• TABLE OF CONTENTS
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 Introduction
 Accurate diagnosis of diseases
 Monitoring pathogens
 Control action guidelines...
 Prevention and management...






Title: Florida plant disease management guide
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 Material Information
Title: Florida plant disease management guide
Alternate Title: Ornamentals and turf
Fruit and vegetables
General plant pathology, field crops and pasture grasses, fungicides, adjuvants and application techniques
Physical Description: v. : ; 28 cm.
Language: English
Creator: University of Florida -- Dept. of Plant Pathology
Florida Cooperative Extension Service
Publisher: The Extension
Place of Publication: Gainesville Fla
Frequency: annual
regular
 Subjects
Subject: Plant diseases -- Periodicals -- Florida   ( lcsh )
Pesticides -- Periodicals   ( lcsh )
 Notes
Statement of Responsibility: Plant Pathology Dept., University of Florida and Institute of Food and Agricultural Sciences, Florida Cooperative Extension, University of Florida.
Numbering Peculiarities: Issued in three volumes: v. 1, General plant pathology, field crops and pasture grasses, fungicides, adjuvants and application techniques; v. 2, Ornamentals and turf; v. 3, Fruit and vegetables.
General Note: Description based on: 1999-2000.
General Note: "SP-52"
 Record Information
Bibliographic ID: UF00053871
Volume ID: VID00002
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 44549741
lccn - 00229071
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Preceded by: Florida plant disease control guide

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Table of Contents
    Introduction
        Page 1
    Accurate diagnosis of diseases
        Page 2
    Monitoring pathogens
        Page 3
    Control action guidelines for diseases
        Page 3
    Prevention and management methods
        Page 4
        Page 5
        Page 6
        Page 7
Full Text




PP-193
UF UNIVERSITY of

UFLORIDA
IFAS Extension



Integrated Disease Management for Vegetable Crops in

FloridaI


Tim Momol, Jim Marois, Ken Pernezny and Steve Olson2


Introduction

A successful disease control program depends on
a crop production system which is closely aligned
with the goals of pest management. One must start
with the selection of appropriate varieties, an
irrigation system that minimizes leaf wetness, a
fertilizer program that results in optimum plant
growth, bed preparation, plant density, and canopy
management that affords optimum air circulation and
pesticide coverage when needed, a transplant program
which minimizes transplant shock, a clean seedling
production program, effective pest monitoring during
the season, and finally, a harvest and shipping
procedure which maximizes shelf life and produce
quality. Integrated pest management (IPM) as
applied to diseases of vegetables means using all the
tactics available to the grower (cultural, biological,
host-plant resistance, chemical) that provides
acceptable yield and quality at the least cost and is
compatible with the tenets of environmental
stewardship.


The five components of an IPM program are
prevention, monitoring, correct disease and pest
diagnosis, development and use of acceptable
thresholds, and optimum selection of management
tools. The management strategies available include
genetic control, cultural control, biological control,
and chemical control. What management strategy is
most relevant depends in part on the particular pest.
In general, weeds are most effectively controlled
with cultural and chemical practices. Diseases are
controlled most by host-plant resistance, cultural
practices, and chemicals. Insects and nematodes are
controlled with all four strategies.

For disease management, it is important to
understand the potential of a pathogen to infest and
spread in the crop. The three parameters of disease
progress are 1) the initial amount of inoculum, 2) the
rate of disease increase, and 3) the time the crop is
grown. These parameters interact in ways to produce
a rapid pathogen population increase, manifested as
exponential growth in many production systems
(Figure 1).


1. This document is Fact Sheet PP-193, one of a series of the Plant Pathology Department, Florida Cooperative Extension Service, Institute of Food and
Agricultural Sciences, University of Florida. Published November 2001. Revised December 2005. Please visit the EDIS Web site at http://edis.ifas.ufl.edu.
2. Tim Momol, associate professor, Plant Pathology Department; Jim Marois, professor, Plant Pathology Department, and Steve Olson, professor,
Horticultural Sciences Department, North Florida Research and Education Center, Quincy, FL; Ken Pernezny, professor, Plant Pathology Department,
Everglades Research and Education Center, Belle Glade, FL; Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences,
University of Florida, Gainesville, FL 32611.
The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the
products named, and references to them in this publication does not signify our approval to the exclusion of other products of suitable composition.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and
other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex,
sexual orientation, marital status, national origin, political opinions or affiliations. U.S. Department of Agriculture, Cooperative Extension Service,
University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry
Arrington, Dean







Integrated Disease Management for Vegetable Crops in Florida 2


Disease Increase Over Time
C 1
1
- 0.8
-o
S0.6

0.4

E 0.2
0
a 0
0 20 40 60
Days After Planting


Figure 1. Typical progress curve for polycyclic diseases.

The rate of disease increase over time is
dependent upon the interactions of the pathogen,
plant host, and the environment. For disease
management purposes, we are most concerned with
the interactions of the pathogen and host at the
population level of organization. However,
environmental conditions play a critical role in
determining the nature of plant disease epidemics. In
plant pathology, this set of interactions is known as
the disease triangle (Figure 2).

Understanding the biology of the pathogen,
host-pathogen interactions, and the effect of
environmental factors on this dynamic process in time
and space (disease epidemiology), is critical for
planning and implementing effective and efficient
management strategies. These strategies can affect
particular aspects of the growth of the pathogen
population. Host-plant resistance can affect all three
parameters by 1) reducing the amount of inoculum
via resistance to particular strains of the pest, 2) by
slowing the rate of pathogen buildup by reducing its
reproductive capacity, and 3) by reducing the total
period of exposure in short-season varieties.

Cultural control is aimed at reducing the primary
inoculum (sanitation) or reducing the rate of disease
increase by modifying the crop environment. A good
example of the latter is the use of drip irrigation
rather than overhead to reduce free water on foliage.
The total time that a crop is exposed to a pathogen
may be minimized by optimizing plant growth, thus
reducing the time to harvest. Biological control
usually affects the rate of pathogen buildup. Finally,


chemical control can affect the amount of inoculum
available at the beginning of the season (i.e. soil
fumigation) and/or reduce the rate of disease
development by killing a portion of the pathogen
involved in later stages of the epidemics.


Figure 2. Disease triangle.

Accurate Diagnosis of Diseases

Proper disease identification is critical for
making correct disease management decisions. This
will save time, money, and the environment.
Effective use of fungicides and other pesticides
depends on correct identification of the problem.

The accuracy of any diagnosis depends upon the
information supplied, the specimen material selected,
and the condition of the specimen when it arrives at a
clinic. Digital images of the fresh specimen with
symptoms and field-view images of the problem
might be useful in some cases. The Distance
Diagnostics and Identification System (DDIS),
available through the Florida Cooperative Extension
Service, may be used for this purpose in many
counties.

In order to apply disease management practices,
there should be knowledge of which pathogens are
present or are likely to appear in a particular field or
season. Descriptive and pictorial manuals are helpful
for identification of diseases commonly found in
Florida. It is important to know the common diseases
of a given crop specific to your area. Professional
scouting firms and the University of Florida
Extension Faculty can provide assistance in disease
diagnosis. Diagnosis can also be provided by sending


HOST


ENVIRONMENT


PEST






Integrated Disease Management for Vegetable Crops in Florida 3


samples to the Plant Disease Clinics of the University
of Florida located at Gainesville, Homestead,
Immokalee, and Quincy.

Monitoring Pathogens

As mentioned, monitoring is a critical
component of an effective IPM program. Monitoring
can be direct (looking for the pathogen or disease) or
indirect (recording environmental conditions which
affect disease development). Financial considerations
weigh heavily in the choice of monitoring practice.

Direct monitoring of diseases can be based on
symptoms or signs of the pathogen. Identification of
pathogens is generally difficult, because pathogens
usually are microscopic and can be detected typically
after the disease process has begun. Most monitoring
is actually for disease symptoms, with the control
strategy aimed at reducing further spread. Even when
visible symptoms are evident, levels of disease may
be so low as to make detection very difficult. To
optimize the chances of detection, one should
concentrate on those areas where disease is most
likely to occur, for example in low areas or areas of
lush growth. If this is not possible, an array of
sampling designs may be used, such as a diagonal
across the field, a random walk, a stratified design
where each subsection of the field is sampled, or a
stratified random design where a random sample is
taken in each subsection of the field (see UF/IFAS
Extension publication No. SP22 "Florida Tomato
Scouting Guide"). The appropriate sampling design
will depend on the level of disease expected, the
distribution of the disease and sampling schemes
already in place for other pests.

Disease distribution within a field is dependent,
in large part, on the source of inoculum for the
pathogen. If the disease is seedbore, in many cases
the first diseased plants will be more uniformly
distributed in the field. If the disease is soilbome, it
may often be found in clusters in the field. If it is
transmitted by insects, the distribution may be more
random, or a field edge effect may be apparent. Thus,
it is important to understand the biology of the
disease when developing an appropriate sampling
strategy for it.


Indirect monitoring of disease most often
involves stand-alone, turn-key computer systems with
probes or whole units in the field. Data commonly
gathered include temperature, relative humidity, and
leaf wetness. Data are typically recorded every 15
minutes, with data being used to update real time
indices of the likelihood of disease at a given time.
The algorithms for the models are often developed
from controlled environmental chamber experiments
where the minimum, maximum, and optimum
temperatures and relative humidity for fungal growth,
germination, and/or disease development are
identified. Leaf wetness, either monitored directly or
by prediction of dew point based on the relative
humidity and temperature conditions, is used if the
pathogen requires free water for germination. The
prediction of disease events through environmental
monitoring has been very successful in a few cases
and is used widely for those crops and diseases where
sufficient research exists.

For further information on scouting tomato
diseases, see UF/IFAS Extension publication No.
SP22, "Florida Tomato Scouting Guide". In
addition to identification keys, disease symptoms and
disease seasonality chart, mode of pathogen spread
and conditions that favor most diseases in Florida can
be found in this publication.

Control Action Guidelines for
Diseases

There are three major types of models used for
determining when a disease (or vector insect) may
exceed its economic threshold and a control action is
justified. The simplest is the critical point model,
where one parameter is monitored to determine if a
disease problem is likely to occur. Perhaps the best
known is the model of the corn flea beetle, which
transmits the bacterium that causes Stewart's wilt of
corn. In this pathosystem, the epidemic is dependent
upon the ability of the flea beetle vector to survive the
winter in the soil. This occurs in the northern U.S.
only during mild winters. By adding together the
average temperatures for December, January and
February, it is possible to predict beetle survival. If
the sum of the averages is less than 90, the threat of
Stewart's wilt is negligible. Between 90 and 95, the
threat is light to moderate. For values between 95 and






Integrated Disease Management for Vegetable Crops in Florida 3


samples to the Plant Disease Clinics of the University
of Florida located at Gainesville, Homestead,
Immokalee, and Quincy.

Monitoring Pathogens

As mentioned, monitoring is a critical
component of an effective IPM program. Monitoring
can be direct (looking for the pathogen or disease) or
indirect (recording environmental conditions which
affect disease development). Financial considerations
weigh heavily in the choice of monitoring practice.

Direct monitoring of diseases can be based on
symptoms or signs of the pathogen. Identification of
pathogens is generally difficult, because pathogens
usually are microscopic and can be detected typically
after the disease process has begun. Most monitoring
is actually for disease symptoms, with the control
strategy aimed at reducing further spread. Even when
visible symptoms are evident, levels of disease may
be so low as to make detection very difficult. To
optimize the chances of detection, one should
concentrate on those areas where disease is most
likely to occur, for example in low areas or areas of
lush growth. If this is not possible, an array of
sampling designs may be used, such as a diagonal
across the field, a random walk, a stratified design
where each subsection of the field is sampled, or a
stratified random design where a random sample is
taken in each subsection of the field (see UF/IFAS
Extension publication No. SP22 "Florida Tomato
Scouting Guide"). The appropriate sampling design
will depend on the level of disease expected, the
distribution of the disease and sampling schemes
already in place for other pests.

Disease distribution within a field is dependent,
in large part, on the source of inoculum for the
pathogen. If the disease is seedbore, in many cases
the first diseased plants will be more uniformly
distributed in the field. If the disease is soilbome, it
may often be found in clusters in the field. If it is
transmitted by insects, the distribution may be more
random, or a field edge effect may be apparent. Thus,
it is important to understand the biology of the
disease when developing an appropriate sampling
strategy for it.


Indirect monitoring of disease most often
involves stand-alone, turn-key computer systems with
probes or whole units in the field. Data commonly
gathered include temperature, relative humidity, and
leaf wetness. Data are typically recorded every 15
minutes, with data being used to update real time
indices of the likelihood of disease at a given time.
The algorithms for the models are often developed
from controlled environmental chamber experiments
where the minimum, maximum, and optimum
temperatures and relative humidity for fungal growth,
germination, and/or disease development are
identified. Leaf wetness, either monitored directly or
by prediction of dew point based on the relative
humidity and temperature conditions, is used if the
pathogen requires free water for germination. The
prediction of disease events through environmental
monitoring has been very successful in a few cases
and is used widely for those crops and diseases where
sufficient research exists.

For further information on scouting tomato
diseases, see UF/IFAS Extension publication No.
SP22, "Florida Tomato Scouting Guide". In
addition to identification keys, disease symptoms and
disease seasonality chart, mode of pathogen spread
and conditions that favor most diseases in Florida can
be found in this publication.

Control Action Guidelines for
Diseases

There are three major types of models used for
determining when a disease (or vector insect) may
exceed its economic threshold and a control action is
justified. The simplest is the critical point model,
where one parameter is monitored to determine if a
disease problem is likely to occur. Perhaps the best
known is the model of the corn flea beetle, which
transmits the bacterium that causes Stewart's wilt of
corn. In this pathosystem, the epidemic is dependent
upon the ability of the flea beetle vector to survive the
winter in the soil. This occurs in the northern U.S.
only during mild winters. By adding together the
average temperatures for December, January and
February, it is possible to predict beetle survival. If
the sum of the averages is less than 90, the threat of
Stewart's wilt is negligible. Between 90 and 95, the
threat is light to moderate. For values between 95 and






Integrated Disease Management for Vegetable Crops in Florida 4


100, the threat is moderate to severe. Above 100, the
threat is severe.

Although easy to apply, critical point models
often are inappropriate due to the complex nature of
many epidemics. The multiple point model is used to
address more complex pathosystems. These models
typically consider a number of parameters and assign
severity points to each, with the sum of severity
points indicating the potential need for control action.
These models are simple to use and do an excellent
job of helping to organize what is critical in the
development of the disease. An example is the one
used by peanut growers in the southeastern U.S. for
Tomato Spotted Wilt Virus (TSWV), a virus vectored
by thrips that affects a wide range of crops. Severity
points are assigned based upon plant cultivar (more
susceptible, higher the number), planting date,
population density, insecticide use, row pattern (1 or
2 row), and tillage (conventional or strip). The sum
of the risk values indicates a low, moderate, or high
chance of loss to TSWV. Multiple point models can
be used in more complex systems but also can be
calculated before planting; thus action can be taken to
change the field to a less dangerous situation. For
example, if some fields must be planted at a time for
optimum disease development, then a more resistant
cultivar could be used in those fields.

The most complex type of model is the
simulation model. These models often consider
environmental conditions in real time analysis, thus
determining when plants are most susceptible to an
epidemic. As mentioned above, these models usually
require environmental monitoring equipment that
record data daily every 15 minutes. The data are
input into an algorithm which determines the risk and
length of the conditions for disease development. An
inch of rain that occurred over five hours will have
different effects than an inch of rain that occurred
over 20 minutes and quickly dried up. These models
usually monitor temperature, moisture and dew point,
and sometimes solar radiation, wind speed, and
evaporation potential. The output is similar to
simpler models, usually a range of low, moderate to
severe. This information will lead to better timing of
treatments, preventing crop damage and saving of
sprays. Although simulation models can handle the
complexities of a rapidly changing environment, they


are usually not fine tuned enough to account for
varieties, planting dates, etc. as the multipoint
models.

Ideally, a single or multiple point model could be
applied before the season begins in order to develop
the best strategy for that particular growing season.
The simulation model can be used to add real time
inputs during the growing season. Such hybrid
models are becoming more common, as we continue
to gain a better understanding of what drives an
epidemic.

After the methyl bromide era, a truly integrated
approach to management of soilbome pathogens will
be needed. For example, combinations of effective
nematicides, herbicides, and fungicides will be
necessary based on the pest population history of a
field or expected soilbome pest problems of the
region. Management decisions usually need to be
based on samples taken prior to planting (available
for nematodes). Records of diseases in previous
crops, chemical treatments, and weather will no doubt
have to be used in disease management decisions.
Weather data might be consulted to predict if and
when disease outbreaks will occur, providing good
experimental data exist to predict likely outbreaks.

Prevention and Management
Methods

Site Selection and Preparation

Soilbome diseases remain a major limiting factor
for the production of vegetables in Florida. It is
important to start with clean soil and proper sites for
crops. Plowing and disking will reduce pathogen
carryover in old crop refuse. The longer the fallow
period, the more pathogen populations are reduced. It
is also essential to follow the latest recommendations
for soil fumigation, cultural practices, and biological
control options to eliminate or reduce initial
inoculum of soilbome pathogens. It is important that
soil compaction is avoided, since this interferes with
root growth, encourages soil moisture retention and
promotes root diseases. Preparation of raised beds
generally allows for better drainage. Prior to planting,
soil should be tested for nutrient levels and nematode
populations (and other pathogens if tests are
available). Histories of soilbome disease outbreaks






Integrated Disease Management for Vegetable Crops in Florida 5


are important in prediction of possible future
problems. Planting times can be altered to avoid or
reduce development of certain diseases.

Host Resistance

It is very important to choose cultivars with
multiple pathogen and nematode resistance whenever
possible. In Florida, practical control of many
diseases of vegetables (Fusarium wilt, Verticillium
wilt, and gray leaf spot for tomato) is achieved
primarily by this method. Recently, varieties resistant
to Tomato Yellow Leaf Curl Virus (TYLCV) and
Tomato Spotted Wilt Virus (TSWV) have been
identified. Firm-fruited, crack-resistant tomato fruit
can escape infection of some pathogens.

Irrigation Management

High soil moisture enhances the development of
soilbome pathogens including Phytophthora, Pythium
and the bacterial wilt pathogen. Excess water
damages roots by depriving them of oxygen and
creates conditions that favor infection by certain
soilbome pathogens.

Irrigation management, based on plant needs,
will help to create an environment unfavorable for
pathogen survival and disease development. Use of
tensiometers or other devices for irrigation
scheduling and avoidance of low areas can help in
disease management. For irrigation management
recommendations of University of Florida/IFAS, see
"Irrigation Management" recommendations
(http://edis.ifas.ufl.edu/TOPICVegetableIrrigation).

Soil and Fertilizer Management

Plant nutrition and soil pH can also impact some
diseases. Fertilizers with a higher proportion of
nitrate nitrogen (NO ) than ammoniacal nitrogen
(NH4) will help to reduce the incidence of Fusarium
wilt on tomato. Increasing soil pH by liming is a good
management strategy to reduce Fusarium wilt
incidence as well as Botryis gray mold severity.
Optimum calcium nutrition and higher soil pH may
reduce the incidence of bacterial wilt in the field.
Adequate calcium is necessary to minimize blossom
end rot and to provide for overall healthy growth.
Avoiding excessive nitrogen leads to less dense


canopies, thus improving air movement in the
canopy. For University of Florida/IFAS
recommendations, see EDIS publication HS-711 "Soil
and Fertilizer Management for Vegetable Production
in Florida" (http://edis.ifas.ufl.edu/CV101).

Cultural Practices

Cultural practices serve an important role in
prevention and management of plant diseases. The
benefits of cultural control begin with the
establishment of a growing environment that favors
the crop over the pathogen. Reducing plant stress
through environmental modification promotes good
plant health and aids in reducing damage from some
plant diseases

Sanitation practices aimed at excluding,
reducing, or eliminating pathogen populations are
critical for management of infectious plant diseases.
It is important to use only pathogen-free transplants,
especially for late blight, bacterial spot, viral diseases,
and early blight.

In order to reduce dispersal of soilbome
pathogens between fields, stakes and farm equipment
should be decontaminated before moving from one
field to the next. Reduction of pathogen survival
from one season to another may be achieved by
destruction of volunteer plants and crop rotation.
Removal of cull piles and prompt destruction of
crops should be applied as a general practice.

Avoid movement of soil from one site to another
to reduce the risk of moving pathogens. For example,
sclerotia of Sclerotinia sclerotiorum and Sclerotium
rolfsii, are transported primarily in contaminated soil.
Minimizing wounds during harvest and packing will
reduce post-harvest disease problems. Depending on
crops and other factors, sanitation of soil can be
achieved to some degree by solarization.

Crop rotation is a very important practice,
especially for soilbome disease control. For many
soilbome diseases, at least a 3-year-rotation using a
non-host crop will greatly reduce pathogen
populations. This practice is beneficial for
Phytophthora blight of pepper and Fusarium wilt of
watermelon, but longer rotation periods (up to 5-7
years) may be needed. Land previously cropped to






Integrated Disease Management for Vegetable Crops in Florida 6


alternate and reservoir hosts should be avoided
whenever possible. Vegetable fields should be
located as far as away as possible from inoculum and
insect vector sources.

Weed control is important for the management
of viral diseases. Weeds may be alternate hosts for
several important vegetable viruses and their vectors.
Elimination of weeds might reduce primary
inoculum. Cover crops help to reduce weed
populations that may harbor pathogens between
seasons. For this purpose use cover crops that grow
fast and provide maximum biomass. Non-host cover
crops will help to reduce weed populations and
primary inoculum for soilbome pathogens.

Excessive handling of plants such as in thinning,
pruning and tying may be involved in spread of
pathogens, particularly bacteria. It is advisable to
handle plants in the field when plants are driest.
Because some pathogens can only enter the host
through wounds, situations which promote plant
injury should be avoided. During pruning process and
harvest, workers should periodically clean their hands
and tools with a disinfectant, such as isopropyl
alcohol.

If applicable, plants can be staked and tied for
improved air movement in the foliar canopy. A more
open canopy results in less wetness, discouraging
growth of most pathogens.

Soil aeration and drying can be enhanced
through incorporation of composted organic
amendments in the soil. Build up of inoculum can be
reduced by removing all plant materials (infected and
apparently healthy) after harvest. Between-row cover
crops reduce plant injury from blowing sand.

Polyethylene mulch can be used as a physical
barrier between soil and above-ground parts of plants.
This is an important practice for fruit rot control in
the field. Highly UV-reflective metalizedd) mulches
repel some insects. It is beneficial to use metalized
mulch during certain times of the year when insect
vectors of some viral diseases are prevalent. Tomato
spotted wilt virus (TSWV) incidence and associated
vector thrips populations have been demonstrated to
be effectively reduced by using metalized mulches on
tomatoes. Metalized (UV-refelctive) mulches can not


be used during winter in southern Florida and early
spring in northern Florida, because soil temperatures
do not reach desirable levels.

Biological Control

Biocontrol agents for use in vegetable disease
management are increasing in use especially among
organic growers. These products are considered safer
for the environment and the applicator, than
conventional chemicals and are mainly used against
soilbome diseases. Examples of commercially
available biocontrol agents include the fungi
Trichoderma harzianum and Gliocladium virens, an
actinomycete Streptomyces griseoviridis, and a
bacterium Bacillus subtilis. Bacteriophages (phages)
have been found as an effective biocontrol agent for
the management of bacterial spot on tomato. Phages
are viruses that infect bacteria. It is best to run small
trials on ones own farm to fully evaluate the
applicability of biocontrol to particular farming
operations.

Chemical Control

Fungicides and bactericides are an important
component of many disease management programs.
It is important to remember that chemical use should
be integrated with all other appropriate tactics
mentioned in this chapter.

Information regarding physical mode of action
of a fungicide will help producers improve timing of
fungicide applications. Physical modes of action of
fungicides can be classified into four categories:
protective, after infection, pre-symptom, and
anti-sporulant (post-symptom). Protectant fungicides
include the bulk of the foliar spray materials available
to producers. In order to be effective, protectant
fungicides, such as copper compounds, mancozeb
etc., need to be on the leaf (or plant) surface prior to
arrival of the pathogen. Systemic (therapeutic)
fungicides, based on their level of systemicity [true
systemic (i.e. Aliette), translaminar (i.e. Quadris),
meso-systemic (i.e. Flint)], are active inside of the
leaf (can penetrate at different rates through the
cuticle). Systemic fungicides may stop an infection
after it starts and prevent further disease development.
If necessary fungicides must be used based on






Integrated Disease Management for Vegetable Crops in Florida 7


recommended fungicide resistance management
strategies.

A new strategy to chemically manage plant
diseases without direct interference with the pathogen
is the triggering of plant defense reaction.
Acibenzolar-S-methyl (Actigard), a chemical in this
category, was registered for the control of bacterial
spot and speck on tomatoes.

Chemicals must be used at recommended rates
and application frequencies. Besides selection of the
most efficacious material, equipment must be
properly calibrated and attention paid to the
appropriate application technique. As always, the key
to effective disease management is correct diagnosis
of the problem.

Follow the latest fungicide recommendations
given by the University of Florida, Cooperative
Extension Service publications (See current version
of Extension Plant Pathology Report No.6 by Tom
Kucharek). Always read the pesticide labels and
follow the instructions carefully. Remember, the
label is the law. Fumigants can be used to manage
soilbome pathogens. Before applying, it is important
to review the disease history of the specific site when
choosing fumigant materials.

Effective management of whiteflies, thrips, and
aphids should be practiced to reduce the incidence
and secondary infections of viral diseases vectored by
these insects. Apply University of Florida/IFAS
recommendations for insect management
(
http://edis.ifas.ufl.edu/
TOPICGUIDEInsect Management Guide).




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