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 Introduction
 Sequential control practices for...
 Table 3: Diseases of peanut found...
 Table 4: Fungicides for suppressing...






Group Title: Extension plant pathology reports
Title: Disease control program for peanuts
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Permanent Link: http://ufdc.ufl.edu/UF00066915/00001
 Material Information
Title: Disease control program for peanuts
Series Title: Extension Plant Pathology Report 12
Physical Description: Book
Language: English
Creator: Kucharek, Tom
Affiliation: University of Florida -- Florida Cooperative Extension Service -- Department of Plant Pathology -- Institute of Food and Agricultural Sciences
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Publication Date: 2005
 Subjects
Spatial Coverage: North America -- United States of America -- Florida
 Notes
Funding: Florida Historical Agriculture and Rural Life
 Record Information
Bibliographic ID: UF00066915
Volume ID: VID00001
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 by the source institution and holding location.

Table of Contents
    Introduction
        Page 1
    Sequential control practices for peanut diseases
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
    Table 3: Diseases of peanut found in Florida
        Page 13
        Page 14
    Table 4: Fungicides for suppressing peanut diseases
        Page 15
        Page 16
Full Text












EXTENSION PLANT PATHOLOGY REPORT NO. 12
GAINESVILLE, FLORIDA JANUARY, 2005
(Revision No. 24)

by Tom Kucharek

DISEASE CONTROL PROGRAM
FOR PEANUTS

INTRODUCTION

Peanut diseases reduce yields and monetary returns by retarding desirable plant development or
by diverting product utilization. Some diseases, such as leaf spot and rust, are obvious while others,
such as root rots and pod rots, often are unnoticed until dry weather occurs or until harvest time.
Diseases are evident in stored peanuts also. The best example of this is a disease called yellow mold
which produces aflatoxin in stored peanuts.

Most peanut diseases occurring in Florida are caused by fungi. In addition, four viruses (peanut
mottle, peanut stunt, peanut stripe and tomato spotted wilt) have been identified in Florida. Peanut
stripe virus was first found in Florida at University of Florida plant breeding sites in 1983. Tomato
spotted wilt virus (TSWV) was first found in commercial peanuts in 1986 in Santa Rosa county. TSWV
has the potential for limiting yield. Some fields have had incidences of TSWV greater than 50%.

Pathogens can live on or in a peanut plant and most of them are capable of surviving in association
with the soil. In order to understand this complex ability of pathogens, we must know something about
their life cycles (SEE TABLE 3.)

FUNGI are organisms that do not have true roots, leaves, stems or chlorophyll. Instead, they have
hyphae (microscopic threads) of various types which can grow in the soil or in a host plant. Some fungi
do not have true hyphae; they have plasmodia and these are technically not fungi in the newest
taxonomic classification schemes. The water mold organisms, such as Pythium spp., are no longer
classified as true fungi. Some fungi, such as the peanut rust pathogen are obligate parasites and grow
and reproduce in the plant but not in soil. Hyphae absorb food from the plant or organic material in the
soil. Fungi derive their nourishment from plants or organic matter in the soil derived from the rotting
of old plant tissues.

Fungi reproduce by producing various types of microscopic spores. Some types of spores can be
spread by air currents; some types of spores require water for spread to occur. The fungi that cause leaf
spots and rust produce hundreds and even thousands of these spores in one spot on a leaf over a period
of time. Many of the fungi that cause pod rots, seedling blights, and root rots produce resting spores or
sclerotia (hyphal aggregates) that can survive in the soil for many years. Parasitic fungi in the soil
decline in number when their favorite hosts are absent. This is the basis for crop rotation as a
recommended disease control measure.
When parasitic fungi come into contact with a peanut plant, they grow on it and eventually enter
the plant. Some are able to penetrate directly, while others gain entrance only when an opening or a
wound is present. Plants have natural openings through which fungi enter into the plant. Diseases of
the roots and pods are more severe after being wounded by nematodes, insects or tillage equipment.
Therefore, one method of reducing disease is by controlling nematodes and insects.

Fungi, like other living things, are injured or killed by certain chemicals. This is the basis for
controlling leaf spots and rust with fungicides.








Most VIRUSES that cause disease in peanut are particles made of a RNA core covered with a
protein coat. Tomato spotted wilt virus is more complex in structure. The small size of virus particles
requires an electron microscope to visualize their shape and size characteristics. Peanut mottle virus
and peanut stripe virus are seedborne and spread by aphids. Tomato spotted wilt virus is spread by
thrips and has a wide host range with some other crops and weeds being susceptible.

Diseases caused be bacteria have not occurred in Florida. In some other countries in Africa and
Asia, bacterial wilt, caused by Ralstonia solanacearum,is a major problem.

With this basic information at hand, it becomes understandable that no one control measure will
be totally effective in controlling all peanut diseases. A series of coordinated control measures is
necessary to do a proper job. Each step requires knowledge and experience.

SEQUENTIAL CONTROL PRACTICES FOR PEANUT DISEASES

STEP 1. CROP ROTATION

Whenever possible, an interval of 3 4 years between peanut crops on the same land is preferable.
Shorter intervals increase the occurrence of most peanut diseases. For example, in one situation, peanut
leaf spot was 12 times more severe in June when peanuts were planted in a field which had peanuts the
previous year than in another field nearby where peanuts followed soybeans. From this do not presume
that a soybean-peanut rotation is best. Soybeans are highly susceptible to the fungus causing white mold
(Southern stem rot) in peanuts. Considering all diseases in peanuts, it is best to rotate with grass crops
such as pasture grasses, sorghum or corn, since many fungi causing diseases of grass crops do not cause
diseases of peanuts and vice versa. However, some fungi, such as Rhizoctonia solani can cause disease in
broadleaf and grass plant species. Rotation of peanut with Bahiagrass has been known for over 30 years
to be the best rotation for pest suppression and yield enhancement.

Recent studies demonstrated that the fungi that produce aflatoxin will be in higher populations
with rotations including corn and peanuts and in lower populations with rotations including soybeans or
fallow. Also, the organism that causes Cylindrocladium black rot (CBR) can survive in Florida soils for
at least 5 years even with a Bahiagrass rotation.

STEP 2. SITE LOCATION

If possible, do not locate the peanut field next to a field that had peanuts the previous year. Peanut
leaf spot has been more severe along edges of fields next to an old planting site. Other pests may be
reduced also by use of this method. Space fields of tomatoes, peppers or other vegetables and peanuts as
far from each other as possible to reduce spread of tomato spotted wilt virus by thrips from crop to
crop.

STEP 3. DEEP PLOWING, LAND PREPARATION, AND STRIP TILLAGE.

When turning the soil during land preparation, every effort should be made to bury surface trash
and stubble 6 inches deep even if a grass crop preceded the peanut crop. This method of control is
specifically aimed at reducing white mold and other soilborne diseases, but it is also beneficial in
reducing leaf spot when the interval between peanut crops is only one or two years.

Final land preparations, except for the finished seed bed and herbicide incorporations, should be
completed 3 4 weeks prior to planting, if possible. This period of time allows previous plant materials
to decompose, and therefore, be less likely to serve as a substrate for fungi such as Rhizoctonia solani
Meanwhile, beneficial microflora increase in the soil on the decomposing organic matter.


2








Planting peanuts in a minimum- or no-till situation has resulted in both good and bad results by
the same grower. Seedlings and young plants are highly susceptible to soilborne fungi such as
Rhizoctonia solani and Pythium spp. Poor stands resulted when the grower used a single disk opener for
the seed furrow. A better stand resulted when the grower used a subsoiler with the single disk opener.
The shank of the subsoiler cleared away organic matter from the emergence zone. This suggests that
pushing away some of the organic trash away from immediate planting zone could be beneficial.

Strip tillage, where the planting-zone only is cultivated with a rolling basket, tines, or some other
narrow tillage device, is becoming more popular. Usually a small grain such as wheat or rye is the
preceding crop. Surprisingly, soilborne diseases have not become a consistent, major problem in strip-
tillage systems except where rotation intervals have been reduced. Also, in strip-tillage systems
populations of thrips and tomato spotted wilt virus have been reduced.

STEP 4. LIME AND FERTILIZER RELATIONS WITH PEANUT DISEASES.

Calcium availability and placement are critical for improved quality and yields of peanuts.
Deficiency of calcium in the fruit predisposes the plant to peg and pod rots caused by fungi. Calcium
(Ca++) deficiencies (pops, black plumule in seed and reduced pod formation) usually result from
inadequate calcium in the pegging zone or competition from excess cations such as potassium (K+),
magnesium (Mg++) or ammonium (NH4+). Gypsum (landplaster) can replenish calcium in the pegging
zone. Avoid excessive use of potassium on peanuts. Blemished pods (nonbright) are commonly
colonized by Rhizoctonia solani and other fungi because calcium is limiting in the pegging zone. Use a
limestone source without magnesium if magnesium is adequate according to soil tests. Virginia-type
peanuts have a higher calcium requirement than runner-types because of the larger pods produced by
Virginia-type peanuts. Pod rot caused by fungi other than Sclerotium rolfsii (white mold) and
Cylindrocladiumparasiticum (CBR) is best reduced by use of lime prior to planting coupled with an
application of gypsum at early pegging.

For runner peanuts, the soil in the pegging zone should have at least 250 ppm of Calcium. When
Virginia-type peanuts are grown, 800 lb/A of gypsum should be applied at earliest pegging. Add 400
lb/A of gypsum for other peanut types. Addition of 440 lbs/A of gypsum has reduced the invasion of
peanuts by fungi (e.g. Aspergillusflavus) that produce aflatoxin. The rates of gypsum mentioned herein
relate to bagged gypsum applied as a 18 inch band in the pegging zone as a standard. With bulk
formulations of gypsum (e.g. phosphogypsum), doubling the rate of the bulk material should attain
nearly the same rate.

STEP 5. WEED CONTROL.

Less white mold and other soilborne diseases can occur where herbicides are used rather than
cultivation for weed control. Cultivation frequently increases damage to plants and often results in soil
and debris being deposited on the peanut plant. These conditions are ideal for development of white
mold and other soilborne diseases. Caution must be used with herbicides as intensive use of them will
stress plants and reduce SMK's. Cultivation in row middles prior to root growth in that zone is not
expected to increase disease.

Leaf spot and rust will be more difficult to control where weeds are present. Weeds interfere with
spray deposition and allow leaf wetness periods to be extended. Peanut leaf spot has been observed to be
more severe under coffeeweeds while non weed areas had less peanut leaf spot. Such a situation may not
be considered important until spray intervals are interrupted or a less effective fungicide is used. Spores
produced near the weeds serve as an intense source of inoculum, thereby off-setting desired control.


3






STEP 6. NEMATODE CONTROL.


Nematodes cause wounds in roots and pods. They create an open door situation for fungi. Pod rot
and white mold can be suppressed by reducing damage from nematodes. However, the degree of white
mold reduction may not be enough to eliminate the use of other tactics for white mold.

STEP 7. USE OF HIGH QUALITY SEED.

Purchase high germinating seed with high vigor. This will aid in reducing seedling diseases caused
by fungi. Also, a thicker stand of peanuts is likely to have a lower incidence of tomato spotted wilt virus
when compared to thicker stands in the southeastern United States. In Texas, thinner stands have not
been shown to be associated with increased incidences of tomato spotted wilt virus.

STEP 8. SEED TREATMENT, EARLY SEASON USE OF INSECTICIDES, AND STAND
ESTABLISHMENT.

Most of the seed peanuts that you buy are treated with a fungicide seed treatment. This control
measure increases the original stand by reducing seed and seedling decay caused by fungi. We have
measured beneficial effects of seed treatments up to 14 days after planting using seed treatment
chemicals. Thicker stands reduce tomato spotted wilt virus. Do not offset benefits from seed treatment
by planting excessively deep or too early in the spring when soils are cool. This is particularly important
with seed of the Southern Runner variety or other small-seeded varieties. Also, read step 2.

The following seed treatment fungicides are effective and are available in combinations to control
the array of fungi that cause seedling blight in peanuts.
Apron 2.65FL or 50W or XL LS
Captan (many formulations)
Thiram
PCNB (Terraclor)
Vitavax (use in combination with Thiram, Captan, or PCNB, e.g. Vitavax PC)
Gustafson 4 Way (Preorder necessary)
Allegiance FL

Lorsban 4E applied at 2 qts/A in a 10" band over the row prior to emergence of planted peanuts
has directly reduced seedling blight caused by Rhizoctonia solani and increased yield. Thimet 20G used
in-furrow, at 5.5 oz/ 1000 ft-of-row (max. is 7.5#/acre) has reduced the incidence of tomato spotted wilt
virus.

CAUTION: DO NOT FEED TREATED SEED TO MAN OR BEAST UNDER ANY
CIRCUMSTANCE.


4






STEP 9. RESISTANT VARIETIES.


Some varieties have intermediate levels of resistance to diseases. Where resistance to leaf spot
exists, fewer applications of fungicides may be used. Large seeded peanut varieties require higher levels
of calcium in the pegging zone because they are more susceptible to some pod-rotting fungi. Table 1
provides a list of some varieties with their reactions to some diseases.


Table 1. Reactions of Peanut Varieties to Different Diseases


DISEASE

VARIETY* Early Late leaf White Tomato spotted
leaf spot spot CBR mold wilt virus Aflatoxin Rust Limb rot

Florunner +/-

Virugard +

Sunrunner*

Marc I*

Andru 93

Southern Runner + + + + +/- +

GK 7* -+/-

Georgia Runner*

Georgia Green + +/- + +/-

Georgia Bold* +/-

C-99R + +/- + ++ +

Gregory +/- ? + ?

Sun Oleic 95R* highly susceptible

Sun Oleic 97R +/-

AT 108

AT 120

NC 7 +/- +/-

NC 9 +/- +/

NC-V11 +/- +/-

NC 12C +/- +/

Florida MDR98* ..** -

Florigiant*

AT 201 +

VC 1* +/-

Coan (see footnote below) highly susceptible

Perry +/-

Tamspan 90

Tamrun 96 +/- +

Tamrun 98 Table 1 cont'd


5






















































STEP 10. ADJUSTING PLANTING DATE.

Earlier planting reduces the impact of peanut leaf spot provided a proper spray schedule is used.
For example, peanuts planted in early to mid April may not have to be sprayed with fungicides until
they are 60 days old compared to 25-35 days after planting for peanuts planted during mid May to early
June. However, if crop rotation is not used and a wet and warm spring occurs, delaying the initiation of
spraying for such early planting could result in severe leaf spot.

Tomato spotted wilt virus (TSWV) is spread by thrips. Populations of thrips are somewhat lower
during May. Therefore, planting early to reduce leaf spot may result in more TSWV than if planting is
done in May. Also, planting too early into cool soils may result in more seedling blight. Higher seeding
rates should be used for planting in April, particularly in the panhandle of Florida, to compensate for
plants lost to seedling blight.

Later plantings of peanuts have resulted in reduced levels of CBR in other states. This effect has
not been documented in Florida. Later plantings have resulted in higher levels of aflatoxin in
association with more lesser corn stalk borers in some tests in Alabama.


6


Disease
Early Late leaf CBR White Tomato spotted Aflatoxin Rust Limb rot
Variety Table 1 continued leaf spot spot mold wilt virus

Georgia Hi-OL +

VA C92R +

VC 2 +

Hull + + + + +

AT 1-1

Carver + + +

Andru II +/- + + ?

DP-1 + ? + + +

GP-1 +

Norden + +
GA 01R
+ + + ++
GA 02C
+ +
AP3
+ ++ ++

Large seeded varieties tend to be more susceptible to some pod-rotting fungi. Also, some Virginia-type peanuts are quite susceptible
to leaf spot. The variety Coan has resistance to root knot nematode.


Seed no longer available
++ Highly resistant
+ Some resistance
- No known resistance
+/- May have some resistance if disease pressure is not high
S Susceptible









STEP 11. AVOID DEEP PLANTING IF MOISTURE PERMITS.


Planting excessively deep will offset benefits from seed treatments. The longer it takes for a
seedling to emerge, the longer the entire plant is exposed to soilborne fungi. Recommended planting
depths are 2 to 3 inches in light textured soils and 1 1/2 to 2 inches in heavy-textured soils. The
avoidance of deep planting is particularly important for small-seeded varieties such as Southern Runner
and for establishing thick stands to reduce tomato spotted wilt virus.

STEP 12. MINIMIZE STRESS ON THE ROOT SYSTEM.

Excessive use of herbicides and excessive wetting or drying of soils can weaken the root system and
reduce the rate of root growth, thereby allowing "weak" fungi to colonize root tissue and reduce plant
vigor.

STEP 13. FOLIAR APPLICATIONS OF FUNGICIDES.

Foliar applications of fungicides are directed primarily at peanut leaf spot and peanut rust.
However, certain soilborne diseases, such as white mold, cylindrocladium black rot (CBR) and limb rot
are suppressed with some foliar sprays. Sprays with Folicur 3.6 F or Abound 2.09 F will suppress limb
rot, white mold and cylindrocladium black rot. Sprays with Moncut will suppress white mold and limb
rot. Sulfur that is added to sprays of chlorothalonil or mancozeb is helpful in reducing rust and, to some
extent, leaf spot.

Fungicides do not eradicate established disease; they protect uninfected tissue from becoming infected.
For this reason, your spray program should begin before disease appears. Table 2 summarizes the
effects of some fungicides against some diseases.

Table 2. General summary of effectiveness of some foliar fungicides against various diseases.

Headline
Disease Abound Chlorothalonil Copper Mancozeb Topsin Folicur Moncut Strateg Rovral
fungicides M o

White mold ++ ++ ++

CBR + + +

Limb Rot ++ + -+ + + ++ +

Crown rot ++ +
(A. niger)

Diplodia +
crown rot

Rhizoctoni + + + +
a pod rot

Pythium
root & pod ?
rot

Leaf spot + ++ + + + ++ +

Rust' + ++ + ++ +

1 Sulfur will suppress leaf spot and rust.


7






A. INITIATION OF SPRAY PROGRAM FOR LEAF SPOT WITHOUT USE OF FORECASTING.
--At the present time, no specific date can be given to start a spray program. However, certain
guidelines should be helpful. Also, see Plant Protection Pointer No. 19 for determining the level of leaf
spot in your field as it relates to yield. PPP No. 19 is useful for highly susceptible varieties.

1. Beginning at 30 days after planting or when night temperatures become 65F or more,
periodically walk through a representative portion of your peanut fields looking for a trace
amount of peanut leaf spot. Early detection in conjunction with early spraying will make
subsequent fungicide applications more effective. Greater specificity on this point are presented
in footnote 1 of Table 4.

2. Leaf spot will appear earlier when peanuts are not rotated with other crops. Double cropping is
not considered an adequate rotation time interval.

3. Dry weather will retard leaf spot development. Conversely, wet weather aids leaf spot
development.

4. Where a large acreage is involved and the fungicide is applied by ground equipment, begin your
spray program early enough so that the entire acreage has been sprayed before leaf spot begins on
the last part of the acreage sprayed. This is a judgement decision on your part based on your own
past experience for those fields involved.

5. Peanuts planted prior to mid April will be exposed for a shorter period of time to leaf spot-
favorable weather than peanuts planted at later dates (assuming the same age at harvest).

6 Peanut fields or those portions of a field next to a field planted in peanuts the previous year should
be sprayed by the time they are 35 days old. It is common to see leaf spot begin on edges of fields
next to a previous peanut crop.

B. REQUIREMENTS FOR USE OF A FORECASTING SYSTEM IN FLORIDA FOR
OPTIMIZATION OF SPRAY TIMING FOR PEANUT LEAF SPOT

Because leaf wetness is necessary for the leaf spot fungi to infect peanuts, the use of a forecasting
system based upon the number of days with rain or irrigation could be useful in optimizing spray
timing. IN "DRY" YEARS, THE NUMBER OF SPRAY APPLICATIONS CAN BE REDUCED BUT
IN "WET" YEARS, MORE SPRAY APPLICATIONS MAY BE NECESSARY TO MINIMIZE THE
PROGRESSIVE LOSS OF YIELD WITH CORRESPONDING INCREASES IN LEAF SPOT.

Several forecasting systems for peanut leaf spot have been tried or are in use. The system that
currently has appeal for Florida is one based upon AU-Pnuts, a model developed at Auburn University.
It is relatively simple to use and requires that the growers utilize a rain gauge, pay attention to weather
forecasts and record moisture events on a daily basis. Four years of data as of 1992 with this system in
Florida have proven that this system is reliable.

Collection of moisture data (events) for spray program decisions

Observing and recording occurrences of leaf wetness are necessary to successful forecasting of peanut
leaf spot. These occurrences of leaf wetness will be referred to as moisture events.

A DAILY MOISTURE EVENT INCLUDES:
1) A DAY WITH RAIN OF 0.1" or MORE, OR
2) A DAY WITH IRRIGATION OF 0.1" or MORE, OR
3) A DAY (night) WHERE FOG OR DEW BEGINS BY 8:00 PM.

If, for example a peanut field received 1" of irrigation one day and then received 0.1" of rain the next
day and then 0.3" inch on the third day and a fog occurred all night on the fourth day, four moisture
events have occurred. Moisture events do not have to occur in consecutive days to be counted.


8







Requirements for initiation of the spray program


Begin recording daily moisture events as described above on May 1 for peanuts that emerged by May
1. If emergence occurs after May 1, begin recording moisture events as soon as emergence occurs. May
1 has been chosen because at that time, temperatures are likely to be at or near those favorable for
infection and disease progress. Fields separated from each other or areas within large fields that might
receive different amounts of rainfall or irrigation will require collection of separate moisture data.

Make your first spray application on emerged peanuts if:
1) 6 or more days with moisture events have been recorded since May 1 (or since date of emergence
for later-planted peanuts)
OR
2) 5 days with moisture events have been recorded since May 1 (or since date of emergence for later-
planted peanuts) and the average probability* for rain for the next five days is 40% or more
OR
3) 4 days with moisture events have been recorded since May 1 (or since date of emergence for later-
planted peanuts) and the average probability* for rain for the next five days is 50% or more.

* EXAMPLE: To calculate average probability for the next five days:

May 7= 50% chance for rain
May 8= 70% chance for rain
May 9= 80% chance for rain
May 10= 30% chance for rain
May 11=+ 30% chance for rain
260
260 .5 = 52% Therefore the average probability for the next five days is 52%.

Requirements for determining spray intervals with forecasting

Beginning on the 10th day after the previous spray application, record the days that have a moisture
event as described above for initiating the spray program. Apply the next spray 10 days or later after
the previous spray as soon as one of the following situational patterns for moisture events and rain
probabilities occur:

Spray when any one of the four options below has been satisfied:

OPTION 1
ten (10) days or more have elapsed since the previous spray AND
no rain has occurred since the 10th day BUT
the average probability for rain for the next five (5) days is 50% or more

OPTION 2
ten (10) days or more have elapsed since the previous spray AND
one day had a moisture event since the 10th day AND
the average probability for rain for the next five (5) days is 40% or more

OPTION 3
ten (10) days or more have elapsed since the previous spray AND
two days had a moisture event since the 10th day AND
the average probability for rain for the next five (5) days is 20% or more

OPTION 4
ten (10) days or more have elapsed since the previous spray AND
at least three (3) days had a moisture event since the 10th day

A spray application should be made as soon as possible after your data indicate that a spray is needed.


9




C. Spray Intervals without use of forecasting. -- An average spray interval for fungicide applications
should be 10 14 days for the susceptible varieties (See Table 1). If a Virginia-type peanut is planted, a
10 day spray interval is advised. During dry periods, the longer interval is more suitable, but during
periods of heavy rains, the shorter interval should be used because rains promote disease development
and wash off spray residues. Spray intervals longer than 14 days should not be used on susceptible
varieties (See Table 1). With varieties such as C99R, DP-1, Hull, and Southern Runner, 20-day spray
intervals are adequate.

If you normally make 7 applications/season, better leaf spot control will result if the first 4
applications are 10 days apart and the last 3 applications are 14 days apart rather than a switch from 14
to 10. Growers often shorten spray intervals when it is too late. If leaf spot is severe in mid season
because of poor control practices earlier, then use 7-10 day intervals at highest label rates. Also, cool
spring weather that delays crop growth may require more vigorous spray programs from mid-late
season.

D. Applications of Fungicides.--Fungicide sprays may be applied by ground equipment or by
aircraft. Ground equipment includes, boom sprayers and air-assisted sprayers. Fungicides will perform
slightly better when applied at 10-15 gallons of water per acre if a high psi (250) is used. For low psi
situations (40-50 psi), 25 gallons of water per acre is best. Using 50 GPA at 250 psi will perform well
provided heavy rains do not occur. However, over the years, use of 20-30 gallons of water per acre will
result in best control, regardless of spray pressure. When using boom equipment, be sure that one
nozzle is centered directly over the row center. Where additional nozzles are used/row, swivel nozzles
are available and will allow you to direct the spray as your crop grows. With fungicides, spraying with a
single flat fan nozzle over the center 20" band of the row using the broadcast rate in the spray band is
legal and has been extremely effective in my tests for control of white mold, leaf spot, and rust.

Hollow cone or flat fan nozzles are equally effective for control of peanut leaf spot. Various sizes of
nozzle parts are available for adjusting to different gallonages and pressures. Consult with an
equipment dealer about sizes you need for various gallonage-pressure combinations at a given tractor
speed. Use the same nozzle size for the entire boom.

Air-assisted sprayers would be expected to provide control equal to boom sprayers provided that the
nozzles are adjusted to deliver a uniform pattern of spray across the sprayed swath. Most failures with
air-assisted sprayers result from lack of uniform spray deposition across the entire spray swath or
attempts to over-extend the sprayer swath beyond spray design specifications. Wind can cause uneven
distribution of spray deposition.

Irrigation equipment can be used to deliver the fungicide (fungigation) provided that the label of a
product allows such a use. First and foremost, this should not be attempted without anti-back siphoning
devices on the well and injection equipment and without label clearance of the fungicide. Residues of the
fungicide on the leaves are less when fungicides are injected through an irrigation system rather than a
conventional ground spray. Leaf spot control has not been as effective when using fungigation
compared to ground equipment in most tests in the southeastern U.S., particularly when the amount of
irrigation water is greater than 0.1" of water. Yield has been decreased when using fungigation
compared to ground spray applications in some tests while the reverse has resulted in other situations.
It is potentially dangerous to use.

Aerial application of fungicides has proven effective through many years of grower use. Any method
of application (ground or air) will perform well if other practices such as early planting, early initiation
of a spray program, and proper spray intervals are used to minimize disease early in the season. The
cost of using aerial application versus ground equipment is defendant upon the acreage involved, cost of
maintaining equipment, labor costs and life expectancy of equipment. The grower should consider all
these factors in relation to his own enterprise. Aerial applications are generally applied with 3-7 gallons
of water per acre. Experience indicates that better leaf spot control occurred with 5 gallons than with 3
gallons per acre. Less wind occurs during the early part of the day and thus, better spray deposition
occurs on the peanut plant during calm times of the day.


10







E. Alternation of fungicides. Alternation of fungicides can serve three purposes. First, a grower may
chose to reduce cost by using a more inexpensive product alternatively with a more expensive product
for control of a disease. This strategy is used by some to reduce costs associated with control of peanut
leaf spot. If the two products are equally effective for control of disease, the ordinal usage of the
products does not matter. However, if one product is clearly more effective than another, the more
effective product should be used earliest in the season to minimize early buildup of inoculum. For
example, if mancozeb or copper fungicides are used alternatively with chlorothalonil for control of
peanut leaf spot, use chlorothalonil during the earliest sprays.

A second purpose of alternating fungicides is to delay the onset of resistance within the target pathogen
to a fungicide with a specific mode of action. For peanuts, Abound, Headline, Topsin M, Folicur and
Tilt are labeled and possess specific modes of action against the target fungi. The development of
resistance by the pathogen can be delayed or offset if the specific mode of action chemical is not allowed
exclusive exposure to the pathogen. If the specific mode of action fungicide is tank-mixed or alternated
with a broad spectrum fungicide, like chlorothalonil or mancozeb, the onset of resistance is at least
delayed.

A third purpose of alternating fungicides is to accommodate the control of more than one disease
when more than one fungicide is required to suppress multiple diseases. Currently, various sequential
schedules using chlorothalonil alternated with Folicur or Abound are possible to control leaf spot, rust,
and white mold. Moncut can be substituted for Folicur or Abound for control of white mold. Moncut is
not effective against leaf spot, rust, or cylindrocladium black rot (CBR). Usually, the spraying of two
chlorothalonil sprays followed by four applications of Folicur is a good spray program for controlling
leaf spot, white mold, and cylindrocladium black rot. See Table 2 for determining the effectiveness of
various fungicides against different fungal diseases.

F. Cessation of spray program.--Continue the spray program up to 14 days prior to your anticipated
date of digging. Foliar fungicides labelled on peanut should not be applied within 14 days of harvest
except for copper-containing fungicides. If a possibility exists that a long term rain pattern is likely to
occur from a hurricane or low pressure weather system, you may need to delay your digging date and
apply a foliar fungicide.

G. Fungicides for leaf spot, rust, limb rot, white mold and cylindrocladium black rot (CBR). --Table 4.

STEP 14. CHEMICAL CONTROL OF WHITE MOLD.

Folicur 3.6F is labelled for use on peanuts to control white mold, leaf spot, CBR, rust and limb rot.
Rates up to 7.2 fl.oz. per acre should be used. Three or four applications, spaced 12-14 days apart,
should be used beginning 45 days after planting for CBR. For white mold, Folicur 3.6 F Abound 2.08 F,
and Moncut 70 DF can be alternated during the mid portion of the season. Headline 2.09 F can be
substituted for Abound in the rotation.

Abound 2.08 FL and Headline 2.09 are labelled for control of white mold, limb rot, and leaf spot. A
limit of two applications/crop is allowed for Abound at 18.5 24.6 fl.ozs./acre. For Headline 2.09 F,
three applications/crop are allowed at a maximum of 15 fl ozs./acre.. Do not apply within 14 days (40
days for Moncut) of harvest. Alternating Abound or Headline with Folicur or Moncut has been
particularly effective for white mold. Abound has some activity against CBR.

Moncut 70 DF can be sprayed to control white mold. With ground equipment, apply 2-4 lbs/A at 60-70
days after planting or 2 lbs/A at 60 days after planting followed by a second application of 2 lbs/A at 90 days
after planting. If limb rot is also present, the use of a broadcast application may be best. Moncut can be
applied via aerial application or chemigation but a directed band spray with ground application is likely to be
best. Moncut can be tank mixed with chlorothalonil.

When using Folicur, Abound, or Moncut for suppression of white mold apply them in a 20" band along
the center of the row. If suppression of limb rot is needed, use a broadcast application.


11







Use of an early pegging time (45-60 days after planting) treatment of Lorsban 15G has suppressed white
mold and increased yields. It has added benefits because it is reasonable in cost and is effective for lesser corn
stalk borer control. The rate for Lorsban 15G is 15 oz./1000 foot of row (13.3 lb./A for 36" row centers).
Apply Lorsban in a 6 to 12 inch band centered on the row. Do not make more than 1 application/year or use
within 21 days of harvest. See label for restrictions. Do not apply to wet foliage. Do not throw dirt on the
base of the plant when cultivating. Do not incorporate granules into the soil as the white mold fungus is active
at the soil surface and that is where the granules need to be placed.

STEP 15. CONTROL OF CYLINDROCLADIUM BLACK ROT (CBR)

At the present time, CBR is difficult to control. The varieties Hull, C99R, Carver, NC 12C, Southern
Runner, Georgia Green, GA 01R, GA 02C, and AP3 have small levels of resistance to CBR compared to
Florunnner. Preplant fumigation with metam sodium-containing products (Vapam) or chloropicrin has been
used somewhat successfully in North Carolina, Virginia, and Georgia.

CBR has been suppressed in field tests with sprays of Folicur 3.6 F. Three or four sprays of Folicur
spaced 14 days apart, beginning when the peanuts are 45 days old, have reduced CBR. The spray program
with Folicur 3.6 F for suppression of white mold would be advantageous for suppression of CBR. Recently, we
have acquired some suppression of CBR with Abound 2.08 F.

STEP 16. CONTROL OF YELLOW MOLD ASPERGILLUSS FLA VS) OR SEGREGATION III
PEANUTS.

Infection by this fungus takes place either before or after digging when the moisture content of the peanut
is between 12-35 percent. Inverting allows the peanuts to dry faster and minimizes contact of the soil with the
fruit. More aflatoxin can be expected in association with drier soils. Also, control pod rot, soil insects and
nematodes.

Once the peanuts are combined every effort should be made to dry the peanuts below 12% moisture as
soon as possible. Do not allow a wagon full of peanuts to stand without proper drying. Corn and peanuts are
the crops most likely to increase populations of this fungus.

For more complete information on peanut harvesting, drying an storage, see University of Florida Agricultural Engineering Bulletin
209.


12








TABLE 3. DISEASES OF PEANUT FOUND IN FLORIDA


ORGANISM


Peanut mottle virus



Peanut stunt virus


Peanut stripe virus

Tomato spotted wilt virus


Pythium spp.


Rhizoctonia solani





Fusarium spp.



Aspergillus niger


Aspergillus flavus


DISEASES or SYMPTOMS


Mosaic
(sometimes symptomless)


Plant Stunting and
Fruit Distorting

Mosaics & Stripes

Stunting, ring spots,
mottling and mosaic

Seedling Blight, Root
Rot, Peg Rot, Pod Rot.

Seedling Blight, Stem Rot,
Root Rot, Peg Rot, Pod Rot,
Aerial Leaf Blight, Limb
Rot or Leaf spot

Associated with tissue, but
causation of disease
has not been established

Seedling Blight, Early
Season Crown Rot.

Seedling Blight, Yellow
Mold (Cause of Seg. Ill
Peanuts).


TYPE OF CARRIED
ORGANISM IN SEED


Virus



Virus

Virus

Virus


Fungus


Fungus






Fungus


Fungus


Fungus


++


SURVIVES IN
SOIL OR WITH
PLANT DEBRIS


DISSEMINATED BY
AIR CURRENTS OR
RAIN SPLASH


Aphid-Transmitted


++

++


++




++


++


++


++


++


++


Aphid-Transmitted

Aphid-Transmitted

Thrips-Transmitted


Rain splash


+


+


++


+


Table 3 continued on next page


13








TABLE 3. (Continued)


ORGANISM DISEASES or SYMPTOMS

Rhizopus sp. Seedling Blight.

Macrophominia phaseolina Seedling Blight, Peg Rot,
Pod Rot, Root Rot, Stem
Rot.


Sclerotium rolfsii Stem Rot (White Mold),
Pod Rot, Peg Rot.

Cercospora arachidicola Early Leaf spot

Cercosporidium personatum Late Leaf spot, Stem
Spot, Peg Spot

Puccinia arachidis Rust

Leptosphaerulina crassiasca Leaf Scorch

Alternaria sp. (rare) Alternaria Leaf spot

Cylindrocladium parasiticum Peg Rot, Pod Rot, Root
(Calonectria ilicicola) Rot, Stem Rot (CBR)

Lasiodiplodia sp. Stem Rot, crown rot

Ascochyta sp. (Phoma) Leaf spot and Blotch

Neocosmospora sp. Root & pod rot, wilt

++ Occurs commonly.
+ Occurs.
-- Not regarded as a source.


TYPE OF
ORGANISM

Fungus

Fungus


Fungus



Fungus

Fungus



Fungus

Fungus

Fungus

Fungus


Fungus

Fungus

Fungus


CARRIED
IN SEED

++

+


+


SURVIVES IN
SOIL OR WITH
PLANT DEBRIS

++

++


DISSEMINATED BY
AIR CURRENTS OR
RAIN SPLASH

+


++


++

++


++

++



++

++

++


++

++

++


++


+


+


+

+


+


+

+


14





TABLE 4. FUNGICIDES FOR SUPPRESSING PEANUT DISEASES


DISEASES MAXIMUM REENTRY INTERVAL
FUNGICIDE1 CONTROLLED RATE/ACRE2 LIMITATIONS DAYS

12 hrs or 7 days depending
Do not apply within 14 days of upon availability of eye
harvest. Do not graze or feed treated flush equipment &
Equus 720 or Echo 720 or 6 FLs Leaf spot & rust 1 1/2 pts. vines, hay or hulls to livestock education of farm workers.

Do not apply within 14 days of
harvest. Do not use treated crop for
Bravo Weather Stik 6 FL Leaf spot & rust 1 1/2 pts. livestock feed. Same as Equus

Echo 90 DF Leaf spot & rust 1.2 lbs. Same as Equus Same as Equus
1 day or 7 days depending
Champion 77 WP, Kocide 101 on availability of eye flush
77WP, Kocide 61.4 DF, or Basicop No time limitations except reentry containers & education of
53 WP Leaf spot 3 lbs. limitations farm workers.

Champ 57.6 DP Leaf spot 2 lbs. Same as Champion 77 WP Same as Champion 77 WP

Kocide 4.5 LF or Champ Formula 2 pts. Same as Champion 77 WP
2 FL Leaf spot Same as Champion 77 WP
Dithane 75 DF Rainshield, Dithane
M-45 WP, Manzate 75 DF, Do not apply within 14 days of
Penncozeb 80 WP, Penncozeb 75 harvest or graze or feed vines to 1
DF, or Manzate 80 WP Leaf spot & rust 2 lbs. livestock. Limit is 12.8 lbs. a.i./crop.

Bravo Ultrex 82.5 WDG Leaf spot & rust 1.4 lbs. Same as Equus Same as Equus

No time limitation except renentry 1
Cuprofix Disperss 36.9 WP Leaf spot 4 lbs. limitations

No time limitations except reentry
Kocide 2000 53.8 DF Leaf spot 2 / lbs. limitations Same as Champion 77 WP

No time limitations except reentry 12 hrs.
Ten Cop 5E Leaf spot 4 pts. limitations

Dithane F45, Penncozeb or Manex Same as Dithane 75DF 1
II 4 FLs Leaf spot &rust 1.6 qts. Limit is 12.8 qts./crop

Bravo S Leaf spot & rust 4 1/2 pts. Same as Equus Same as Equus

2.86 lbs. if one appl./ 12 hrs.
crop is used or 1.43
lbs. if 2 appl./crop is 2.86 lbs. limit/crop. Do not apply
Moncut 70 DF White mold & limb rot used. within 40 days of harvest.


Table 4 continued


15







DISEASES MAXIMUM REENTRY INTERVAL
FUNGICIDE1 CONTROLLED RATE/ACRE2 LIMITATIONS DAYS
Table 4 continued Do not apply within 14 days of
1 twin pack treats harvest. Limit is 16 fl ozs./A. Do not
Tilt/Bravo Leaf spot 10 acres use treated crop for livestock feed. 2

Sulfur3 Table Rust & leaf spot 1 qt. See label. 1

Do not apply more than 16 fl.ozs. per
crop. Do not apply within 14 days of
harvest. Do not use treated vines or
Tilt 3.6E4 Leaf spot 4 fl. ozs nuts for livestock feed.

Folicur 3.6 F Leaf spot, rust, CBR, white Limits are 28.8 fl. ozs./crop and up to 12 hrs
mold 7.2 fl ozs. 14 days before harvest

Limit is 2 applications or 1.54
qts.A/year. Do not apply within 14
White mold, leaf spot, rust days of harvest. Do not use treated 4 hrs.
Aspergillus niger, CBR, & crop for livestock feed. Do not apply
Abound 2.08 FL4 Rhizoctonia diseases 24.6 fl. ozs. through irrigation system

Limit is 3 applications/crop or 45 fl 12 hrs.
ozs./crop. Do not apply within 14
days of harvest and do not graze or
Leaf spot, rust, white mold, harvest for forage use. Peanut meal
Headline 2.09 F4 Rhizoctonia diseases 15 fl. ozs. may be fed.

Limit is 6 appl./crop and do not 1
make more than 2 consecutive
applications. Do not apply within 14
Stratego 250 EC4 Leaf spot & rust 14 fl. ozs. days of harvest
Do not apply within 14 days of
Topsin 70 WP Leaf spot5 & Aspergillus harvest. Do not use treated crop for 12 hrs.
niger4 1/2 lb livestock feed.
1. Begin applications no later than at the first sign of disease. For varieties that mature earlier than Georgia Green, begin spray program when
peanuts are 25 days old but not earlier than the third week of May.
2. Rate/Acre is for a broadcast acre but the entire rate can be directed (directed spray) at the existing canopy even if vine coverage of ground is not
complete. With aerial application, broadcast rates are always applied in a broadcast manner. Rates below maximum rates can be used and are
often suggested on the label.
3. Addition of a flowable sulfur (1 qt/A) enhances control of leaf spot and aids in the control of rust. Trade names include: That, Microflo, Enduro,
Supersol, Sulfur 6L, Microthiol, Super Six and others. When rust appears shorten spray intervals so they do not exceed 10 days.
4. This product could become ineffective with continued use due to development of resistance by the fungal pathogens. To delay or offset such an
occurrence, this product should be used in conjunction with a broad spectrum fungicide such as chlorothalonil or mancozeb.
5. Resistance to Topsin exists.


16




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