33% chloropicrin).

Immediately following bed formation, a polyethylene tarp (plastic mulch) must be

applied. This mulch serves to reduce the loss of methyl bromide to the atmosphere as it

vaporizes in addition to other horticultural benefits. In situations where plastic mulch is a

component of the whole-systems approach, the plastic mulch is installed and remains throughout

the life of the crop. There are several types of plastic mulch, depending on the use or purpose

and time of the year installed. Growers may use plastic mulch that is gray, clear, white, black,

or white laminated on black. For example, in the spring, the use of black plastic can raise soil

temperatures to levels which are conducive to young plant growth. However, during the fall,

the soil temperatures are already warm and the use of white plastic is preferred, because white

plastic reflects light, resulting in cooler soil temperatures, as compared to black (Decoteau et

al., 1989).

The thickness of plastic can vary from .25 to 1.5 millimeter or thicker. Thicker plastic

mulches correspond to greater decreases in atmospheric loss of methyl bromide. Other

advantages of plastic mulch include increased weed control, increased moisture retention, and






decreased fertilizer leaching (Hochmuth, 1988a). The width of the plastic mulch can range from

48 inches to up to 72 inches, depending on the equipment used and type of crop planted. In

regions where plastic mulch is used, a grower may plant a second crop on the same field

following the first crop (generally called doubled cropping), thereby using resources that remain

from the first crop. These resources can include residual chemicals including fertilizer,

insecticide, etc., and plastic mulch.

"If properly managed, double cropping can allow a grower to produce a second

crop, with a short turn-around time, with minimum inputs compared to the first

crop" (Hochmuth, 1992, p. 1).

When choosing a second crop, a grower may consider a crop that (1) has a short growing

season, (2) requires low input of fertilizers, and (3) is known to do well on plastic (Hochmuth,

1992). However, the choice is often dictated by market demands and price. Recommendations

for a second crop include vine crops such as watermelon, cucumber, pumpkins, and squash

following primary crops such as strawberry, peppers, or tomatoes.

Cultural practices used in a double cropping system are important. Removal of the first

crop debris, following final harvest of the first crop, is important for reduction of insects and

disease organisms that may be associated with the primary crop. This may be accomplished by

spraying a herbicide chemical to kill the upper portion of the plant or mowing prior to spraying

to enable the chemical to more effectively kill the plant. Some contact herbicides such as

paraquat do not translocate through the plant and kill the root system. In this situation, some

fumigant chemicals can be used to effectively kill the primary crop, including the root system.








Application of fumigant chemicals (labeled for injection) can be done using a drip irrigation

system if this system is already present.

A second crop can be planted by either direct seeding or transplants. Seeding can be

accomplished by hand, however there are several machines available that can cut a hole in the

plastic and install the seed or plug-mix seed combination. Transplants can be installed via hand

or machine (Hochmuth, 1992).

The use of a double-cropping system often requires the application of additional fertilizers

for the second crop. There are several methods that can provide supplemental fertilizers such

as cutting holes in the plastic to apply either liquid or dry fertilizers, applying fertilizers via

irrigation (e.g., drip system) or using a liquid injection wheel (Hochmuth, 1992).

A double cropping system of pepper and cucumber production in Palm Beach County,

Florida is common. The pepper crop is considered the primary crop and is generally produced

using full-bed plastic mulch with seepage irrigation. This system generally requires that all soil

additives such as fumigants and fertilizers be added prior to application of plastic mulch. If the

plastic mulch from the first crop is in satisfactory condition, it is often re-used for a second crop

of cucumbers. It should be recognized that methyl bromide is not reapplied to the second crop.

The advantages of planting a second crop are that it (a) helps provide additional returns to fixed

costs beyond the variable cost of producing the second crop (e.g., land rent) and (b) re-uses

plastic mulch and other inputs (i.e., fumigant fertilizers, chemicals, and irrigation systems) that

would otherwise need to be applied if not present from the first crop.







SECTION 3

CHEMICAL AND NON-CHEMICAL ALTERNATIVES TO METHYL BROMIDE USE

In this section possible alternatives to methyl bromide are discussed. It is important to

remember that some of these alternatives should not be considered viable alternatives to methyl

bromide at the present time, but rather construed as researchable alternatives. It is also

important to remember that some of these methods may take several years to reduce pest

populations to levels that enable the grower to produce crops that may be comparable to yields

experienced when methyl bromide is used.

There are numerous fumigant and non-fumigant alternatives that include the use of

chemicals, cultural practices, biological controls, heat, and the concept of integrated pest

management. Currently, some of these techniques are being evaluated and hold promise of

being viable alternatives. However, none of the alternatives identified currently provides the

efficacy exhibited by methyl bromide.

The first category of alternatives includes fumigant chemicals Basamid, Vorlex, Vapam,

Telone, Chloropicrin, and reduced amounts of methyl bromide. The second category includes

non-chemical alternatives including crop rotation, cover crops, heat treatment, flooding,

biological controls, host plant resistance, and fallow land.


Chemical Alternatives to Methyl Bromide
Basamid-Granular

Basamid-Granular is classified as a soil sterilant containing the active ingredient

dazomet. In some studies, it has been shown to be effective in the control of fungus, weeds,

nematodes, and soil insects. Basamid has been used in Europe for over 20 years, however this








chemical has only limited EPA registered uses in the United States. According to McElroy

(1985), it is used for preplant control of most weeds, nematodes, and soil fungi in tobacco

seedbeds, forest tree seedbeds, and ornamental propagating beds (for a brief review of

information derived from the specimen label for Basamid-Granular, refer to Appendix C-l).

Upon application to the soil, dazomet reacts with water and chemical components in the

soil to produce a sterilizing agent called methylisothiocyanate (MITC) (Neumann et al., 1983).

When dazomet contacts water in the soil, the chemical breaks down to MITC, resulting in the

formation of a gas which then diffuses throughout soil. Most recommended uses suggest that

application be done several months prior to planting to ensure the chemical is not present at time

of planting. Otherwise, some of the chemical may still be residual in soil, resulting in crop

damage. This is often considered a limiting factor due to time constraints for planting crops.

To be effective, Basamid-Granular must be soil incorporated to ensure uniform soil distribution.

The advantages of dazomet include its ease of application which can be done in one step

and its low environmental impact with no substantial volatile compounds being released into the

atmosphere. Also, application of the granular form is considered low risk to applicators due to

the nature of the chemical being inert until activated by water in soil. Another advantage is that

the control exhibited by this chemical is considered broad in spectrum (O'Brian and

VanBruggen, 1990).

Some of the disadvantages are that the chemical is less predictable, and it can result in

spotty effectiveness if it is not incorporated well and distributed evenly throughout the soil.

Planting before the soil is properly aerated can result in crop phytoxicity.






Vorlex


Vorlex is a restricted use pesticide that can be applied as a preplant soil fumigant, for

both the field and greenhouse, for control of soilborne diseases, nematodes, weeds and insects.

Vorlex is comprised of two active ingredients, 1,3-dichloropropene and methylisothiocyanate or

MITC (Vorlex specimen label). When applied properly, Vorlex vaporizes and moves through

the soil by diffusion. The Vorlex specimen label states that it is cleared for use in all vegetables

and strawberry production (for a brief review of information derived from the specimen label

for Vorlex, refer to Appendix C-2).

Tarping the soil (plastic mulch) is not required but it can be considered an advantage

when using Vorlex as a fumigant. Increased efficacy is exhibited when plastic mulch is used.

Vorlex. was indicated as being the next best alternative to methyl bromide due to increased

control of diseases, weeds, nematodes, and insects as compared to other alternatives (USDA,

NAPIAP 1993). However, Vorlex still does not exhibit the kind of control demonstrated by

methyl bromide. Another disadvantage of Vorlex is that it requires a longer waiting period prior

to entering the field, and therefore may interfere with crop planting dates.

The manufacturer of Vorlex (NOR-AM Chemical Company) requested a voluntary

removal of Vorlex from registration with the EPA in November, 1991. The EPA responded in

August, 1992, with approval of cancellation for registration of Vorlex. Vorlex was classified

by the EPA as a List B re-registration product which includes products that are used in the

production of food. This type of classification requires numerous, costly studies for EPA

registration. The research studies for Vorlex were considered old enough for the EPA to require

new studies. The manufacturer examined the market share of Vorlex and the cost of new studies







in order to conform to EPA standards, and concluded that it was not economically in their best

interest to continue sale and distribution in the United States. Another factor that played a role

in their decision to withdraw registration of Vorlex is that the chemical comprises only a small

portion of their business. At the time of the announcement of removal of Vorlex, several

companies approached the manufacturer to take over the division for Vorlex sale and

distribution, however, after evaluation of the situation regarding the economics and the cost of

new studies, these companies chose not to pursue the opportunity.

The manufacturer requested that EPA consider (a) registration of Vorlex as a minor use

chemical and (b) possible flexibility regarding the studies required for re-registration. EPA

responded by recommending that Vorlex be viewed as a new product (since it had been

voluntarily removed from registration) requiring approval by the registration division of EPA

instead of consideration by the re-registration division. If the EPA were agreeable to flexibility

in registration requirements and the economic situation favored the production of Vorlex (i.e.,

removal of methyl bromide from the market), the manufacturer might consider the possibility

of appropriate testing required for registration of Vorlex as a minor use product.


Vapam

Metham sodium, also known as Vapam, can be applied to the soil as a preplant, soil

fumigant for control of soilborne pathogens such as nematodes, weeds, fungi and insects.

Metham sodium is considered a water soluble, alkaline chemical. When combined with water,

which is acidic in comparison with metham sodium, the chemical becomes unstable and

decomposes to its active form of methylisothiocyanate (MITC). Once the chemical is placed in

the soil, MITC will volatilize from a liquid to a gaseous phase which enables it to flow






throughout the pores of the soil. However, MITC has a high affinity for the liquid phase;

therefore, the chemical does not move as readily through the soil as does methyl bromide

(Noling, 1991).

There are several factors that influence the efficacy of Vapam when applied to the soil.

Soil temperature and moisture play an important role in the conversion of metham sodium to

MITC. If the soil temperatures are too high and soil moisture is low, conversion is increased,

and the chemical may diffuse out of the soil too quickly, not allowing for an accumulation of

the chemical in the soil and effective control. If the soils are too wet and temperatures are cool,

the rate of decomposition to MITC is decreased. Under this condition the chemical cannot

accumulate in the soil to levels that are needed for effective control. If temperatures are low

or excessive water is applied after application of the chemical, the MITC may remain in the soils

longer than desired and result in delayed planting (Gerstl et al., 1977).

Several studies have also shown that soil type influences available MITC. Gerstl et al.

(1977) found that soils high in organic matter or clay incurred a delay in the amount of MITC

available to diffuse throughout the soil. Thus, for effective results, clay soils or soils high in

organic matter can require higher initial concentrations of Vapam.

For field application, Vapam can be applied using a chisel or an irrigation system. For

application via chisel, it is recommended that soil temperatures at 3 inches in depth are in the

range of 60 to 90 degrees Fahrenheit. Soil moisture should be approximately 50 to 80% of field

capacity. Rates of application need to be adjusted depending on environmental and field

conditions (Noling, 1993d). Vapam has been commonly applied via chisel injection, placed







approximately 6 inches apart. For effective results, one must treat 50% of the bed, which would

require two chisels per bed.

Due to the water solubility of Vapam, it is also labelled for application through overhead

irrigation. A study conducted by Sumner (1988) found increased efficacy against Rhizoctonia

soani and Pythium sp. when metham sodium was applied via overhead irrigation, as compared

to chisel application for a fall crop of turnip, kale, mustard and collard. However, reduced

control of root diseases and decreased plant stand in the spring crops of snap bean, okra,

cucumber, tomato, and pepper were also observed. Increasing application rates resulted in

improved control of soilborne diseases such as Pythium WS., Fusarium Wp. and saprophytic

fungi.

Chemical application of Vapam via drip irrigation is a form of chemigation (Haman et.

al., 1990). This method requires that the metham sodium be premixed prior to injection and

continuously supplied at specific locations for a period of time. There are several factors that

influence chemigation for pest control, including emitter spacing, type and length of irrigation

tubing, openings in the plastic which can allow diffusion into the atmosphere, and

soil/environmental conditions (Noling, 1993d). Overman et al., (1987) compared methyl

bromide (67%) plus chloropicrin (33%) injected via shanks 30 cm apart prior to plastic

application, to metham sodium injected via one drip line per bed. This study was conducted for

three seasons and found that yields for 'Sunny' tomato variety increased for both treatments,

however, by the third season yields were collected only from the methyl bromide-chloropicrin

plot. The area treated with metham sodium was desiccated with Fusarium wilt and root knot

nematode.







One advantage of Vapam is that it can be applied through an irrigation system.

However, soil temperature and moisture can dramatically influence the effectiveness of this

chemical. In addition, another major disadvantage of Vapam is the waiting period prior to

entering the treated area, which is dependent on environmental conditions. Planted crops will

incur damage, or be killed, if the chemical is still in the soil at the time of planting (Noling,

1991). Finally, Vapam is not as effective in control of diseases and nematodes when compared

to methyl bromide (Overman et al., 1987). Erratic or reduced control by Vapam is a common

occurrence, and more material may be required to approach desirable levels of control. As a

result of increased amounts of Vapam applied for effective control, the question arises as to how

much leaches through the soil and enters the water table (for a brief review of information

derived from the specimen label for Vapam, refer to Appendix C-3).


Telone II and Telone C-17

Telone II is a restricted use pesticide, which contains the active ingredient 1,3-

dichloropropene. This chemical can be used in crop production of eggplant, tomato, pepper,

strawberry, melon, cucumber, and citrus, as well as other crops. Telone C-17 is a multi-

purpose, preplant soil fumigant containing 77.9% 1,3 dichloropropene and 16.5% chloropicrin.

This chemical can be used for control of nematodes, soilborne fungi, and weeds, for some high

value field and vegetable crops (Dunn and Noling, 1993). The chloropicrin (16.5%) controls

some soilborne fungi, but not Sclerotonia or Rhizoctonia species.

Information regarding water contamination remains unclear. The manufacturer suspended

sale of Telone in south Florida prior to fall 1993, although it could legally still be used in south

Florida. Telone is currently sold and distributed in south Florida on a limited basis, and it is







simultaneously undergoing research for information regarding questions about safety and

contamination.

Environmental conditions are important for effective control with Telone. Youngson

(1982) found that Telone II was more readily leached from sandy soils than loam soils. Turner

(1970) discussed the influence of air space in the soil upon the effectiveness of Telone II. As

water is added to the soil, the amount of air space is decreased. This resulted in an observed

decrease in efficacy for nematode control, due to the decreased movement of the fumigant

through the pore space. It is advisable to apply the chemical during the fall, when drier

conditions exist, which allows the chemical to diffuse through the soil for increased efficacy.

This can be a limiting factor when considering planting dates and delayed use of the field (for

a brief review of information derived from the specimen labels for Telone II and Telone C-17,

refer to Appendices C-4 and C-5).


Chloropicrin

Chloropicrin is mixed in varying formulations with methyl bromide. At low

concentrations this chemical is primarily used as a marker for escaping fumes of methyl

bromide. Use of this chemical by itself, as a soil fumigant, is cost prohibitive. However, due

to its fungicidal properties, chloropicrin when mixed with methyl bromide at higher

concentrations is effective in the control of soilborne diseases. This chemical is not considered

to be as effective as a herbicide, nematicide, or insecticide as compared to methyl bromide

(Noling and Overman, 1988) (for a brief tabular review of information derived from the

specimen label for Chloropicrin, refer to Appendix Table D).







Non-Chemical Alternatives

Reduced Use of Methyl Bromide

In order to reduce emissions of methyl bromide into the atmosphere several alternatives

are being studied. One possible alternative could be reduction of the crop bed size: from 32 to

36 inches in width to 24 inches in width. The result is less chemical required to treat the bed

area. Preliminary studies have shown a 33% reduction in use of methyl bromide using this

method. Another alternative is to increase the amount of chloropicrin as a percent of the total

formulation so that less methyl bromide is used. Finally, the use of thicker or impermeable

plastics for bed covers can reduce the loss of methyl bromide by as much as 75%.


Constructed Barriers

Studies are currently in progress to evaluate the use of a barrier-type construction to

protect plants from nematodes. A sleeve inserted into the ground surrounding the plant can

provide a barrier against nematodes migrating into the root zone. However, a study examining

this method found that nematodes moved vertically into the rootzone from below, casting doubt

on its viability for controlling nematodes. Further research is being done using a V shaped

barrier to examine movement of nematodes into the root zone.


Crop Rotation

Crop rotation can be defined as "diversifying crops over time" and can be useful in

reducing the incidence of pests such as nematodes, pathogens and weeds. This method is

considered a viable alternative, depending on the pests and situation at the time of consideration.

For example, biological requirements of the pests and agronomic and economic implications may







dictate whether this is a feasible alternative (Flint and Roberts, 1988). The advantages of crop

rotation include improvement of soil texture, conservation of water, and improved weed control.

These advantages result because of rotation into crops with different cultural practices than those

practiced for the prior crop (Flint and Roberts, 1988).

In the state of Florida however, rotation to a selected crop in order to reduce populations

of certain pests may result in an increase in numbers of other pests such as nematodes and/or

fungi (Rhoades et al., 1966). Another disadvantage of this method is that it may take several

years of rotation to reduce populations to acceptable levels.


Hot Water or Steam

Byars and Gilbert (1920) found that heat treatment of potting soils or greenhouse soils

killed root knot nematodes and fungi such as Rhizoctonia and Pythium. A researchable

alternative to methyl bromide is an extension of that treatment whereby hot water treatment of

the field or injecting hot water into the soil via shanks is done to control some soilborne pests

such as nematodes. A machine has been developed that kills weeds and other potentially

dangerous pests by scalding. However, the machine is prohibitively expensive at the present

time (Ulrich, 1993).

Steam sterilization of potting or greenhouse soils has also been found to be effective and

is used extensively to treat medium used to grow transplants for vegetable production. The use

of steam sterilization for field application is considered cost prohibitive and dangerous for

workers involved. Cost of application can exceed $2500 per acre. This method is not

considered as effective against weeds and nematodes as methyl bromide.






Solarization

Solarization requires the trapping of heat under a transparent polyethylene tarp, to raise

soil temperatures high enough to prove lethal to plant pathogens and pests in the soil (Devay,

1991b). Soil solarization has been found to be effective in the control of nematodes (Lamberti

and Greco, 1991) and (Satour et al., 1991) weeds (Abu-Imailech, 1991), and fungi and bacteria

(Devay, 1991a). However, for effective control, this method is dependent on several factors,

such as temperature and moisture.

This method is most effective when practiced during the warmest part of the year, with

bright sunny days for 4 to 8 weeks raising soil temperatures to lethal levels for control of

nematodes (Heald, 1987). Soil moisture is important in this treatment for maximum heat

transfer to soilbore organisms and reduction of evaporative heat loss, providing a greenhouse

effect (Noling, 1992). Other factors that influence the effectiveness of solarization include air

temperature, length of day, sunlight intensity, and thickness and light transmittance of the plastic

being used (Devay, 1991b).

In Florida however, the hottest part of the year experiences cloud cover with heavy

rainfall. Thus, water collects on the surface of the plastic, resulting in heating the water instead

of the soil. Another problem with solarization as a non-chemical alternative to methyl bromide

use is that much of the soil is of the sandy type in vegetable producing regions of Florida.

These soils drain well and do not retain moisture, which is required for effective transfer of heat

to soilborne organisms (Noling, 1992). Soil solarization is ineffective in the control of nutsedge,

which is a major weed problem in certain regions of Florida. Other considerations when using

plastic for solarization are the longevity and disposal of the plastic. The integrity of the plastic







is broken down over time by ultraviolet radiation, and the cost to remove and dispose of plastic

can exceed $235 per acre (Noling, 1992). Soil solarization using clear plastic in conjunction

with a biological antagonist (such as an increased population of beneficial microorganisms to

reduce nematode populations) or a registered nematicide, may be an alternative for control of

soilborne pests such as nematodes.


Microwave

Research has been conducted to examine use of microwaves to sterilize the soil. At

10,000 watts it took 280 hours to treat 7,200 linear feet of 8 inches of soil. Soil has a

tremendous buffering capacity and soil moisture becomes a limiting factor when using this

method.


Soil Flooding

Flooding has been found to reduce populations of root knot nematode. Greenhouse tests

showed that one month of flooding, followed by one month of dry period, and finally one more

month of flooding, reduced numbers of root knot nematode (Rhoades et al., 1966). In Florida

however, current permitting requirements and limited water resources impede the use of this

practice.


Soil Amendments

The use of soil amendments is a means of biological control. For example, Rodriguez-

Kabana and Morgan-Jones (1987) examined the use of organic and inorganic materials that

release ammoniacal nitrogen that enables beneficial microorganisms to suppress populations of

nematodes. The release of nitrogen has been found to increase microorganisms that are







considered agnostic to nematodes. However, raising soil populations to desired levels often

resulted in phytotoxic symptoms in plants. Large amounts of nitrogen were required for

effective use of this treatment, and it proved to be cost prohibitive.

Kloepper et al. (1992) looked at the use of rhizobacteria to treat seeds. This study found

that rhizobacteria derived from the roots of antagonistic plants may be beneficial in reducing

populations of phytopathogenic nematodes. The use of soil amendments will require further

research before commercial application of this method could be considered.


Host Plant Resistance

Host plant resistance (HPR) is an alternative that enables the plant to grow and produce,

despite populations of pests. This method identifies genes that confer resistance to a given plant,

and once identified, is introduced into the desired plant. For example, the gene Mi was

identified for resistance to root knot nematode in the wild species of tomato. This gene was then

introduced into varieties of desirable cultivars of tomato (Fassuliotis, 1987). However, the

identified Mi gene is considered heat instable, therefore, in regions of warm temperatures the

resistance to root knot nematode is lost (Roberts, 1992). Genes for resistance have also been

identified for other crops such as sugar beet and beans (Fassuliotis, 1987). Once the gene has

been identified and introduced into the desired cultivar, however, another problem has been that

new virulent races or pathotypes occur, which can overcome the new resistant cultivar

(Fassuliotis, 1987). As these experiments suggest, host plant resistance for use in commercial

operations is limited due to problems associated with identification and transfer of genes to

desired cultivars (Roberts, 1992).








Fallow Land

Many soilborne pests can be controlled by depriving them of suitable plants upon which

to feed (Christie, 1959). However, allowing a parcel of land to remain fallow for a period of

time has several limitations. First, cost to growers may inhibit the option for land to remain

fallow. In addition, when allowing a field to be fallow, introduction of weedy species can

harbor pests and actually negatively affect the reduction of nematodes. Minton and Parker

(1987) found that nematodes were higher in the fallow plots, versus plots that were planted in

rye during the fallow period. It was suggested that weeds that took over the fallow plot may

have been a better host to the nematode than the plot in rye. It has also been found that clean

fallow, such as treatment of a field with herbicides to control weeds, can reduce root knot

nematode. However, this method is not recommended for Florida due to the loss of organic

matter, which may dry and erode (Rhoades et al., 1966). Use of chemicals to control weeds

is much slower in reducing populations of nematodes because the nematodes move deeper into

the soil, and are not subjected to adverse weather conditions (Noling, 1992).


Cover Crops

The use of cover crops has been found to reduce populations of soilbore pests, however

it is dependant on the type of cover crop used. For example, the use of clover was found to be

ineffective as a cover crop due to the inability of the plant to cover the field and inhibit the

growth of other species of weeds that may present a more suitable host.







SECTION 4

COMMODITY PRODUCTION AND PEST CONTROL PRACTICES


Watermelons

Approximately 45,000-60,000 acres of watermelon are planted annually in Florida,

making Florida the leading state in the production of watermelons. During the 1991-92 season,

approximately 53,000 acres were planted of which 45,000 acres were harvested (FASS, 1993).

Varieties grown in Florida include Charleston Gray, Charlee, Crimson Sweet, Jubilee,

Jubilee II, Mirage L.S., Prince Charles, Royal Jubilee and Sangria (Maynard, 1992).

Watermelon harvests begin in April or May progressing north and west and end in July. Some

watermelons are grown in the fall in south and central Florida (Stall and Showalter, No Date).

When practicing double cropping, watermelon is a good crop to follow crops such as

tomato or pepper. Watermelon is only grown on plastic as a second crop in South Florida,

otherwise it is grown on an open bed system with no plastic or methyl bromide. In North

Florida an estimated 3,000 acres of watermelon are grown on plastic as a first crop in order to

hit the early market window. Plastic mulch enables the grower to plant earlier in the season due

to the warming effect upon the soil when using mulch.


Cultural Practices

Watermelon production can occur on a variety of soil types, however, it is not

recommended to plant watermelon on muck soils. In order to improve the effectiveness of

herbicides and fumigants, it is suggested to plow under old crop residue for decomposition of

organic matter. The soil pH should be checked and adjusted as required (Maynard, 1992).







Disking the field can ease future activities, such as bed formation. In areas where standing

water is a problem, it is important to form beds, approximately 3 to 8 inches in height for

drainage. Several machines can shape the beds, such as disc hillers or a bedding disc. A bed

press can be used where plastic is installed. For watermelon production using plastic mulch,

chemicals and fertilizers applied to the soil should be applied prior to the application of the

mulch. The top of the beds should be approximately 20 to 24 inches across and covered with

plastic 48 inches wide (Maynard, 1992).

Watermelons can be planted by direct seed or by using transplants, however, bare root

transplants are not recommended. When using the direct seed method, it is important to place

several seeds together to ensure a good stand. Thinning of seedlings can be performed later.

If plastic mulch is used, direct seeding can be done using the plug-mix method using a plug-mix

planter. If transplants are used, containers or peat pellets should be used in order to maintain

an intact root system for successful transplant of watermelon. There are several machines that

are designed to install transplants (Maynard, 1992). Use of seeds is common, however, some

growers who grow hybrid watermelons on mulch are using transplants. Growers using hybrids

may be more inclined to grow watermelon on mulch.

Application of fertilizer becomes important depending on the method of production

system used including (1) non-mulched with overhead irrigation, (2) full-bed mulch with

overhead irrigation, (3) non-mulched with drip irrigation, and (4) open bed production with drip

irrigation. Fertilizer application methods vary according to the production system.

For non-mulched production with overhead irrigation, it is suggested that all phosphorous

(P), micronutrients, and 25 to 50 percent of required nitrogen (N) and potassium (K) be







incorporated into the bed prior to planting. The remaining N and K can be applied in two

sidedress applications approximately four to six weeks after emergence of seedlings. Any

additional requirements can be applied as needed. Full-bed mulch production with overhead

irrigation requires that all fertilizers are incorporated into the bed prior to application of mulch.

Any additional requirements of nitrogen (N) and potassium (K) can be added by the use of a

liquid fertilizer injection wheel. For watermelons grown as a non-mulched production system

with seepage irrigation, it is recommended to incorporate all of the phosphorus (P) and

micronutrients, and approximately 15 to 20 percent of the nitrogen (N) and potassium (K) into

the bed prior to planting. The application of the remaining N and K should be applied as a

sidedress band along the shoulders of the bed outside of the tips of the vines (Maynard, 1992).

For watermelons grown using drip irrigation, it is recommended to incorporate 20 to 40 percent

of nitrogen (N) and potassium (K) with all phosphorus (P) and micronutrients prior to planting.

Any additional requirements can be applied via the drip irrigation as needed. Insects are used

for pollination in the production of watermelon.


Diseases

Methyl bromide is used as a method of control for several diseases found in watermelon

production, such as damping-off and fusarium wilt.

Damping-off can be caused by Pythium, Fusarium and Rhizoctonia spp. This disease

affects watermelon seedlings, causing necrosis and death of the plant. The soilborne fungi can

invade the plant at or below the soil level.







Cultural practices recommended for control of damping-off include ensuring crop residue

is well turned under or decomposed, avoiding planting in soils that are cool, and using healthy

transplants. Use of treated seeds is also suggested.

Table 4.1 lists non-fumigant chemicals that can be used to control damping-off in

watermelon. Fumigant chemicals such as Vapam or Telone C-17 may also be effective in

control of this soilborne disease.



Table 4.1. Chemicals for the control of damping-off.

Common Name Trade Name

Metalaxyl 2 Subdue G

Metalaxyl 25 Subdue II

Metalaxyl 25.1 Ridomil 2E


NOTE: For rate, use, and application to seed bed and field, refer to pp. 468-469 of the Florida
Plant Disease Control Guide, 1993.



Fusarium wilt, caused by the fungus Fusarium oxysporum f.sp.niveum, infects the root

and stem of a watermelon plant. An overall wilting may result or individual runners may be

affected. Roots may become brown and a soft rot can sometimes develop near the crown

(Maynard, 1992).

Cultural practices used to control fusarium wilt include use of disease free transplants,

removal of or plowing in plant debris after harvest, rotation with a non-susceptible crop,







fumigation, delayed thinning and use of plant resistant varieties such as Charleston Gray,

Crimson Sweet, Dixielee, Jubilee, Sugarlee, and Sweet Princess. Even in resistant varieties,

infestation of the disease can still occur. It is also suggested to avoid old land that has been

planted with watermelon or to have known infestation of fusarium.

There are no chemicals listed for management of fusarium wilt. However, fumigant

chemicals such as Vapam or Telone C-17 may aid in the control of the soilborne disease.


Nematodes

Methyl bromide is used to control several nematodes that pose a threat to watermelon

production, including sting and root knot nematode. However, losses as a result of root knot

are not that common. This may be because plantings usually occur on acreages that have a long

rotation into pasture.

Cultural practices used to control nematodes include crop rotation which can.be used to

decrease populations of root knot nematodes in a given location. For example, corn, sorghum,

bahia grass, bermuda grass and pangola digit grass have been identified in reducing populations

of nematodes. It is also important to ensure complete removal or breakdown of the infested

crop. Cultivation can remove plants that harbor nematodes. Use of plants that are nematode

free and healthy is important in the battle with nematodes.

There are several non-fumigant and fumigant chemicals that are used for control of

nematodes including Vydate L, a non-fumigant, and Telone I or Telone C-17, a fumigant

chemical (for rate and application method, refer to pp. 96-97 of the Florida Nematode Control

Guide, 1993).








Weeds


Several methods have been identified to reduce weed populations including crop

competition, mechanical control, mulching, and use of chemicals. It is recommended to use

several of these methods in combination to obtain effective weed control. Disking, hoeing,

mowing, or cultivation can also be an effective method of weed control. Crop competition can

be a method of control by not only increasing the number of crop plants to effectively compete

against weeds for water and nutrients, but also ensuring a healthy crop population by using good

water and nutrient management practices. The use of plastic mulch in conjunction with fumigant

chemicals can be effective in the control of many weeds. The mulch itself acts as a barrier to

many weeds, with the exception of nutsedge which can grow through the plastic.

Methyl bromide is used as a method of control for weeds found in watermelon

production, such as crab grass, panicum, goosed grass, and lambsquarter. The following is a

list of other chemicals that can be used to control weeds. Bensulide (Prefar) is preplant

incorporated and used for control of germinating grasses. Bensulide + naptalam is applied

preplant or pre-emergence for a wide range of weed control. Diquat (Diquat) can be applied

post-emergence, for burdown of vines after final harvest. Sethoxydim (Poast) is used for post-

emergence control of grass weeds. Paraquat (Gramoxone) is used as a post-emergence contact

for control of all emerged weeds, and it is used in row middles between beds or as a pre-

emergence application. Ethalfluralin (Curbit) is applied pre-emergence & post-emergence, for

control of grasses such as goose grass, crabgrass, fall and Texas panicum, and broadleaf signal

grass. Glyphosate (Roundup) can be used prior to planting for removal of weeds for planting.

Naptalam (Alanap) is applied as a pre-emergence for control of germinating annuals such as







lambsquarter, pigweed, and carpet weed. For post transplant, it is recommended to apply this

chemical immediately after transplant for control of annual weeds. DCPA (Dacthal W-75) is

applied as an early post-emergence (for application rates and comments, refer to pp. 312-316

of the Florida Weed Control Guide, 1993).


Insects

Insects, such as wireworm, may increase in population with the removal of methyl

bromide in watermelon production. Methods of control of wireworm include Diazinon, a non-

fumigant, and Telone II or Telone C-17, a fumigant chemical (Florida Insect Control Guide,

1993).


Trends

Currently, central Florida watermelon growers do not use methyl bromide to any great

extent, due to the ability of growers to rent pasture land that has not been used for watermelon

production for several years. As the use of hybrids increases and availability of land becomes

limited, the practice of using methyl bromide could increase over the next few years.


Tomatoes

The primary areas of tomato production in Florida include Dade County, the East coast,

Palmetto/Ruskin area, Southwest Florida, and West, North and North-Central Florida. Acreage

in production in Florida has varied between 41,000 and 62,000 acres over the last decade.

During the 1991-92 season total state production was estimated at 51,300 acres. Acres planted

by production area are shown in table 4.2. There are many varieties of tomatoes grown in

Florida. Sunny is the leading variety with 51.7% of acreage for the 1991-92 season, followed

40







by Solarset (10.5%), Agriset (9.8%), and Bonita (7.8%). BHN 90, Olympia, Heatwave and

Colonial are used on most of the remaining acreage in production (FASS, 1993).



Table 4.2. Acres of tomatoes planted in Florida by production area for the 1991-92 season.

Production Area Acres

Dade County 5,100

East Coast 6,000

Palmetto/Ruskin 15,400

Southwest Florida 21,200

West, North and North-Central 3,600

Source: FASS, 1993.



Cultural Practices

A field should be plowed and disked to turn under old crop residue in order to reduce

detrimental soil organisms. The soil should be analyzed for any additional additives required,

such as lime for pH adjustment. Then the bed is shaped, fumigated, and fertilized using a bed

disk. If plastic is to be applied, then a bed press is used to apply plastic following the bed disk.

Black plastic is normally used, however, during the early fall when temperatures can still be

relatively warm, growers may use black with a white band over the middle region, gray, or

white to reduce the temperature of the surface of the bed. Some advantages of plastic







include increased weed control, moisture retention, and reduced loss to leaching of fertilizer

(Hochmuth, 1988a).

There are several types of bedding production systems in Florida including (1) non-

mulched tomato, (2) strip mulched tomato, (3) full-bed mulch with seep irrigation, (4) full-bed

mulch with overhead irrigation, or (5) full-bed mulch with drip irrigation.

In non-mulched tomato production, fertilizer is incorporated into the soil and then a band

or strip four to five inches wide of nitrogen (N) and potassium (K) are incorporated along the

edge of the bed. Subsurface or overhead irrigation can be used for application of water.

In strip mulched tomato production, all micronutrients are incorporated into the soil along

with 20% of nitrogen (N) and potassium (K). A band of fertilizer is placed two to three inches

below the surface of the plastic. The strip of plastic is ten to twelve inches wide and is placed

in the center of the bed with tomatoes growing through the hole in the plastic. Overhead or

subsurface irrigation can be used for application of water.

In full-bed mulch systems with seep irrigation, all soil requirements such as fumigants

and fertilizers are added prior to the application of plastics. Any additional application of

fertilizers can be done using an injection wheel. The following is a sequence of operations that

may be used in a full-bed mulch system with seep irrigation. First, land preparation includes

installation of irrigation, drainage system, and pH adjustment. Second, application of fertilizers

includes total micronutrients with phosphorus (P) incorporated along with 10-15% of nitrogen

(N) and potassium (K) added to the soil. Third, formation of bed includes application of mole

cricket bait and herbicides for weed control. Fourth, the remaining fertilizer is applied in a nine

to ten inch band on either side at one to two inches in depth. This step also includes fumigation,






pressing of beds, and application of plastic mulch. To prevent escaping fumes of fumigant, the

edges of the plastic are covered with soil to seal the edges (Hochmuth, 1988a). Fifth, water is

maintained approximately fifteen to eighteen inches below the soil surface to ensure seepage into

the root zone and to maintain moisture. By maintaining a moist environment, a nutritional

concentration gradient exists. This allows the banded nitrogen (N) and potassium (K) to diffuse

into the soil and replace those nutrients already incorporated into the soil. Plastic is extremely

important in maintaining soil moisture, otherwise the nutrients can be lost to leaching by natural

rain, or the soil may dry out and result in evaporative loss of soil moisture (Geraldson, No

Date).

Mulched tomato production with overhead irrigation is similar to a full-bed mulch system

with seep irrigation with the following exceptions. In sandy soils all fertilizers are incorporated

into the soil. In areas with a soluble salt problem, a percentage of fertilizer is incorporated into

the soil and any remaining fertilizer is added as required. Perforated plastic is not required,

since the water that is applied, soaks in at the hole in the plastic and is sufficient to supply plant

needs. Some methods of overhead irrigation include the use of travelling guns, solid set

sprinklers, or center pivot systems. One disadvantage of overhead irrigation is the threat of the

spread of foliar diseases due to increased moisture on the leaves. In rockdale soils perforated

plastics are required due to minimal lateral water movement in the soil. Placement of

superphosphate close to the transplant is also required for uptake because phosphate is considered

immobile in the soil.

A mulched tomato production system with drip irrigation is similar to a full-bed mulch

system with seep irrigation with the exception of the following. Drip irrigation is accomplished






either by tubes or drip tape which is placed approximately four to five inches below the soil

surface prior to the application of plastic. Placement below the soil surface protects the tape

against mice and cricket damage. Drip irrigation enables the grower to apply fertilizer via

irrigation. Total phosphorus (P) and micronutrients, and 20-40% of total nitrogen (N) and

potassium (K) are applied prior to mulch application and planting. The remaining N, K, and

other nutrients required during the life cycle of the plant can be injected using the irrigation

system (Hochmuth, 1988a).


Planting Techniques. There are three techniques that are normally used in planting

tomatoes: direct planting of the seed, bare root transplants or containerized transplants. The

primary method practiced on rockdale soils in Dade County is direct planting of the seed through

the plastic mulch using a plug mix method. This method requires tomato seed, fertilizer, and

water to be mixed with vermiculite and peat. This mixture is allowed to sit for 12 to 48 hours

and enables the seed to imbibe (absorb or to take up) water, thus beginning the germination

process. This mixture is then placed in the field by a plug mix planter machine. When placed

in the field, a machine either burs or cuts a hole in the plastic, then inserts the plug mixture

in the soil. There are usually several seeds per plug, requiring labor to weed out the undesirable

plants after they have grown a few inches. In a bare root transplant method, plants are grown

in fumigated soils with a pH range of 6.0 to 6.5. Once the seedlings have reached a height of

five inches, they are ready to transplant. The transplant soil must be moist when transplanting

for ease of removal, however the soil must not be soaked due to enhanced environment for

detrimental organisms to enter the transplants. Containerized transplants are grown in a multi-

cell or tray pack system. Trays can be styrofoam or plastic, and they must be sterilized prior







to installation of seeds. Transplants are usually raised in a greenhouse to optimize growing

conditions (Hochmuth, 1988a). A large percentage of tomato growers purchase their transplants

for installation.


Staking. Stakes are approximately forty-eight inches in length and are placed in the

ground within the row when plants are approximately two to three weeks old. Plastic twine is

used to tie the plant to the stake and is usually done three to four times during the growth of the

plant. Plastic twine is used due to the ease of removal by burning. Once the final harvest is

complete, plants are killed with herbicides (usually Paraquat which is a quick reacting contact

spray), and then the plastic is slit down the middle and lifted out of the soil (unless a second

crop is planted to re-use the plastic). Stakes can be removed by a stake puller and sterilized by

either steam or methyl bromide (Hochmuth, 1988a). When sterilizing stakes with methyl

bromide, the stakes must first be moistened, then a tarp is placed over the entire stack and

fumigated. This method is usually only done in areas of high fungal disease activity,

however this is not a common practice. Another method used to sterilize stakes is placing

stakes in a barrel containing a solution of clorox and water (Stall, 1993).


Diseases

Methyl bromide is used as a method of control for several diseases found in tomato

production including fusarium crown and root rot, bacterial wilt, southern blight, and

verticillium wilt.

Fusarium crown and root rot (Fusarium oxysporum f. sp. radius lycopersici (FORL))

is a fungus which is severe in southern production regions of Florida. FORL invades the plant







through wounds and natural openings such as new root shoots. Symptoms occur as brown

lesions which can girdle the hypocotyl at the root/shoot juncture. In tomato seedlings the fungus

can cause yellowing, stunting, and loss of cotyledons (source of food). Field symptoms are

exhibited by wilting of the plant during the warmest part of the day but the plant may recover

during the evening hours. As the plant begins to bear fruit the increased stress may cause

symptoms to become more prominent. Some plants may produce irregular fruit and in some

situations may lead to death (McGovern and Datnoff, 1992).

Cultural practices used to control FORL include using disease free transplants, avoiding

over-watering, and using mixed tray types such as plastic or styrofoam due to different watering

requirements. Trays should be disinfected prior to reuse. Avoid injury to transplants or later

stages of plant development because wounds provide an entry point for a pathogen. Maintain

optimum soil pH between 6-7 and do not drag trays along the ground because the trays can pick-

up spores and spread disease. Remove or plow in plant debris after harvest to reduce

populations of soil pathogens and sterilize stakes prior to re-use. Rotate with a non-susceptible

crop, such as a monocot type of plant like corn (McGovern and Datnoff, 1992).

The use of a biological control which increases the populations of microorganisms such

as Trichoderma harzianum, Aspergillus ochraceus Glomus intraradix, orPenicillium funiculosum

can effectively decrease the populations of FORL in the soil (McGovern and Datnoff, 1992).

Heating the soil by the use of transparent plastics in conjunction with biological control

may be a viable alternative in the control Fusarium crown rot (McGovern and Datnoff, 1992).

Chemical controls are another method of management of Fusarium Crown and root rot. Soil

fumigants such as methyl bromide mixed in varying concentrations with chloropicrin, have been







found to be effective in the control of FORL (McGovern and Datnoff, 1992). Other chemicals

include formulations containing methylisothiocyanate.

Bacterial wilt is caused by Pseudomonas solanacearum and expresses symptoms such as

dark discoloration near ground level. The plant appears to be stunted before signs of wilting and

yellowing appear. Cultural practices for control of bacterial wilt include fumigation of land

prior to installation of seedbeds or field planting. In order to reduce the spread of disease, it

is recommended to avoid flooded conditions and avoid movement of tractors from infested fields

to non-infested fields. It is also recommended not to plant in fields that have a history of disease

problems.

Table 4.3 contains a list of chemicals that can be used to control bacterial wilt. The

principal chemicals are chloropicrin, methyl bromide, and Vapam.



Table 4.3. Chemicals for the control of bacterial wilt.


Common Name Trade Name
Chloropicrin 96.5 Chlor-O-pic/Picfume
Methyl Bromide 68 Brom-O-Sol/Brozone
Methyl Bromide + Chloropicrin 67:32 MC-33/Terr-O-Gas 67
Metam Sodium 32.7 Vapam/Fume V

NOTE: For rate, use, and application to seed bed and field, refer to pp. 440-461 of the Florida
Plant Disease Control Guide, 1993.



Southern blight is caused by Sclerotium rolfsii and attacks the plant at or below ground

level by completely girdling the plant. This prevents movement of water or nutrients through







the plant thereby limiting support to the upper portion of the plant. As a result the plant wilts

and eventually dies. Young plants such as seedlings are especially susceptible, but as the plant

becomes more woody, it becomes more resistant to attack (Florida Plant Disease Control Guide,

1993).

If a field inspection reveals plants infected with southern blight, the plants should be

removed and disposed of by burying or burning. It is recommended to avoid excess water in

the field by following proper irrigation and drainage practices. Flooding can lead to spreading

of the disease by dissemination of sclerotia, however they are too heavy to spread by

atmospheric means such as wind. It is also recommended to plow under crop residue at least

6 inches in depth to reduce increases in populations of soil pathogens (Florida Plant Disease

Control Guide, 1993).

In Table 4.4 a list of chemicals that can be used to control southern blight is presented.



Table 4.4. Chemicals for the control of southern blight.

Common Name Trade Name
Chloropicrin 96.5 Chlor-O-pic/Picfume
Methyl Bromide 68 Brom-O-Sol/Brozone
Methyl Bromide + Chloropicrin 67:32 MC-33/Terr-O-Gas 67
Metam Sodium 32.7 Vapam/Fume V
PCNB 75 Terraclor 75WP

NOTE: For rate, use, and application to seed bed and field, refer to pp. 440-461 of the Florida
Plant Disease Control Guide, 1993.






Verticillium wilt, caused by Verticillium albo-atrum, does not kill the plant, however,

it does disable the plant where it can no longer effectively take up nutrients. Symptoms do not

become apparent until fruit set. Symptoms consist of diurnal wilting, where the plant regains

turgor during the evening hours, and marginal yellowing.of the leaves (Florida Plant Disease

Control Guide, 1993).

Cultural practices for management of verticillium wilt include use of resistant or tolerant

varieties. It is recommended to rotate the crop with a non-susceptible crop and avoid

overwatering. It is also recommended to not plant on land with a known history of Verticillium

wilt and to practice sanitation methods, including removal or plowing under of plant debris after

harvest and disinfecting stakes used during crop production. (Florida Plant Disease Control

Guide, 1993).

Table 4.5 contains a list of chemicals that can be used to control Verticillium wilt. The

principal chemicals are chloropicrin, methyl bromide, and Vapam.



Table 4.5. Chemicals for the control of verticillium wilt.

Common Name Trade Name
Chloropicrin 96.5 Chlor-O-pic/Picfume
Methyl Bromide 68 Brom-O-Sol/Brozone
Methyl Bromide + Chloropicrin 67:32 MC-33/Terr-O-Gas 67
Metam Sodium 32.7 Vapam/Fume V

NOTE: For rate, use, and application to seed bed and field, refer to pp 440-461 of the Florida
Plant Disease Control Guide, 1993.







Nematodes

There are several nematodes that pose a constant threat to Florida tomato production.

The most common are: root knot nematode, which is found in sand, muck, and rock base soils;

stubby-root nematode, which is found in sand and muck soils and; sting nematode, which is

found in sand soils.

There are several fumigant and non-fumigant chemicals that are used for control of

nematodes. Nemacur and Vydate are two non-fumigant nematicides which are not as effective

against root knot nematode as are fumigant type chemicals. Fumigant nematicides include

methyl bromide plus chloropicrin (varied ratios), Vapam, Busan 1020, and Telone II and Telone

C-17. (Florida Nematode Control Guide, 1993).


Weeds

Some common weeds found in tomato production in Florida are nightshade, eclipta alba,

goosegrass, southern crabgrass, bermudagrass, yellow nutsedge, pigweed, morning glory,

carolina geranium, ragweed, and parthenium. Methods of weed control include mechanical

weed control, crop competition, crop rotation, biological weed control, and chemical use. To

obtain effective weed control it is suggested to use two or more of these methods in

combination.

Mechanical weed control includes turning weeds under by cultivation, however several

studies have shown that this process germinates more weeds by disturbing the seeds that lie

below the surface. Crop competition increases the number of crop plants to effectively compete

against weeds for water and nutrients. Crop rotation helps control weeds because monocropping

year after year results in build up of weeds that are tolerant to monocropping cultivation








practices. Biological weed control includes introduction of an organism to reduce the population

of undesirable pests.

Chemical weed control includes use of herbicides and fumigants to control weeds. Non-

fumigant chemicals include: DCPA (Dacthal) which controls germinating annuals; Diquat which,

via contact, burs down vines after final harvest; MCDS (Enquik) which is a post-emergence

control of broadleaf weeds; Metribuzin (Sencor) which controls post-emergence of small weeds;

Napropamid (Devrinol) which is a preplant incorporated-control for germinating annuals (applied

before plastic application); Paraquat (Gramoxone) for post-emergence contact-control for all

emerged weeds (used in row middles between beds); Sethoxydim (Poast) for post-emergence

control of grass weeds; and Trifluralin (Treflan) applied preplant for control of germinating

annual weeds (for application rate and comments, refer to pp. 339-342 of the Florida Weed

Control Guide, 1993). Fumigant chemicals used to control weeds include methyl bromide and

Vapam.


Insects

Insects, such as wireworm, may increase in population with removal of methyl bromide

in tomato production. Methods of control for wireworm include Diazinon, a non-fumigant

chemical, and Telone and methyl bromide which are fumigants (for application rates and

comments refer to the Florida Insect Control Guide, 1993, p. 542).


Strawberries

Approximately 3,000 to 5,500 acres of strawberries are planted annually in Florida. For

the 1991-92 season, 4,700 acres of strawberries were harvested in Florida. Hillsborough and








Manatee counties produce the majority of the strawberries, harvesting approximately 4,200 acres

in 1991-92. The value of this crop in Florida was estimated at more than $94 million for the

1991-92 season (FASS, 1993). Some of the varieties grown include Oso Grandy, the most

popular, followed by Selva, Sweet Charlie (a Florida variety), and Seascape. Transplants are

set in October and harvest generally begins in December, peaking in March and early April with

some late harvest into May (Albregts and Howard, 1984). Some double cropping does occur

using vegetables such as pepper, eggplant, or squash, however this is not considered a common

practice. Some growers use cover crops to build up organic matter and return some of the

nutrients to the soil and to reduce infestation of weeds during the fallow period.


Cultural Practices

The primary production method in strawberry farming is a full-bed mulch system using

overhead irrigation in conjunction with seepage or drip irrigation. Farmers sometimes use

recycled water collected in pits for irrigation.

The field should be plowed prior to planting and disked to turn under old crop residue

in order to reduce detrimental soil organisms. The field should then be leveled for proper

drainage to prevent areas of flooding. The soil should be analyzed for any additional additives

required, such as lime or sulfur for pH adjustment (Kostewicz, 1976).

Strawberries are grown on beds to reduce flood damage to the crop. The height of the

bed ranges from 7 to 9 inches depending on the amount of drainage that is required (Hochmuth,

1988c). Beds are fumigated using a soil fumigant chemical such as methyl bromide.

Application of fertilizer requires that total micronutrients and phosphorous (P) are

incorporated into the bed with a percentage of nitrogen (N) and potassium (K) also added. The








remaining N and K can be banded along the outside edge of the row. The application of black

ethylene plastic is commonly used and is important for cultural reasons, such as weed control,

reducing erosion, and leaching of nutrients (Hochmuth, 1988c).

Field preparations such as bed shaping, fertilizing, and fumigation are gradually done in

one step, followed by the application of plastic in a separate operation. Generally, row bedding

ranges from two to four rows of strawberries per bed. When using two rows per bed, spacing

between plants is approximately 12 inches, however, as growers increase the number of rows

per bed, they will increase the spacing between plants to compensate for decreased row spacing

(Albregts and Howard, 1984).

The use of overhead sprinklers is common practice and is required to establish

transplants. Overhead irrigation is used for several days after setting transplants to reduce heat

stress damage to the plants. Overhead irrigation is also important for cold protection. This

method allows the grower to apply water over the plant. The actual phase change from liquid

to ice releases heat that is absorbed by the plant for protection against cold temperatures

(Albregts and Howard, 1984).

Strawberry plants can be classified as either dormant or non-dormant. Those plants that

have not been exposed to temperatures below 45F are non-dormant, meaning there has been

little accumulation of starch in the roots for vegetative development. Strawberry plants classified

as dormant have received a number of hours below 45F and have accumulated a sufficient

amount of starch in the roots to supply food for vegetative growth. Most growers purchase their

transplants from nurseries located in the northern regions of the U.S. or Canada. These plants

can accumulate the required amount of hours below 45*F in order to sustain itself once







transplanted to the field. The plants received from nurseries in the north are partially dormant

because it is important to have a plant with enough starch in the roots to establish itself in the

field, and then begin flowering. If the plants receive too many hours below 45*F, resulting in

total dormancy, vegetative growth would be enhanced for several months and little flowering

would occur (Albregts and Howard, 1984).


Diseases

Methyl bromide is used as a method of control for several diseases found in strawberry

production including black root, Rhizoctonia bud rot, Rhizoctonia hard brown rot and

Verticillium wilt.

Black root is a complex of organisms which causes stunting of plants, blackening, and

decay of roots as a result of lack of oxygen in the soil (Hochmuth, 1988c). Cultural practices

recommended for control of black root include digging around the plants in the nursery which

provides soil aeration and aids in new root development. In Table 4.6, the chemicals that can

be used to control black root are listed. The principal chemicals are chloropicrin, methyl

bromide, and Vapam.








Table 4.6. Chemicals for the control of black root, rhizoctonia, and verticillium wilt.

Common Name Trade Name

Chlor-O-Picrin 96.5 Chlor-O-Pic, Picfume

Methyl bromide 98-100 Brom-O-Gas, MC-2R,

Terr-O-Gas 98 or 100

Methyl bromide 68 Brom-O-Sol, Brozone

Methyl bromide + MC-33, Terr-O-Gas 67
Chloropicrin 67:32

Metam sodium (SMDC) Vapam

Source: Florida Plant Disease Control Guide, 1993, pp. 426-427.



Rhizoctonia bud rot, caused by Rhizoctonia solani, attacks the bud portion of the plant

and can lead to death of lateral buds and sometimes the entire plant. Appropriate planting depth

is an important cultural management technique because the chances for infection increase if the

plant is planted too deep. In addition, avoid planting in areas where known species exists, and

allow the cover crop to dry prior to turning it under by cultivation. Cool weather and humid

weather are conducive environmental conditions for plant infection. Chemical controls include

the use of Benomyl or Thiram which can be used to aid control of foliar diseases caused by

Rhizoctonia species. In Table 4.6, the additional chemicals that can be used for preventive

control of Rhizoctonia caused diseases are listed.






Rhizoctonia hard brown rot, caused by Rhizoctonia solani, can affect the fruit, however

affected areas can be removed, and the fruit is still edible. Cultural practices for control of

Rhizoctonia hard brown rot include the use of mulch which reduces contact of the plant with the

soil. Chemical management of the disease includes the use of Benomyl or Thiram, which can

be used to aid in the control of diseases caused by Rhizoctonia species. Table 4.6 lists

chemicals that can be used for preventive control of Rhizoctonia caused diseases.

Verticillium wilt, caused by Verticillium albo-atrum, exhibits symptoms such as mature

leaves with inter-veinal browning which can cause eventual death of the tissue. This disease is

prevalent in calcareous soils in south Florida, however, it is not as common in central Florida

(Hochmuth, 1988c). Cultural practices to control verticillium wilt include the use of resistant

or tolerant varieties, however, these varieties are not currently available in Florida. It is

important to avoid injury to transplants and avoid installation of infected plants (Florida Plant

Disease Control Guide, 1993). It also is recommended to remove or plow in plant debris after

harvest of previous crops (Albregts and Howard, 1984). Table 4.6 lists chemicals that can be

used to control verticillium wilt. The principal chemicals are chloropicrin, methyl bromide, and

Vapam.

Nematodes

There are several nematodes that pose a constant threat to Florida strawberry production,

with the most common being sting and root knot nematode followed by bud and leaf nematode

(Hochmuth, 1988c).

Cultural practices for control of nematodes include the use of non-host cover crops. It

is also recommended to allow crop debris to completely decay prior to installation of new







strawberry plants (Hochmuth, 1988c). Telone II is a nematicide that is registered for use in

strawberry production (for rate and application method, refer the Florida Nematode Control

Guide, 1993, p. 110).


Weeds

Some common weeds found in strawberry production include nutsedge, indigo, carolina

geranium, and cutleaf evening primrose. Several cultural practices have been identified to

reduce weed populations including crop competition, mechanical control, crop rotation, cover

crops, and use of chemicals. To obtain effective weed control, it is suggested to use two or

more of these methods in combination.

Mechanical control of weeds includes turning the weeds under by cultivation using a disk

or by hoeing. Mechanical control of weeds also includes mowing. Crop competition increases

the number of plants to effectively compete against weeds for water and nutrients. Mono-

cropping year after year can result in the build up of weeds that are tolerant to cultivation

practices. Crop rotation can reduce the population of weed species specific to strawberry

production practices. The use of a cover crop during the off season can reduce populations of

undesirable weeds. Herbicides and fumigants can also be beneficial in controlling weeds.

The following chemicals can be used to control weeds in strawberry production. DCPA

(Dacthal) controls germinating annuals. MCDS (Enquik) is applied post-emergence to row

middles for control of broadleaf weeds. Napropamid (Devrinol), a preplant incorporate, can be

used to control germinating annuals. It is also applied before plastic application or as a surface

application. Sethoxydim (Poast) is applied post-emergence for control of grass weeds. Paraquat

(Gramoxone) is a post-emergence contact used for control of all emerged weeds. It can be used







in row middles between beds or as a pre-emergence application (for application rate and

comments, refer to the Florida Weed Control Guide, 1993). Methyl bromide plus varying

concentrations of chloropicrin can be used for preplant treatment of beds. The formulation of

98 percent methyl bromide and 2 percent chloropicrin is primarily used due to effective control

of nutsedge.


Insects

Insects such as wireworm may increase in populations with removal of methyl bromide

in strawberry production. Alternative methods of control for wireworm include non-fumigant

chemicals such as Lorsban, Dyfonate and Diazinon. Telone is a fumigant chemical used to

control wireworm (Florida Insect Control Guide, 1993).


Peppers

Peppers are considered a warm season crop with approximately 33% of United States

production occurring in the state of Florida (Gull, No Date). Approximately 20,000 to 23,000

acres of peppers are planted annually in Florida. For the 1991-92 season 20,600 acres of

pepper, valued at $170.8 million, were harvested. The leading counties for harvested acreage

included Collier (with 4,500 acres in 1991-92) and Palm Beach (with 5,500 acres in 1991-92)

(FASS, 1993). Florida produces peppers for the early and late-season, while Georgia and South

Carolina produce peppers for mid-season demand. Due to its physical characteristics, California

Wonder is the primary variety grown in Florida. Commercial users, such as restaurants, prefer

this blocky, four-lobed pepper because sliced in half, it remains stable when placed on a plate,








as compared to the three lobed pepper. Other varieties include Early Calwonder, Gator Bell,

Jupiter and Shamrock (Hochmuth, 1988b).


Cultural Practices

Double cropping is practiced in pepper production in order to use plastics or residual

fertilizers and chemicals. In west Palm Beach County double cropping may include an onion

or bean crop. When double cropping with beans, planters seed beans into the bed between the

pepper holes. When double cropping with onions, onion transplants are installed by hand. In

the Immokalee area, squash and cucumber have been used as a double crop with pepper.

The cultural practices for pepper production are very similar to tomato production. The

primary production method for pepper in the Palm Beach area is a full-bed mulch system with

seepage irrigation. Full-bed mulch production with seep irrigation requires that all soil

additives, such as fumigants and fertilizers, be added prior to the application of plastics. The

following is a sequence of operations that may be used in full-bed mulch production with seep

irrigation. First, the field should be plowed and disked to turn under old crop residue in order

to reduce detrimental soil organisms. Second, leveling of the field is required for proper

drainage and irrigation. Third, the soil should be analyzed for any additional additives required,

such as lime or sulfur for pH adjustment. Fourth, initial fertilizer application should be

completed, including all micronutrient and phosphorous (P) requirements and 10 to 15 percent

of total nitrogen (N) and potassium (K) requirements. Additional amounts can be applied

through an injection wheel as needed (Hochmuth, 1988b). Fifth, bedding (shape the bed),

fumigation, and application of fertilizer are done prior to the application of plastic. Advantages

of plastic include increased weed control, moisture retention, and reduced loss to leaching of







fertilizer. Black plastic with a painted white strip down the middle may be used during early

fall plantings. The white reflects the sun, creating cooler surface temperatures and reducing the

incidence of plant burning when portions of the plant come in contact with the plastic.

It is important to maintain water approximately 15 to 18 inches below the soil surface

to ensure seepage into the root zone and sustain moisture. By maintaining a moist environment,

a nutritional concentration gradient exists. This allows the banded nitrogen (N) and potassium

(K) to diffuse into the soil and replace those nutrients already incorporated into the soil. Plastic

is extremely important in sustaining the moisture, otherwise the nutrients can be lost to leaching

by natural rain or the soil may dry out and result in evaporative loss of soil moisture (Geraldson,

et al., 1965). Seepage irrigation can be an effective tool to limit root growth to the treated soil

in the bed area. By raising the water table, the growth of the root is restricted to the bed region.

Mulched production of peppers using the drip system is similar to full-bed mulch with

seep irrigation with the exception that water requirements are met by the use of drip irrigation.

Drip irrigation can be supplied either by tubes or drip tape which should be placed

approximately two to three inches below the soil surface prior to the application of plastic to

protect against damage incurred from mice and insects. Initial fertilizer application should be

comprised of all micronutrients and phosphorous (P) with 20 to 40 percent of total nitrogen (N)

and potassium (K) requirements. Additional N and K can be injected into the system during the

growth of the plant.

Pepper plants can be established either by transplants or direct seeding. Transplants can

be grown in a greenhouse nursery or in the field using fungicide treated seeds planted in

fumigated areas. The transplants then may be placed in the field by machine (Hochmuth,







1988b). Direct seeding using the "plug mix" method is considered most effective. The "plug

mix" is a mixture of seed, water, and soil placed in the ground by a planter machine. The

planter can be used for both mulched and nonmulched bed type production systems (Rose,

1974).

The bed shapes are similar in size and contour as is found in eggplant and tomato

production, however two or three rows of peppers may be grown on one bed. Stakes are usually

placed every two or three plants and are one-half the length of those used for tomato production.

Baling twine is used to wrap stake-to-stake to provide a support for pepper plants between the

stakes. Clorox and water can be used to sterilize stakes when required, however usually after

use and prior to storage, removal of dirt from stakes has been found to be adequate for control

of harboring pests that may remain on the stakes. Once the final harvest is complete, plants are

killed with herbicides, such as Paraquat or Roundup. Mowing may be used to remove excess

plant debris. A machine may then be used to pull up plastics and roll it into bales for disposal.


Diseases

Methyl bromide is used as a method of control for several diseases found in pepper

production such as damping-off and southern blight.

Damping-offcan be caused by Pythium sp. and Rhizoctonia sp. Symptoms are exhibited

by rotting at or below the ground level leading to the death of the seedling. Cultural practices

used to control damping-off include planting in well drained soils and planting in areas

containing reduced amount of decomposed plant debris. The use of fungicide treated seed can

also be an effective method of control. Table 4.7 lists chemicals that can be used to control

damping-off.






Table 4.7. Chemicals for the control of damping-off.

Common Name Trade Name

Chloropicrin 96.5 Chlor-O-Pic\Picfume

Methyl bromide 98\100 Brom-O-Gas\MC-2R

Methyl bromide 68 Brom-O-Gas\Brozone

Methyl bromide 67:32 MC-33, Terr-o-gas 67

Metam sodium Vapam

Metalaxyl 25 Subdue II

Metalaxyl 25.1 Ridomil 2E


NOTE: For rate, use, and application to seed bed and field, refer to pp. 390-393 of the Florida
Plant Disease Control Guide, 1993.


Southern blight, caused by Sclerotium rolfsi, attacks the plant at or below ground level

by completely girdling the plant, preventing water and nutrient movement to support the upper

portion of the plant. As a result, the plant wilts and eventually dies (Florida Plant Disease

Control Guide, 1993, p. 395). Cultural practices used to control southern blight include plowing

under all crop debris and ceasing to plant in areas with a known history of disease. Another

alternative is to rotate with a grass crop in fields with high populations of the disease (Florida

Plant Disease Control Guide, 1993, p. 395). Treatment of soil with multipurpose fumigants

such as Vapam or methyl bromide containing varying concentrations of chloropicrin also aids

in the control of the disease, if disease is present at the time of treatment.

62







Nematodes

There are several nematodes that pose a constant threat to Florida pepper production.

The most common are: (a) root knot nematode which is found in sand, muck, and rock base

soils; (b) stubby-root nematode found in sand and muck soils, and; (c) sting nematode found in

sand soils.

There are several fumigant and non-fumigant chemicals that are used for control of

nematodes. Vydate and Nemacur are two non-fumigant nematicides which are not as effective

against root knot nematode as fumigant type chemicals. Fumigant nematicides include methyl

bromide plus chloropicrin (varied ratios), Vapam, Busan 1020, and Telon II and Telon C-17

(Florida Nematode Control Guide, 1993, p. 11-115).


Weeds

The most common weeds found in pepper production are similar to those found in tomato

or eggplant production in Florida. These include nightshade, eclipta alba, goosegrass, southern

crabgrass, bermuda grass, yellow nutsedge, pigweed, dodder and morning glory. To reduce

weed populations, several methods have been identified including cover crops, mechanical

controls and use of chemicals. To obtain effective weed control, it is suggested to use two or

more of these methods in combination (Florida Weed Control Guide, 1993, p. 325).

Mechanical control can include turning the weeds under by disking. Cover crops can

help control problem weeds during the off season, however, the type of cover crop chosen

should not harbor pests or diseases that are detrimental to the pepper plant (Florida Weed

Control Guide, 1993, p. 325).







The use of herbicides and fumigants can also help in weed control. The following is a

list of non-fumigant chemicals that can be used to control weeds. DCPA (Dacthal) is used to

control germinating annuals. MCDS (Enquik) can be used for post-emergence control of

broadleaf weeds in row middles. Napropamid (Devrinol) is used preplant for control of

germinating annuals and should be applied before plastic application, or as a surface application.

Paraquat (Gramoxone) is applied post-emergence, as a contact chemical for control of all

emerged weeds, and can be used in row-middles (between beds), or as a pre-emergence

application. Sethoxydim (Poast) is used for post-emergence control of grass weeds. Trifluralin

(Treflan) is incorporated pretransplant and controls annual weeds. Diquat (Diquat) can be used

for burn down of crop after final harvest. Clomozone (Command) is applied preplant for control

of annual grasses and certain broadleaf weeds (Florida Weed Control Guide, 1993). The use

of fumigant chemicals such as methyl bromide or Vapam also reduces populations of certain

weeds.


Insects

Insects such as wireworm may increase in population with the removal of methyl bromide

in pepper production. Methods of control for wireworm include non-fumigant chemicals such

as Diazinon and Fonofos. Telone can work as a fumigant type of control (Florida Insect Control

Guide, 1993, p. 491).


Eggplant

Florida represents 51% of the commercially grown eggplant produced in the United

States (Gull, no date). Approximately 2,000 to 3,000 acres of eggplant are planted annually.








For the 1991-92 season, 2,550 acres of eggplant were harvested in Florida, with a cash value

of $16.9 million. Palm Beach County (East) harvested the most eggplant with 1,050 acres. The

remaining acres of eggplant for the 1991-92 season were harvested from various other counties

(FASS, 1993). The major type of eggplant grown in the Palm Beach area is the Classic variety

(Shuler, 1993). Other varieties include Florida Market and Florida Beauty (Hart, no date).

Eggplant production can generally occur year round. The vegetable crop that follows

eggplant in a double cropping production system depends upon prevailing environmental and

economic factors. Pepper or cucumber are the preferred vegetables when double cropping with

eggplant. Double cropping eggplant is not considered a common practice in Palm Beach

County.


Cultural Practice

The cultural practices for eggplant production are very similar to tomato production. The

primary production method for eggplant in the Palm Beach area is the full-bed mulch system

with seepage irrigation. This system requires that all soil additives, such as fumigants and

fertilizers, be added prior to application of plastics. The field should be plowed and disked to

turn under old crop residue in order to reduce detrimental soil organisms. The soil should be

analyzed for any additional additives required, such as lime or sulfur for pH adjustment

(Kostewicz, 1976). Then bedding (shaping the bed), fumigating, and fertilizing are done prior

to the application of plastic. Advantages of plastic include increased weed control, moisture

retention, and reduced leaching of fertilizer (Hochmuth, 1988a).

It is important to maintain water approximately 15 to 18 inches below soil surface to

ensure seepage into the root zone and sustain moisture. By maintaining a moist environment,






a nutritional concentration gradient exists. This allows the banded nitrogen (N) and potassium

(K) to diffuse into the soil and replace those nutrients already incorporated into the soil. Plastic

is extremely important in sustaining the moisture, otherwise the nutrients can be lost to leaching

by natural rain, or the soil may dry out and result in evaporative loss of soil moisture

(Geraldson, et al., 1965).

Methyl bromide plays an important role in the full-bed mulch process. The chemical

formulation primarily used in the Palm Beach area is 98% methyl bromide and 2% chloropicrin.

Some growers are using 67% methyl bromide and 33% chloropicrin in areas where fungal

diseases are prominent. This is due to the effective control exhibited by chloropicrin as a

fungicide.

Eggplant can be established by direct field seeding or as transplants (Hart, no date).

Transplants are usually purchased by the grower and installed in the field by machine (Shuler,

1993).

Stakes are usually placed in the rows when plants are two to three weeks old. Plastic

twine is used to tie the plant to the stake and is usually done three to four times during the

growth of the plant. Plastic twine is used due to the ease of removal by burning. Once the final

harvest is complete, plants may be killed with a herbicide such as Paraquat or Roundup. Some

growers remove old vegetation by mowing, without the aid of herbicides. Plastics are then

removed, unless a second crop is planted to re-use the plastic. Approximately 60 to 70 percent

of eggplant grown in the Palm Beach area use stakes which are either placed by every plant, or

every other plant within the row. Stakes can be removed by a stake puller and can be sterilized






by either steam or methyl bromide. However, growers in the Palm Beach area usually re-insert

the opposite end of the stake in the ground for the second crop without sterilization.


Diseases

Methyl bromide is used as a method of control for several diseases found in the

production of eggplant including damping-off, bacterial wilt, southern blight and verticillium

wilt.

Damping-off is exhibited by rotting at or below the ground level leading to the death of

the seedling. Damping-off can be caused by Fusarium, Pythium, and Rhizoctonia species.

Recommended cultural practices to control damping-off include planting in well drained soils

and not planting in areas containing large amounts of decomposed plant debris. Chemicals are

another method of disease control. The use of fungicide-treated seed can also be an effective

method of control. Table 4.8 lists chemicals used to control damping-off.





Table 4.8. Chemicals for control of damping-off.


Common Name


Chloropicrin 96.5


Methyl Bromide 98-100



Methyl Bromide 68


Methyl Bromide + Chloropicrin 67:32


Metam Sodium 32.7

Metalaxyl 25.1


Metalaxyl 25.


Trade Name


Chlor-O-Pic/Picfume

Brom-O-Gas/MC-2R

Terr-O-Gas 98 or 100

Brom-O-Sol/Brozone

MC-33/Terr-O-Gas 67


Vapam/Fume V

Ridomil

Subdue II


NOTE: For rate, use, and application to seed bed and field, refer to pp. 368-371 of the Florida
Plant Disease Control Guide, 1993.


Bacterial wilt, caused by Pseudomonas solanacearum, can express symptoms such as dark

discoloration near ground level. The plant will appear healthy with little or no signs of

yellowing prior to death. Cultural practices for control of bacterial wilt include avoiding crop

land with known disease infestation, fumigating land where seedbeds or fields are placed, and

rotating with crops that are not considered susceptible to bacterial wilt such as grass, legumes,

or cucurbits (Florida Plant Disease Control Guide, 1993). Pre-plant fumigation with methyl

bromide using various formulations containing chloropicrin is also effective for control when the

disease is present in the soil at the time of treatment.

68






Southern blight, caused by Sclerotium rolfsii, attacks the plant at or below ground level

by completely girdling the plant, thereby ceasing movement of water or nutrient to support the

upper portion of the plant. As a result, the plant wilts and eventually dies (Florida Plant Disease

Control Guide, 1993). Cultural practices for the control of southern blight include avoiding

planting in areas of known infestation and rotating with crops such as grasses, legumes, or

cucurbits (Florida Plant Disease Control Guide, 1993). Chemicals that are considered

multipurpose pre-plant fumigants include Vapam and methyl bromide. Methyl bromide

formulations containing higher concentrations of chloropicrin have been found to provide control

of southern blight if it is present at time of treatment.

Verticillium wilt, caused by Verticillium albo-atrum, affects the vigor of the plant.

Symptoms consist of diurnal wilting (where the plant regains turgor during the evening hours)

and marginal yellowing of the lower leaves of the plant. Cultural practices for the control of

Verticillium wilt include rotating with a non-susceptible crop such as grasses, legumes, or

cucurbits and avoiding planting in fields with a known history of disease (Florida Plant Disease

Control Guide, 1993). Chemicals that are considered multi-purpose pre-plant fumigants include

Vapam and methyl bromide. Methyl bromide formulations containing higher concentrations of

chloropicrin have been found to provide control of Verticillium wilt if it is present at time of

treatment.


Nematodes

There are several nematodes that have been identified in eggplant production. The most

common are: (a) root knot nematode, found in sand, muck, and rock base soils; (b) stubby-root

nematode found in sand and muck soils; and (c) sting nematode found in sand soils.






There are several fumigant and non-fumigant chemicals that are used for control of

nematodes. Two non-fumigant chemicals include Nemacur and Vydate, however these chemicals

are not considered as effective against root knot nematode as fumigant type chemicals. Fumigant

nematicides include methyl bromide plus chloropicrin (varying ratios), Vapam, Busan 1020, and

Telone II and Telone C-17 (Florida Nematode Control Guide, 1993).


Weeds

The most common weeds found in eggplant production in Florida are nightshade, eclipta

alba, goosegrass, southern crabgrass, bermuda grass, yellow nutsedge, pigweed, and morning

glory (Shuler, 1993). To reduce weed populations, several methods have been identified

including cultural control, mechanical control, and use of chemicals. To obtain effective weed

control, it is suggested to use two or more of these methods in combination.

Methods of cultural control include using plastics, planting grass in row middles, or

planting cover crops during the off season. Cover crops can be used to control populations of

undesirable plants.

Mechanical weed control includes turning the weeds under by cultivation using a disk

or plow to reduce weed infestation during the off-season or while the crop is growing. Chemical

weed control includes the use of herbicides and fumigants.

The following chemicals can be used to control weeds. DCPA (Dacthal) is used to

control germinating annuals. MCDS (Enquik) is used post-emergence for control of broadleaf

weeds in row middles. Napropamid (Devrinol) is a pre-plant incorporated for control of

germinating annuals. It must be applied prior to plastic application. Paraquat (Gramoxone) is

a contact-control for all emerged weeds. It is used in row middles between beds. Sethoxydim







(Poast) is a post-emergence spray for control of grass weeds (for application rate and comments

concerning these chemicals, refer to p. 317 of the Florida Weed Control Guide, 1993).

Fumigant type chemicals such as methyl bromide mixed with varying concentrations of

chloropicrin can be used for control of weeds prior to planting a crop. Vapam can also be used

to treat soil prior to planting a crop.


Insects

Insects such as wireworm may increase in population with the removal of methyl bromide

in eggplant production. Methods of control for wireworm include Telone and methyl bromide

(for application rates and comments regarding Telone, refer to pp. 111-112 of the Florida Insect

Control Guide). Methyl bromide is also used as a pre-plant fumigant for control of soilborne

insects.


Cucumbers

Approximately 16,000 to 23,000 acres of cucumbers are planted annually in Florida. For

the 1991-92 season 16,500 acres of fresh market cucumbers and 2,500 acres of processed

cucumbers were harvested in Florida, primarily in Collier, Manatee, Hardee, Palm Beach (East),

Hendry and Lee counties. In Florida, 2,500 acres of pickling cucumbers were harvested in the

1991-92 season (FASS, 1993). There are numerous varieties of (slicing) cucumbers such as

Dasher II, Floracuke, Early Triumph, Poinsett 76-S, Sprinter 440, and Raider. Pickling

varieties can include Addis, Calypso, or Carolina (Hochmuth, 1988d).






Cultural Practices

In cucumber production, the field should be plowed and disked to turn under old crop

residue in order to improve the efficacy of herbicides and fumigants. The soil should be

analyzed for any additional additives required, such as lime or sulfur for pH adjustment.

Disking can be used to incorporate the lime and to improve the condition of the field for bedding

(shaping the bed). The height of the bed may range from 3 to 8 inches depending on the

drainage requirements of the field. Bed formation can be accomplished using machines such as

disc hillers or bedding discs. Fertilizer and fumigation practices should be done prior to the

application of plastic mulch. If plastic is to be applied, a bed press should follow the plastic to

ensure close contact between the surface of the soil and the plastic. Advantages of plastic

include increased weed control and moisture retention, reduced leaching of fertilizer and faster

crop development. Another benefit derived from the use of mulch is reduction of belly rot

(Hochmuth, 1988d).

Application of fertilizer depends on the production system used. There are several types

of bedding production systems used in Florida including (1) non-mulched production of

cucumbers, (2) mulched production with overhead irrigation, (3) mulch production with seep

irrigation, and (4) mulch production with drip irrigation.

Non-mulched production of cucumbers requires the following for fertilizer application.

If phosphate is lacking in the soil, a band of phosphate should be applied close to the roots, due

to the immobility of the element. It may also be necessary to band micronutrients on calcareous

soils. Some micronutrients can also be applied to foliage. Under normal conditions both

phosphate and micronutrients can be incorporated into the soil. Apply 50% of nitrogen (N) and







potassium (K) at the time of planting with the remaining amount applied in a split application

during the early part of the growing season. Any additional requirements can be added as

necessary (Hochmuth, 1988d). Plastic and methyl bromide are not used in this situation.

Mulched production with overhead irrigation is similar except that it requires that total

fertilizer requirements be applied prior to the application of plastic. Mulched production using

seepage irrigation requires that total micronutrients and phosphorous (P) be incorporated into the

bed. From 10 to 15 percent of the nitrogen (N) and potassium (K) are applied prior to the

application of the mulch with the remaining amount banded in a narrow strip or groove along

the surface of the bed preceding the application of the mulch (Hochmuth, 1988d).

It is important to maintain water approximately 15 to 18 inches below, soil surface to

ensure seepage into the root zone and sustain moisture. By maintaining a moist environment,

a nutritional concentration gradient exists. This allows the banded nitrogen (N) and potassium

(K) to diffuse into the soil and replace those nutrients already incorporated into the soil. Plastic

is extremely important in sustaining the moisture, otherwise the nutrients can be lost to leaching

by natural rain, or the soil may dry out and result in evaporative loss of soil moisture

(Geraldson, et al., 1965).

Seepage irrigation can be an effective tool to limit root growth to the treated soil in the

bed area. By raising the water table, the growth of the root is restricted to the bed region.

A mulched system using drip irrigation incorporates 20 to 40 percent of the required

nitrogen (N) and potassium (K), all phosphorus (P), and micronutrients prior to planting. Any

additional requirements can be applied via the drip irrigation as needed.






Cucumbers planted using mulch with overhead, seepage or drip irrigation are usually

planted as a second crop following pepper, tomato, or eggplant. Cucumbers can benefit from

any residual effects of methyl bromide and any remaining fertilizers. It is important to

remember that there is no residual methyl bromide in the soil, however if properly applied,

population of weeds and soilborne pathogens may be reduced to the extent that the second crop

can derive benefits from the application for the first crop.

Large growers use vacuum seeders which cut a hole in the plastic and places the seed in

the hole. Smaller growers use a barrel which rolls along and punches a hole in the plastic, and

laborers riding behind the barrel manually place seeds in the hole. In non-mulched cucumber

production, a standard seeder can be used. Plantings are arranged with one row per bed, three

to four seeds per location, and approximately four feet between plants. Plug mix can also be

used, however, using plug mix is not considered a common practice.

At the end of the season of a full-bed mulch system, a machine can be used to remove

the plastic, while a cutter bar simultaneously eliminates any remaining cucumber vines.


Diseases

A cucumber crop may be grown as a second crop following a tomato, eggplant or pepper

crop. In this way, cucumbers are grown in a double cropping system using the full-bed mulch

system. Residual benefits of methyl bromide can be derived from the application for the first

crop. As a result of the initial application of methyl bromide, residual benefits can include a

decrease in populations of soilborne diseases, for the period of time in which the cucumber crop

can be successfully grown. An increase in disease activity such as damping-off and fusarium

wilt may result in the event that methyl bromide is no longer available.







Damping-off can be caused by Pythium, Rhizoctonia spp. Seeds can become infected

and fail to germinate. This disease affects cucumber seedlings, causing necrosis and death of

the plant. The soilborne fungi can invade the plant at or below the soil level (Florida Plant

Disease Control Guide, 1993).

Cultural practices recommended for control of damping-off include avoiding planting in

soils that are not conducive to favorable emergence of seedlings, using fungicide treated seeds

and planting as shallow as possible (Hochmuth, 1988d).

Table 4.9 lists chemicals that can be used for the control of damping-off. It is also

recommended that treated seed be used. Fumigant chemicals such as Telone or Vapam may also

aid in the control of soilborne diseases.



Table 4.9. Chemicals for control of damping-off.

Common Name Trade Name

Metalaxyl 2 Subdue G

Metalaxyl 25 Subdue II

Metalaxyl 25.1 Ridomil 2E


NOTE: For rate, use, and application to seed bed and field, refer to pp. 356-367 of the Florida
Plant Disease Control Guide, 1993.


Fusarium wilt is caused by Fusarium oxysporum f. sp. cucumerinum which infects the

plant at any stage of development. An overall wilting may result or individual runners may be

affected (Florida Plant Disease Control Guide, 1993).

75







Cultural practices used to control Fusarium wilt include rotation with a non-susceptible

crop on a five year rotation schedule, using crops such as crucifers, legumes, or solanaceous

plants. Chemical controls include metam sodium (for rate, use, and application to seed bed and

field, refer to the Florida Plant Disease Control Guide, 1993, pp. 356-67).


Nematodes

Methyl bromide is used to control several nematodes that pose a threat to cucumber

production, including sting and root knot nematode. Methods of control of nematodes include

avoiding planting in known infested fields and treating fields with chemicals. There are several

non-fumigant and fumigant chemicals that are used for control of nematodes. Non-fumigant

chemicals include Vydate, Mocap 10G and Mocap 10. Fumigant chemicals include Telone II

(for rate and application method refer to the Florida Nematode Control Guide, 1993, pp. 96-7).


Weeds

Several methods have been identified for controlling weed populations including crop

competition, mechanical control, mulching, and use of chemicals. To obtain effective weed

control, it is suggested to use several of these methods in combination (Hochmuth, 1988d).

Mowing, disking, hoeing, or cultivation can be effective methods of weed control. Crop

competition can be a method of control by not only increasing the number of crop plants to

effectively compete against weeds for water and nutrients, but also ensuring a healthy crop

population by using good water and nutrient management practices. The use of plastic mulch

in conjunction with fumigant chemicals can be effective in the control of many weeds. Methyl

bromide is used to control weeds such as crabgrass, panicum, goosegrass, lambsquarter, and







nutsedge. The mulch itself acts as a barrier to many weeds with the exception of nutsedge

which can grow through the plastic. The use of chemicals such as herbicides can also be used

to control weeds.

The Florida Weed Control Guide (1993) lists chemicals that can be used for weed

control. Bensulide (Prefar) is preplant incorporated for control of germinating grasses.

Bensulide+naptalam can be applied preplant or pre-emergence, for a wider range of weed

control. Diquat (Diquat) is applied post-emergence, for burdown of vines after final harvest.

Sethoxydim (Poast) is used for post-emergence control of grass weeds. Paraquat (Gramoxone)

is applied as post-emergence contact for control of all emerged weeds. It can be used in row

middles between beds, or it can also be applied as a pre-emergence application. Ethalfluralin

(Curbit) is applied either pre-emergence or post-emergence for control of grasses such as goose

grass, panicum, or lambsquarter. Glyphosate (Roundup) is used prior to planting for removal

of weeds. Naptalam (Alanap) is applied pre-emergence for control of germinating annuals such

as lambsquarter, pigweed and carpet weed. This chemical can also be applied post-emergence

immediately after transplant for control of annual weeds. Other herbicides include Clomoxone

(Command 4EC) applied preplant and DCPA (Dacthal W-75) applied as an early post-emergent

(for application rate and comments, regarding these chemicals refer to the Florida Weed Control

Guide, 1993, pp. 312-6).


Insects

In cucumber production, insects such as wireworm may increase in populations with the

removal of methyl bromide. Methods of control for wireworm include Diazinon, a non-fumigant







chemical which controls wireworm and Telone which is a fumigant (for application rates and

comments, refer to pp. 441-446 of the 1992-1993 Florida Insect Control Guide, 1993).


Squash

Squash is grown throughout the state of Florida with the exception of the Everglades

region. The primary squash production area is located in southeast Florida. Squash is harvested

from early September to July. Summer varieties that are harvested immature include: Cracker,

Sundance, and Lemondrop. Winter varieties that are harvested mature include: Royal Acorn,

Tay Belle, and Ponca. There are numerous other varieties that are also grown in Florida (Olson

and Sherman, No Date). In the 1991-92 season, approximately 12,500 acres of squash were

harvested in the state of Florida (FASS, 1993).


Cultural Practices

Squash can be planted as a single crop without mulch and as a second, and sometimes

third crop, in a multiple cropping system, using the full-bed mulch system.

In Florida, squash grown as a single crop uses the open bed system which does not

require plastic or the use of methyl bromide. The field is plowed and checked for leveling,

especially in areas where seepage irrigation is to be used. Soil requirements are tested, and soil

amendments are applied, such as lime for adjustment of pH. Disking may be required to

prepare the field for planting (Kostewicz, 1976). The development of slightly raised beds may

be required in areas where flooding may occur. This can be accomplished using a disc hiller

or a bed disc. The initial application of fertilizer is applied as a band or strip 2 to 3 inches to

the side of and below the seed. Supplemental fertilizer should be applied as needed during the







growing season (Olson and Sherman, No Date). Irrigation can be supplied via overhead or

seepage system.

Squash is also planted as a second crop in a double cropping system following either a

tomato or pepper crop. The double cropping system may use the full-bed mulch system

requiring the use of plastic in conjunction with methyl bromide (Hochmuth, 1993). Methyl

bromide is not registered for use in squash production, however, when squash is planted as a

second crop following tomato or pepper, it can benefit from the residual effects of methyl

bromide from the initial application for the first crop.

The following is a description of a sequence of operations that may occur during the

installation of the full-bed mulch system. The field should be plowed and checked for leveling,

especially in areas where seepage irrigation is to be used. Soil requirements are tested, and soil

amendments are applied, such as lime for adjustment of pH. Disking may be required to

prepare the field for planting. A bed disc or disc hiller can then be used to shape the beds. A

bed press may follow to ensure good contact between the surface of the bed and the plastic. All

chemical and fertilizer requirements are applied prior to installation of the plastic. After

completed harvest of first crop (such as tomato or pepper), an application of a herbicide, such

as paraquat, can be used to kill any remaining vines. A cutter bar or mower may then be used

to remove any remaining debris. Squash may then be direct seeded into the same bed.

Additional application of fertilizer, such as nitrogen (N) and potassium (K), may be required and

can be injected via an injection wheel or drip system if the drip system is already in place.

Irrigation requirements can be met by the use of seepage, drip, or overhead irrigation.






Diseases

Methyl bromide is used as a method of control for several diseases found in squash

production. One of the more prevalent diseases found in squash is damping-off.

Damping-off can be caused by Phythium spp. and Rhizoctonia solani. This disease can

affect young plants causing the plant to collapse at the soil line, and it can cause seeds not to

germinate (Florida Plant Disease Control Guide, 1993). A cultural method of control for

damping-off includes avoiding planting in soils that have unfavorable moisture and temperature

regimes. The chemical control methods for damping-off are listed in Table 4.10.



Table 4.10. Chemicals for the control of damping-off.

Common Name Trade Name


metalaxyl 2 Subdue G

metalaxyl 25 Subdue II

metalaxyl 25.1 Ridomil 2E

metalaxyl Ridomil 2E


NOTE: For rate, use, and application ethods, refer to the Florida
Plant Disease Control Guide, 1993, pp. 410-6.






Nematodes

Methyl bromide is used to control several nematodes that may pose a threat to squash,

including sting and root knot nematode. Symptoms occurring with sting or root knot nematodes

include stunting, chlorotic appearance, wilting of the plant and galling or a stubby root system.

Cultural control methods for nematodes include allowing land to remain fallow, rotating

to a different crop, and flooding. However, it is recommended not to plant in fields heavily

infested with nematodes (Olson and Sherman, no date).

Chemical control methods for nematodes include Vydate L, a non-fumigant, and Telone

II and Telone C-17, a fumigant chemical (for additional information refer to the Florida

Nematode Control Guide, 1993).


Weeds

To reduce weed populations, several weed control methods have been identified,

including crop competition, mechanical control, mulch, and herbicides. In order to increase

effectiveness, it is recommended to use at least two of these methods together. Establishment

of a good crop stand can shade the ground and reduce germination of weeds. Mechanical

control, such as light disking, can control weeds, however, additional weeds may result because

some weeds require disturbance of the soil in order to germinate. Use of mulch in conjunction

with fumigants can be effective for weed control. Plastic mulch can aid in the control of weeds

by acting as a barrier. However, nutsedge will still grow through plastic (Florida Weed Control

Guide, 1993). Table 4.11 contains a list of chemicals that are used in the production of squash.







Table 4.11. Chemicals for the control of weeds in squash production.


Herbicide Time of application Rate (lbs. AI./Acre) Mineral
6

DCPA Early post-emergence 8-10

(Dacthal W-75)

Diquat Burndown of vines 0.25

(Diquat H/A after harvest

Glyphosate Prior to planting 0.5-1.0

(Roundup)

Paraquat Pre-plant or pre- 0.63-0.94

(Gramoxone Extra) emergence

Sethoxydim Post-emergence 0.188-0.28

(Poast)


Source: Florida Weed Control Guide, 1993.




Insects

In squash production, insects such as wireworm may increase in population with the

removal of methyl bromide. Methods of control for wireworm include Diazinon, a non-

fumigant, and Telone I and Telone C-17, a fumigant chemical (Florida Insect Control Guide,

1993).







Fresh Citrus


An important use of methyl bromide is as a post-harvest fumigant for agricultural

products. In Florida, citrus is the most important user of methyl bromide on a post-harvest

basis.

Although the majority of Florida citrus is processed into juice, fresh marketing still

represent an important source of revenue to Florida citrus producers. In Table 4.12, the

production and utilization of oranges, grapefruit, and tangerines is presented. Note that while

over 90 percent of Florida-produced oranges are typically processed, approximately 50 percent

of the grapefruit grown in Florida and over 60 percent of the tangerines produced in Florida are

marketed in fresh form.

Fumigation is used in Florida citrus mainly to kill fruit flies which are found sporadically

in the state. While fruit flies may be found throughout the citrus producing region in the state,

only fresh citrus fruit destined for domestic markets in other citrus producing states (California,

Arizona, Texas, and Hawaii) is routinely fumigated. The number of cartons of fresh citrus

fumigated in Florida over the 1984 to 1993 period is shown in Table 4.13.

There are two major types of grapefruit produced in Florida: white seedless and red

seedless1. In Table 4.14, production and utilization of white seedless grapefruit is presented.

Inspection of this table suggests that while a large proportion of white seedless grapefruit is

processed, exports of fresh white seedless grapefruit has expanded over the past decade. In



'Both pink seedless and red seedless varieties are grown in Florida. While the USDA uses
the term "colored" to categorize both pink and red seedless fruit, the terminology most widely
used in the industry is to simply refer to all varieties which are not white as "red seedless
grapefruit". This convention is adopted in this study.

83








Florida citrus: utilization of production (1000 boxes).


Oranges Grapefruit Tangerines
Season Fresh Processed Fresh Processed Fresh Processed
1983-84 7,640 109,060 16,661 24,239 1,858 1,117
1984-85 6,652 97,248 14,988 29,012 945 895
1985-86 8,960 110,240 19,620 27,130 1,189 761
1986-87 8,870 110,830 20,938 28,862 1,462 878
1987-88 9,520 128,480 23,110 30,740 1,614 836
1988-89 8,488 138,112 23,902 30,848 1,639 1,261
1989-90 5,922 104,278 13,344 22,356 999 701
1990-91 12,451 139,149 23,923 21,177 1,227 723
1991-92 11,552 128,248 22,841 19,559 1,965 635
1992-93 10,693 175,807 23,156 31,994 2,065 735


Source: Citrus Summary, various issues.







Table 4.13. Florida citrus fumigated with methyl bromide.


Number of Cartons


Season
1984-85
1985-86
1986-87
1987-88
1988-89
1989-90
1990-91
1991-92
1992-93


67,100
92,400
67,200
459,900
242,452
520,275
4,190,050
3,281,843
1,340,345


Source: Florida Department of Agriculture.


Table 4.12.







Utilization of certified Florida white grapefruit, 1980-81 through 1992-93.


Year Fresh Export Processed Total
-------------- 00boxes--- -----------
1980-81 4,671 2,984 20,205 27,860
1981-82 4,638 3,231 18,968 26,837
1982-83 5,420 3,112 12,750 21,282
1983-84 4,121 3,036 15,347 22,504
1984-85 4,061 1,196 19,445 24,702
1985-86 3,752 2,890 18,863 25,505
1986-87 2,928 4,040 19,812 26,780
1987-88 2,430 5,378 21,179 28,987
1988-89 2,088 5,635 19,666 27,389
1989-90' 1,178 2,637 13,946 17,761
1990-91' 1,988 5,901 13,506 21,395
1991-92' 1,144 5,257 12,339 18,740
1992-93* 1,155 4,516 19,615 25,286

'Includes Canada in Export.
Source: Division of Fruit and Vegetable Inspection, Florida Department of Agriculture.

Table 4.15. Utilization of certified Florida red grapefruit, 1980-81 through 1992-93.
Year Fresh Export Processed Total
-----------------------1000boxes---------------------
1980-81 6,284 2,136 5,698 14,118
1981-82 6,240 1,736 6,405 14,381
1982-83 7,121 1,650 3,531 12,302
1983-84 6,726 1,940 4,371 13,037
1984-85 7,874 1,636 6,653 16,163
1985-86 10,041 2,649 5,111 17,801
1986-87 9,915 3,698 6,143 19,756
1987-88 9,831 4,959 6,807 21,597
1988-89 9,309 6,149 7,830 23,288
1989-90' 5,967 3,072 7,010 16,049
1990-91' 9,746 5,584 6,067 21,397
1991-92' 9,975 5,554 6,002 21,531
1992-93' 10,297 6,130 10,631 27,058

'Includes Canada in Export.
Source: Division of Fruit and Vegetable Inspection, Florida Department of Agriculture.


Table 4.14.





In particular, the opening of the Japanese fresh citrus market has resulted in large increases

of shipments of fresh white seedless grapefruit to Japan. In Table 4.15, production and

utilization of pink seedless grapefruit production is shown. The primary market outlet for pink

seedless grapefruit has always been the fresh market. Production of pink seedless grapefruit in

Florida has expanded rapidly over the past decade. By the 1991-92 season, pink seedless

grapefruit has overtaken white seedless grapefruit as the most important grapefruit variety

produced in Florida.

While the percentage of fresh citrus marketing from Florida that has been fumigated has

historically been small, the major impact of a methyl bromide ban on the Florida citrus industry

is that no viable alternative exists as a post harvest control for fruit fly. Thus, a ban on methyl

bromide is likely to result in the loss of markets in other citrus producing states, namely

California, Hawaii, Arizona, and Texas.

It is important to note that the export market for fresh Florida citrus will not be affected

by a methyl bromide ban. Both European and Asian markets have refused to accept fruit which

has been fumigated with methyl bromide. Therefore no methyl bromide treated product has

been shipped to those markets in recent years.

As methyl bromide is used only in the post harvest fumigation of citrus destined for the

fresh market, a ban of methly bromide would have no direct effect on the processed citrus

industry. It is possible, however, that with no alternative available to fumigate fruit destined

for other citrus producing states, a ban of methyl bromide might result in an increase of

processed utilization at the expense of fresh market utilization.







SECTION 5

THE ECONOMIC IMPACT OF A METHYL BROMIDE BAN

Objectives

The objective of the economic analysis is to quantify the effect a ban on methyl bromide

use is expected to have on the state of Florida. Methyl bromide has been identified as a critical

chemical for the efficient production of several vegetable crops and in the marketing of fresh

citrus. It is used as a soil fumigant in several vegetables and fruit and as a fumigant for fresh

citrus packaging prior to shipping to other areas susceptible to crop or product damaging pests

common to the shipping area.

The vegetable and fruit crops analyzed in this research are those crops which are likely

to be most impacted if methyl bromide is no longer available as a soil fumigant. Those crops

identified included tomatoes, bell peppers, cucumbers, squash, eggplant, strawberries and

watermelons. Not all of these crops require methyl bromide to be used as a soil fumigant in all

circumstances, however, methyl bromide may impact the economic outcome of all production

systems because of production losses in crop production systems where methyl bromide is used.

Citrus is impacted because methyl bromide is used on fresh citrus as a post harvest

fumigant prior to shipping. No fresh citrus from Florida is allowed to be shipped to California,

Texas, Arizona, and Hawaii without fumigation of the packed fruit because of the danger of

carrying fruit fly from Florida into one of these producing areas. A ban on the use of methyl

bromide would currently eliminate these states as markets for Florida fresh citrus because no

effective alternative exists for methyl bromide for post harvest use.







The Impact on the Production of Vegetables from a Ban on Methyl Bromide


Methodology

Methyl bromide has been identified as a critical soil fumigant used in the production of

several vegetable and fruit crops, those being tomatoes, bell peppers, cucumbers, eggplant,

squash, strawberries and watermelons. While methyl bromide may not be critical to all crops

in all production systems, it is currently used in each of these crops in some production systems

within some production areas in Florida.

Production of these crops are economic enterprises that growers produce in expectation

of a positive return to their investments. These crops compete with each other and other crops

and enterprises for resources used in their production. Growers of these crops also compete

with other producers who can produce and ship these same products during the season that

Florida growers have them available.

A partial equilibrium model can be used to evaluate the effects a change in the industry

may have on the production and marketing of various crops from various regions. In the model

used here (see Appendix E for a more detailed discussion of the model), these crops were

modeled in a monthly model considering production from each of the major producing regions

in Florida and from other regions in the U.S. and Mexico which grow and sell during Florida's

season. See Appendix D for further discussion of the crops, months, and competing regions

included in the economic analysis.2



2As noted in Appendix D, two separate analyses are conducted. One analysis encompasses
those fruit and vegetable crops which are annuals, e.g. tomatoes, peppers, etc.; the other
analysis deals with the perennial crops, namely citrus.

88