Citation
Sweet potatoes : managing pesticides for crop production and water quality protection : a supplement to the IFAS pest control guides

Material Information

Title:
Sweet potatoes : managing pesticides for crop production and water quality protection : a supplement to the IFAS pest control guides
Series Title:
Circular - Florida Cooperative Extension Service - 1008 (Water quality initiative series)
Creator:
Buttler, T. M.
Affiliation:
University of Florida -- Florida Cooperative Extension Service -- Department of Soil Sciences -- Institute of Food and Agricultural Sciences
Place of Publication:
Gainesville, Fla.
Publisher:
Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Publication Date:
Language:
English
Physical Description:
10 p. ; 28 cm.

Subjects

Subjects / Keywords:
Agriculture ( LCSH )
Farm life ( LCSH )
Farming ( LCSH )
University of Florida. ( LCSH )
Sweet potatoes -- Diseases and pests -- Control -- Environmental aspects -- Florida ( LCSH )
Pesticides -- Environmental aspects -- Florida ( LCSH )
Soil surveys -- Florida ( LCSH )
Agriculture -- Florida ( LCSH )
Spatial Coverage:
North America -- United States -- Florida
North America -- United States of America -- Florida

Notes

Funding:
Florida Historical Agriculture and Rural Life

Record Information

Source Institution:
Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location:
Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management:
All rights reserved, Board of Trustees of the University of Florida
Resource Identifier:
25052273 ( OCLC )
AJB7124 ( NOTIS )
026779638 ( ALEPH )

Full Text




Soil Science Department
Water Quality Initiative Series


Circular 1008
May 1991


SWEET POTATOES


MANAGING PESTICIDES FOR CROP PRODUCTION

AND WATER QUALITY PROTECTION

A Supplement to the IFAS Pest Control Guides


T. M. BUTLER
and
A. G. HORNSBY
Soil Science Department

W. M. STALL
Vegetable Crops Department

F. A. JOHNSON
Entomology and Nematology Department

J. W. NOLING
CREC, Lake Alfred, FL

T. A. KUCHAREK
Plant Pathology Department
Institute of Food and Agricultural Sciences
University of Florida
Gainesville, FL 32611




Florida Cooperative Extension Service
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
John T. Woeste, Dean for Extension









WATER QUALITY CONSIDERATIONS IN
SWEET POTATO PRODUCTION

Concern about the harmful effects of pesticides on
surface water and groundwater quality should
motivate sweet potato growers to select pesticides
with the least potential to cause water quality
problems. Many sweet potato growers live in rural
areas near where they and other growers raise
sweet potatoes, therefore, their personal water
supply is susceptible to contamination.
Unfortunately, information that allows growers to
select pesticides less likely to affect water quality
has not previously been readily available.

Our purpose is to provide information that can help
growers select pesticides that will have a minimum
adverse impact on water quality. The procedure
considers the soil properties of the application site,
the mobility of pesticides in these soils, and the
toxicity of the pesticides in water to humans and
aquatic species. A proper selection will decrease
chances of adversely affecting surface water and
groundwater quality. Certain combinations of soil
and pesticide properties (along with weather
conditions) can pose a significant potential hazard
to water quality. Our goal is to identify and avoid
these circumstances. Information contained in this
report can help sweet potato growers make better
decisions about the pesticides that they use. This
document in no way endorses any particular pest
control product. All products must be used in
accordance with the label.


MATERIALS NEEDED TO USE THIS
PROCEDURE

To effectively use this procedure you will need the
following source materials:

1. A copy of the current IFAS Pest Control Guides
or other appropriate information sources that
identify pesticides that control specific pests.

2. A copy of your county soil survey report to
identify the soil types found in your fields.

3. A copy of the Soil Science Fact Sheet entitled
"[Name of your countv]:Soil Ratings for Selecting
Pesticides" for your county, available from your
county Cooperative Extension Office. The basis of
these ratings are given in the IFAS Extension


Circular 959 entitled "Soil Ratings for Selecting
Pesticides for Water Quality Goals," which is also
available from your county Cooperative Extension
Office.

Note: If your county has not yet been mapped by
the Soil Conservation Service, you will need to
contact the local SCS office for a site evaluation and
determination of soil types and ratings for leaching
and runoff of pesticides.


IMPORTANT FACTORS
PESTICIDE SELECTION


THAT AFFECT


How pesticides behave in the soil is determined by
many factors including properties of the pesticides
and of the soil at the application site. Some of the
factors that should be considered when selecting
pesticides with minimal potential for water quality
impacts are:

Pesticide properties 1) The organic carbon
adsorption coefficient, K.I describes the relative
affinity or attraction of the pesticide to soil
materials and therefore its mobility in the soil. 2)
The biological degradation half-life, T, is a
measure of persistence of the pesticide in soil. 3)
The lifetime health advisory level or equivalent,
HALEQ, is a measure of health risk to humans of
pesticide contaminated drinking water. 4) Aquatic
toxicity, LCs is a measure of the ability of the
pesticide to cause 50% mortality in aquatic test
species.

Soil properties 1) Hydraulic permeability is a
measure of the soils ability to allow water to
percolate through it. 2) Organic matter is
important for providing binding sites for pesticides,
thus reducing their mobility and increasing their
opportunity to be degraded by soil microorganisms.
3) Slope affects the potential for water to run off
the land surface.

Management practices 1) Pesticide application
frequencies and rates determine the total amount
applied. Lower frequencies and rates reduce the
potential for contamination. 2) Application
methods affect the amount of pesticide subject to
transport by water. For example, if applied directly
to the soil, there is a greater probability that more
of the product will be available for leaching or
runoff than if applied to the foliage. If the product


2









is incorporated into the soil, leaching may be the
most important loss pathway. Pesticides applied to
the foliage may be lost to the atmosphere,
decomposed by sunlight, or absorbed by the foliage,
thereby reducing the amount available for wash-off
and transport to water bodies. Irrigation practices
can also determine the loss pathways of pesticides.
Pesticides often move with water, so the less excess
water that is applied the less potential there is for
a pesticide to move past the crop root zone or to
run off in surface water. Rainfall or overhead
irrigation can wash off significant quantities of
pesticides from foliage immediately after
application.


INDICES USED TO SELECT PESTICIDES

Table 1 contains two important indices, the
pesticide leaching potential (RLPI) and the
pesticide runoff potential (RRPI). Both indices are
relative. For a given soil, these indices rank the
pesticides by their potential to move from the
application site by the indicated pathway (leaching
or runoff). The indices are based on the organic
carbon sorption coefficient and degradation half-life
values of each pesticide. Values for these
parameters have been taken from scientific
literature, technical manuals, and company product
literature.

The Relative Leaching Potential Index (RLPI)
defines the relative attenuation (reduction in mass
as it moves through the soil) of each pesticide in
soil, and therefore its potential to leach to
groundwater. Pesticides that are very mobile, for
example, those that have Ko values less than 100 in
sandy soils, or 50 or less in fine-textured soils
should be used with caution. There is some
uncertainty in the data used to calculate this index.
However, since the values are relative they can still
be used. It is important to realize that the smaller
the RLPI value of a pesticide the greater is its
potential to leach.


The Relative Runoff Potential Index (RRPI)
defines the relative immobility and availability of
each pesticide in soil, and therefore its potential to
remain near the soil surface and be subject to loss
in the aqueous phase or sediment phase of runoff.
There is some uncertainty in the data used to
calculate this index. However, since the values are


relative they can still be used. The smaller the
RRPI value of a pesticide the greater is its potential
to be lost in runoff.

Table 1 also contains information on the toxicity of
pesticides to humans and aquatic species. This
information can be used as a secondary
consideration in the pesticide selection procedure.


The Lifetime Health Advisory Level or Equivalent
(HALEQ) provides a measure of pesticide toxicity
to humans. The lifetime health advisory level as
defined by the USEPA is the concentration of a
chemical in drinking water that is not expected to
cause any adverse health effects over a lifetime of
exposure (70 years), with a margin of safety. The
values in Table 1 are the USEPA lifetime health
advisory level, HAL, or an equivalent value,
HALEQ (denoted by a superscripted asterisk),
calculated using the same formula used by the
USEPA (HALEQ = RfD x 7000), where RfD is
the reference dose determined by the USEPA. For
non-carcinogenic pesticides the calculated HALEQ
should not differ by more than a factor of 10 from
the values forthcoming from the USEPA. The
HAL or HALEQ has units of micrograms per liter
(tig/1, or ppb). The smaller the value the greater is
the toxicity to humans.

The Aquatic Toxicity provides a measure of
pesticide toxicity to aquatic species. The values
given in Table 1 are the lethal concentrations at
which 50% of the test species die (LC, ). Unless
otherwise noted by a lower case letter following the
value, the test species was rainbow trout. The
smaller the value the greater is the toxicity to
aquatic species.

Data for KI, RLPI, RRPI, HALEQ, and aquatic
toxicity are given for the active ingredient (common
name) of a product. When using a product that is
a mixture of two or more active ingredients use the
RLPI, RRPI, HALEQ, and Aquatic Toxicity value
for the most restrictive active ingredient in the
mixture.

Important Note: The information presented in
Table 1 DOES NOT supersede or replace the
information on the pesticide container label or
product literature.


3









CRITERIA FOR MATCHING SOIL RATINGS WITH PESTICIDE INDICES


Pesticides with less potential to adversely affect water quality can be selected by matching the soil ratings and
pesticides using the following criteria:

PESTICIDE SELECTION CRITERIA


IF SOIL RATINGS
ARE:


THEN
SELECT PESTICIDE WITH:


RUNOFF


LOW

LOW

LOW


MEDIUM


MEDIUM


MEDIUM


HIGH


HIGH


HIGH


Larger RLPI value,

Larger RLPI value,

Larger RLPI and
RRPI values,

Larger RLPI and
RRPI values,

Larger RLPI and
RRPI values,

Larger RRPI value,


Larger RLPI and
RRPI values,

Larger RRPI and
RLPI values,

Larger RRPI value,


AND Larger HALEQ value.

AND Larger HALEQ value.

AND Larger HALEQ and
Aquatic Toxicity values.

AND Larger HALEQ and
Aquatic Toxicity values.

AND Larger HALEQ and
Aquatic Toxicity values.

AND Larger Aquatic Toxicity
value.

AND Larger HALEQ and
Aquatic Toxicity values.

AND Larger Aquatic Toxicity
and HALEQ values.

AND Larger Aquatic Toxicity
value.


PROCEDURE FOR SELECTING PESTICIDES
TO REDUCE ADVERSE WATER QUALITY
IMPACTS

A "Pesticide Selection Worksheet" is provided as a
convenient way to organize the information needed
to select pesticides to avoid water pollution by
pesticides in a particular production or management
unit. Instructions for using the worksheet are
outlined below. The function of the worksheet is to
match the soil leach and runoff ratings at the
application site with the pesticide RLPI (leaching)
and RRPI (runoff) indices and toxicity values given
in Table 1.


This will indicate the relative potential for pesticides
to leach or run off from a particular site and
consider the toxicity of the pesticides to humans or
aquatic life if the pesticides leach into groundwater
or if runoff enters surface impoundments or
streams. The last two columns are for recording the
sweet potato grower's choices and reasons for
selecting particular products.

Our intent is to provide a decision support tool for
the sweet potato grower. The grower is responsible
for making the final choice. The completed
worksheet can serve as a permanent record of the
selection process used and decision made by the
grower.


4


LEACH

HIGH


MEDIUM


LOW


HIGH


MEDIUM


LOW


HIGH


MEDIUM


LOW









USING THE WORKSHEET


1. TARGET PEST: Correct identification of the
pests that need to be controlled is essential! Check
with knowledgeable experts and utilize competent
diagnostic laboratories so that a proper diagnosis
can be made. Misdiagnosis results in the wasteful
use of unnecessary pesticides and needless increases
in production costs. List confirmed pests in column
1 of the Pesticide Selection Worksheet.


2. RECOMMENDED PESTICIDES: Use the
current IFAS Pest Control Guides, or other
appropriate information sources to identify the
pesticides that control the pests of concern. List
these pesticides in column 2 of the Pesticide
Selection Worksheet.


3. PESTICIDE PROPERTIES: For each pesticide
listed in column 2 on the Pesticide Selection
Worksheet, copy the numeric value for KI, RLPI,
RRPI, HALEQ, and Aquatic Toxicity from Table 1
into columns 3, 4, 5, 6, and 7 of the Pesticide
Selection Worksheet.


4. SOIL PROPERTIES: Consult the County Soil
Survey Report soil map sheets to locate your
production fields and to identify the soils that occur
in these fields. Use the Soil Science Fact Sheet
entitled "[Your County]:Soil Ratings for Selecting
Pesticides" (available from your county Cooperative
Extension Office) to determine the leaching and
surface runoff rating of the soils in your fields. As
you determine the soil leach rating and the soil
runoff rating for each soil in each field, list the soil
name, soil leach rating, and soil runoff rating in
columns 8, 9, and 10, respectively, of the Pesticide
Selection Worksheet.


5. SELECTION OF PESTICIDES: Using infor-
mation that you have compiled on the Pesticide
Selection Worksheet, select appropriate pesticides
using the selection criteria on page 4 to match soil
and pesticide properties. The selection made can
be recorded in column 11 and notes relating to the
selection can be recorded in column 12.


Notes:
1. If the pesticide product selected is a formulated
mixture or a tank mix, each active ingredient must
be considered. The most restrictive pesticide in the
mixture will determine the choice. Trade names in
Table 1 followed by (M) are formulated mixtures.

2. Sometimes there may not be a clear choice from
among the alternative chemicals available to control
a particular pest. In these cases, first order
screening using the RLPI or RRPI only can suffice.

3. Depth to groundwater and local geohydrology
may influence your final selection. Shallow
groundwater is more vulnerable to contamination.
Deep water tables with intervening impermeable
geologic layers are much less vulnerable.

4. Distance to surface water bodies may also
influence your final selection. Surface waters
adjacent to or near the pesticide application site are
more vulnerable to contamination than those further
away. If surface runoff from the application site
usually infiltrates into the soil off site before
reaching a surface water body, then the HALEQ
should be considered as the secondary screening
index.


5











TABLE 1. Sweet Potatoes Pesticide Parameter Matrix for Selectina Pesticides to Minimize Water Quality Problems.


Sorption Relative Losses Toxicity
Application Type2 Coefficient3 Leaching Runoff HAL or HALEQ6 Aquatic LC7
Trade Name1 Common Name Soil Foliar Ko (ml/g) RLPI4 RRPI5 (ppb) (ppm)


Herbicide


Amiben
Dacthal
Eptam
Fusillade 2000
Roundup


chloramben
DCPA
EPTC
fluazifop-butyl
glyphosate


x
x
INC


15
5,000
200
5,700
24,000


x
x


E



E


11
500
333
>2,000
>2,000


Insecticide/Miticide


Cythion
Dasanit
Dazzel
Knox-Out
Lorsban
Martate
Meticide
Mocap
Niran
Noxfire
PB Nox(M)
PB Nox(M)
Sevin
Temik
Thiodan
Thuricide


Nematicide


Dasanit
Mocap
Temik


malathion
fensulfothion
diazinon
diazinon
chlorpyrifos
methoxychlor
methyl-parathion
ethoprop
parathion
rotenone
rotenone
piperonyl butoxide
carbaryl
aldicarb
endosulfan
Bacillus thuringiensis


fensulfothion
ethoprop
aldicarb


x


x
INC
INC
x


INC
INC





x


x
x

x
x

x
x
x
x
x

x
x


1,800
89
1,000
1,000
6,070
80,000
5,100
70
5,000
772
772
nd
300
30
12,400
nd


INC
INC
INC


E
E


E

E


89
70
30


>2,000
37
250
250
>2,000
>2,000
>2,000
28
>2,000
nd
nd
nd
300
10
>2,000
nd


37
28
10


HAL or HALEQ6: Lifetime Health Advisory Level or Lifetime Health Advisory Level Equivalent.

Continued---


6


11
2
333
12
1


100
4,000
200
70
700


*
*


non toxic
100a
17
1.6
8.3


556
37
25
25
5
1
39
28
14
nd
nd
nd
300
10
2
nd


200
2
0.6
0.6
20
400
2
0.1
2
30
30
100
700
10
0.4
nd


*
*
*



*
*
*
*
*


*


*
*


0.2
8.8
0.09
0.09
0.0071
0.062
3.7
13.8
1.43
0.031
0.031
0.0034
114
0.56
0.0014
95b


8.8
13.8
0.56


37
28
10


2
0.1
10


05/01/91









TABLE 1. Sweet Potatoes Pesticide Parameter Matrix---Continued:


Sorption Relative Losses Toxicity
Application Type2 Coefficient3 Leaching Runoff HAL or HALEQ6 Aquatic LC7
Trade Name1 Common Name Soil Foliar Ko (ml/g) RLPI4 RRPI5 (ppb) (ppm)

Fungicide

Botran DCNA x 1,000 E 167 17 200 7
Mertect thiabendazole x 2,500 62 1 700 Low toxicity
Thiram thiram x 670 447 100 40 0.13


Fumigants for Control of Soil Fungi and Nematodes

Brom-O-Gas methyl bromide INJ 22 4 4 7 2.5
Chlor-O-Pic chloropicrin INJ 62 620 620 nd nd
Dowfume MC2 methyl bromide INJ 22 4 4 7 2.5
Fume V metam-sodium INJ 10 E 14 14 nd 0.39b
Telone II 1,3-dichloropropene INJ 32 32 32 0.2 5.5
Telone C-17(M) chloropicrin INJ 62 620 620 nd nd
Telone C-17(M) 1,3-dichloropropene INJ 32 32 32 0.2 5.5
Terr-O-Gas (M) methyl bromide INJ 22 4 4 7 2.5
Terr-O-Gas (M) chloropicrin INJ 62 620 620 nd nd
Vapam metam sodium INJ 10 E 14 14 nd 0.39b
Vortex (M) M.I.T. INJ 6 9 9 nd 0.37
Vortex (M) 1,3-dichloropropene INJ 32 32 32 0.2 5.5


1Trade Name: (M) indicates that the product is a mixture of two or more active ingredients.
2Application Type: INC: incorporated INJ: injected x: applied to soil surface or foliage
3Sorption Coefficient: E: estimated G: educated guess
4Relative Leaching Potential Index (RLPI): Smaller number indicates greater leaching hazard.
5Relative Runoff Potential Index (RRPI): Smaller number indicates greater runoff hazard.
6HAL or HALEQ: Lifetime Health Advisory Level or Lifetime Health Advisory Level Equivalent.
*: Lifetime Health Advisory Equivalent
Aquatic Toxicity LC50: value is for rainbow trout 48 or 96 hr exposure time, unless otherwise specified
a=channel catfish b=bluegill d=goldfish
nd: no data available.







7







PESTICIDE SELECTION WORKSHEET


Landowner/Operator Name:

Crop:


Farm IDTn


County: Oate---


Field ID Sheet of


IFAS Relative Losses Toxicity Soil Soil
Target Pest Recommended Ko Leaching Runoff Lifetime Aquatic Soil Leaching Runoff Selected Comments
Pesticides Value RLPI RRPI HALEQ* Toxicity Type Rating Rating Pesticide
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)











































If the Kc value is 100 or less or if the RLPI value is 10 or less and the soil leach rating is high, then the pesticide has a high potential for leaching and should
be used with extreme caution. Alternative pesticides and reduced rates should be considered if possible. Apply pesticide during periods with low potential for rainfall
if possible.


8


County:


Date


Farm ID:





PESTICIDE SELECTION WORKSHEET


Landowner/Operator Name:

Crop:


Countv-


Farm ID:


nate-


Field ID Sheet of


IFAS Relative Losses Toxicity Soil Soil
Target Pest Recommended Km Leaching Runoff Lifetime Aquatic Soil Leaching Runoff Selected Comments
Pesticides Value RLPI RRPI HALEQ* Toxicity Type Rating Rating Pesticide
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)


the Ko value is 100 or less or if the RLPI value is 10 or less and the soil Leach rating is high, then the pesticide has a high potential for teaching and should
used with extreme caution. Alternative pesticides and reduced rates should be considered if possible. Apply pesticide during periods with low potential for rainfall
possible.


9


If
be
if


-`-~-









Acknowledgements:


The development of this document was supported by the USDA/ES Water Quality Initiative Project
#89EWQI-1-9134 and the IFAS Center for Natural Resources, University of Florida, Gainesville, FL.


10
















































































COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLORIDA, INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES,John T. Woeste,
Director, in cooperation with the United States Department of Agriculture, publishes this information to further the purpose of the May 8 and June
30,1914 Acts of Congress; and is authorized to provide research, educational information and other services only to individuals and institutions that
function without regard to race, color, sex, age, handicap or national origin. Single copies of extension publications (excluding 4-H and youth
publications) are available free to Florida residents from county extension offices. Information on bulk rates or copies for out-of-state purchasers
is availablefrom C.M. Hinton, Publications Distribution Center, IAS Building 664, Universityof Florida, Gainesville, Florida32611. Before publicizing
this publication, editors should contact this address to determine availability. Printed 10/91.