Front Cover
 Know your common, disease-causing...
 Do-it yourself diagnostic key for...
 Disease and nematode control
 Four keys to pesticide safety
 Back Cover

Group Title: Circular - Florida Cooperative Extension Service - 399-A
Title: Diagnosis and control of plant diseases and nematodes in a home vegetable garden
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00067898/00001
 Material Information
Title: Diagnosis and control of plant diseases and nematodes in a home vegetable garden
Series Title: Circular Florida Cooperative Extension Service
Physical Description: 29 p. : ill. (some col.) ; 23 cm.
Language: English
Creator: Kucharek, Tom ( Thomas Albert ), 1939-
Dunn, Robert Arthur
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville
Publication Date: 1984?
Subject: Vegetables -- Diseases and pests -- Florida   ( lcsh )
Nematode diseases of plants -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: Tom Kucharek and Bob Dunn.
General Note: Cover title.
Funding: Circular (Florida Cooperative Extension Service) ;
 Record Information
Bibliographic ID: UF00067898
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, Board of Trustees of the University of Florida
Resource Identifier: oclc - 15174846

Table of Contents
    Front Cover
        Front Cover 1
        Front Cover 2
        Page 1
    Know your common, disease-causing pests - Fungi, bacteria, viruses, nematodes, abiotic causes
        Page 1
        Page 2
        Page 3
    Do-it yourself diagnostic key for some common vegetable diseases present in Florida home gardens
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
    Disease and nematode control
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
    Four keys to pesticide safety
        Page 29
    Back Cover
        Page 30
Full Text


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source

site maintained by the Florida
Cooperative Extension Service.

Copyright 2005, Board of Trustees, University
of Florida


Diagn iP.fl Florida
Control r'Pain-
Diseases and
Nematodes in a
Home Vegetable

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

JAN 7 107

The use of trade names in this publication is solely for the purpose of
providing specific information. It is not a guarantee, warranty, or endorse-
ment of the products named and does not signify that they are approved
to the exclusion of others.

Diagnosis and Control of
Plant Diseases and Nematodes
in a Home Vegetable Garden

Tom Kucharek and Bob Dunn*

Vegetable gardening is a popular pastime in
Florida. Many Floridians, now growing their own
vegetables, find it gratifying to display their skills.
Unfortunately, many gardeners have experienced
failures because of diseases and nematodes.
Disease-causing organisms such as fungi,
bacteria, nematodes and viruses are some of the
greatest enemies of a gardener. These pests can ruin
a garden and discourage the gardener. What makes
this situation confusing is that in many cases you
can not see these organisms with the naked eye; you
see only the damage that they cause.
Can plant diseases and nematodes be controlled in
a vegetable garden? The answer is yes. Further-
more, they can be controlled easily without a major
drain on the pocketbook.

Know Your Common, Disease-Causing
Pests Fungi, Bacteria, Viruses,
Nematodes, Abiotic Causes
Fungus (Fungi). Often called molds, fungi are
plants without roots, stems, leaves or chlorophyll.
Most fungi produce spores (microscopic seeds) of
which some serve as survival structures, some serve
in sexual reproduction and some serve as means by
which the fungus is dispersed via wind, water, in-
sects, or implements.
Spores of the fungus that cause a leaf spot on corn
are approximately 1/250 of an inch long. When
favorable moisture and temperature conditions are

*Professor- Extension Plant Pathologist, Department of Plant
Pathology; and Associate Professor-Extension Entomolo-
gist, Department of Entomology and Nematology. Institute of
Food and Agricultural Sciences, University of Florida, Gaines-
ville, Florida 32611.

Diagnosis and Control of
Plant Diseases and Nematodes
in a Home Vegetable Garden

Tom Kucharek and Bob Dunn*

Vegetable gardening is a popular pastime in
Florida. Many Floridians, now growing their own
vegetables, find it gratifying to display their skills.
Unfortunately, many gardeners have experienced
failures because of diseases and nematodes.
Disease-causing organisms such as fungi,
bacteria, nematodes and viruses are some of the
greatest enemies of a gardener. These pests can ruin
a garden and discourage the gardener. What makes
this situation confusing is that in many cases you
can not see these organisms with the naked eye; you
see only the damage that they cause.
Can plant diseases and nematodes be controlled in
a vegetable garden? The answer is yes. Further-
more, they can be controlled easily without a major
drain on the pocketbook.

Know Your Common, Disease-Causing
Pests Fungi, Bacteria, Viruses,
Nematodes, Abiotic Causes
Fungus (Fungi). Often called molds, fungi are
plants without roots, stems, leaves or chlorophyll.
Most fungi produce spores (microscopic seeds) of
which some serve as survival structures, some serve
in sexual reproduction and some serve as means by
which the fungus is dispersed via wind, water, in-
sects, or implements.
Spores of the fungus that cause a leaf spot on corn
are approximately 1/250 of an inch long. When
favorable moisture and temperature conditions are

*Professor- Extension Plant Pathologist, Department of Plant
Pathology; and Associate Professor-Extension Entomolo-
gist, Department of Entomology and Nematology. Institute of
Food and Agricultural Sciences, University of Florida, Gaines-
ville, Florida 32611.

present on host tissue or other substrates, spores
germinate and then produce more spores or a germ
tube. Continued growth of the germ tube results in
the production of structures that facilitate host
tissue penetration or production of a prolific net-
work myceliumm) of microscopic threads hyphaee)
capable of growth in or on soil, seed, leaves, stems
and roots. A mushroom is a fungus that is visible
because hyphae have grown together. Bread mold is
another example of a fungus. Certain fungi, like
those causing rusts, powdery mildews and downy
mildews, require living plant tissue to complete
their life cycles.
Fungi enter plants and cause stunting, spots,
blights, galls, rots or "mildew" on all plant parts.
Each fungus species that infects a plant produces
characteristic symptoms. Similar symptoms can
result from infection by different fungus species.
The time between entry of the fungus (infection) and
appearance of the symptoms is called the incubation
period. Incubation periods of 3 to 7 days are typical
for downy mildew diseases of cucurbits and crucifer
crops while 5 to 14 days of incubation are typical for
most other leaf-infecting fungi. Temperature,
moisture, and other factors influence disease
development. The importance of this information is
related to control. From one infection, thousands of
spores can form in the diseased tissue. Because of
the ability of fungi to multiply at fast rates, control
methods are most effective when applied early.
Bacterium (Bacteria). Bacteria are microscopic,
one-celled, living organisms that multiply by cell
division. A typical cell of a bacterium is about
1/12,000 of an inch long. Bacteria cause stunting,
leaf spots, wilts, fruit rots or galls. Bacteria can live
and multiply in seeds, seed pieces, transplants, soil
and weeds. Once introduced into a garden, bacteria
are spread chiefly by rain and irrigation (especially
wind driven rains). Plants have natural openings
through which bacteria can enter. Insects and
wounds to a plant provide additional entry points
for bacteria. Incubation periods of 3 to 7 days are
typical for bacterial leaf spots such as bacterial spot

on tomatoes and peppers. Like fungi, bacteria pro-
duce extremely large numbers of propagative struc-
tures in one spot; therefore, bacteria are controlled
best by applying control measures early.

Virus (Viruses). These are particles containing a
nucleic acid core (genetic material) surrounded by a
protein coat. A tobacco mosaic virus particle is ap-
proximately 1/80,000 of an inch long. Symptoms of
virus diseases include leaf mosaics and mottles,
fruit mosaics, leaf distortions and stunting. Often, it
is difficult to distinguish disorders caused by
viruses, herbicides and nutrient deficiencies.
Viruses can be spread by contaminated seed,
especially on beans and southern peas. Further
spread of many viruses within a garden is caused by
aphids. Gardens beside weedy fields or ditches are
more apt to have aphid-transmitted viruses on
cucurbits. Tobacco mosaic virus, which is most apt
to be a problem on tomatoes and peppers, can be car-
ried in tobacco products. Incubation periods from a
few days to several weeks are typical for virus
diseases. Host vigor and age, environmental factors
and many other variables influence incubation
periods for virus diseases.
Nematode (Nematodes). Nematodes are round,
worm-shaped animals, many of which live in the soil.
Hundreds of different kinds, most harmless or even
beneficial, live in Florida soils. A few which feed on
or in plants are commonly called plant parasitic
nematodes and may severely reduce the health,
vigor, productivity, and value of vegetables. Stunt-
ing, wilting and slow growth are common symptoms
of plants infected by nematodes.
Plant parasitic nematodes must feed on plant
tissues to be able to complete their life cycles.
Adults are generally 1/100 to 1/8 inch long. Each
plant nematode feeds by means of an oral stylet or
spear. This is a sharp hollow point, much like a
hypodermic needle, with which nematodes puncture
plant cells on which they feed.
Root-knot nematodes are the most damaging and
common kinds in home gardens. They enter roots

near the young tips, where their feeding stimulates
growth of the root tissues, resulting in production of
swollen galls. Nearly all common vegetables can be
injured by one or more of the three species of root-
knot nematodes which occur most commonly in
Sting and stubby root nematodes can also cause
serious injury to vegetable crops. They feed on the
outer surfaces and tips of roots, causing the root
system to be greatly stunted, often with fewer fine
branch roots and very short branch or lateral roots.
Abiotic Causes. Another group of problems aris-
ing in home gardens is caused by nonliving agents.
Nutrient deficiencies and herbicide damage are com-
mon. Blossom end rot of tomatoes and peppers is
caused by a calcium deficiency in blossom ends of
fruits. Such may result even when adequate calcium
is present in the soil, if soil moisture fluctuates from
wet to dry during crop growth. Herbicides used on
lawns may drift into garden areas, causing plant
deformation. Proper use of fertilizers and weed
killers will remedy these situations. Chemical burns
from insecticides, fungicides, and excessive fertiliza-
tion are also classed as abiotic diseases. A good rule
of thumb for beginners is to apply insecticides,
fungicides and foliar nutrient sprays separately;
mixing materials (tank mixes) is faster, but occa-
sionally disastrous. Using correct amounts of
fungicides, insecticides and fertilizer will prevent
problems. Labeled rates of pesticides are effective if
application timing is correct. USE CHEMICALS

Do-It-Yourself Diagnostic Key
for Some Common Vegetable Diseases
Present in Florida Home Gardens
The purpose of this key is to help home gardeners
diagnose common plant diseases and nematodes oc-
curring in their vegetable gardens. If the disease is
properly diagnosed, the correct control measures
can be chosen. Often people spray a chemical in-

discriminately to control some unknown disorder
that can not be controlled by spraying. To use this
key, first decide if leaves, roots and stems, or fruit
are diseased by using numbers I, II or III. Then,
select the disease type within the respective number
that best fits your situation. It is possible that more
than one disease or disease type is occurring at the
same time on a specimen.
This generalized diagnostic key is not designed to
identify all problems. If you encounter a problem
that can not be resolved by use of this key, contact
your county extension staff for additional
assistance. Diagnosis is done best on plants that are
less than 50 percent blemished. Dead plants should
not be used. Placing diseased plant tissue within a
plastic bag with wet paper toweling for 1 to 2 days
will encourage formation of fungus structures used
for identification in this key. See Table 1 for appro-
priate control measures) after you have diagnosed
the problem.


I. Leaves have definite spots,
white growth or other ab-
normal symptoms.

A. Upper or lower sides of Powdery mildew
leaves have white powdery
growth; common on English
peas, squash, cucumbers,
pumpkins, beans, okra,
melons, and Southern peas.

B. Leaves have reddish-brown Rust
raised pustules not larger
than 1/8 inch that deposit a
reddish-brown or orange
color on a white handker-
chief when rubbed across
pustules; common on beans,
Southern peas, and sweet

C. Crop is squash, cucumber, Downy mildew
melon or some other cucur-
bit and leaves have yellow
to brown, often angular,
spots (1/4" or less) on upper

leaf surface. Lower leaf sur-
face has a downy mold
growth within spots.

D. Leaves and sometimes
stems with distinct dark
colored or tan spots 1/16
inch to 1 inch across. Some
sweet corn leaf spots are up
to 5 inches long. Common
on most vegetable crops.
See Figure 1.

E. Leaves with mosaic or
mottled appearance (non-
uniform or diffuse shades of
green and yellows). The
separation of these colors is
not always sharp. Dark
green bands adjacent to leaf
veins. In beans, some leaf
distortion may occur in the
form of puckering or altered
leaf shape. Stunting follows
if plant infected when not
mature. Fruit may have
similar symptoms and may
be distorted. (See Cover

F. Leaves and sometimes
stems twisted, deformed, ex-
cessively curled and leath-
ery without change in color.

Leaf spots (including
downy mildews of
crucifers and onions)


Herbicide damage
(2, 4-D type)

Figure 1.

Leaves may be abnormally
long and narrow. Leaf veins
are often enlarged and sinu-
ate. Tomatoes are very sus-
ceptible but most crops are

G. Leaves lack symptoms A
through E but may have
yellow to brown color that
predominates on margin of
leaves and between major
veins. See Figure 2.

Soil-borne problem
(See No. II.)

II. Plants (including seedlings) stunted, or wilted, or leaves
turning yellow to brown, usually lower leaves first.
Yellowing and browning of leaves begins along margins
of leaves and between major veins.

A. Seedling stem rotted near
soil line, or roots with ob-
vious spots, or rotting.

B. Roots have swollen knots or
galls and may lack feeder
roots. See Figure 3.

C. Seedling is stunted and
yellow; roots are stunted or
mostly absent. Some rotting
may follow these initial
symptoms. See Figure 4.

D. White mold growth seen on
outside of lower stem and

Seedling blight

Root-knot nematode

Sting, stubby root,
or other nematodes

White mold (southern

Figure 2.

Figure 3.

nearby debris on soil.
Round, mustard-seed-sized
bodies present on lower
stem with mold growth.
These are first white and
turn brown with age. Outer
and inner stem discolored.

E. Slicing stem lengthwise of
tomato, sweet potatoes,
watermelon, cabbage,

Figure 4.

Fusarium wilt
(Possibly Verticillium
wilt on tomato, okra

"I~ r-


Southern pea or bean ex-
poses two brown to reddish-
brown streaks originating
from roots. Lower leaves
often yellow. Early yellow-
ing of lower leaves may be
on one side of plant only.
Plants may be wilted. See
Figure 5.

F. Slicing stem of tomato
lengthwise exposes a brown
inner stem or brown streaks
similar to Fusarium wilt.
Plants wilted and limp, but
may remain green. During
cooler periods less wilting
occurs and lower leaf yel-
lowing may occur. Recovery
from wilt may not occur
during cool periods of the
day, or by early morning.
White streaks of ooze are
discharged within 3 minutes
when a cut end of stem is
held in a glass of water.

G. Slicing stem lengthwise re-
veals a grayish-white mold
growth often with hard
black bodies 1/4 to 1/2 inch
in length inside of stem.

or eggplant in Home-
stead area of Florida
or on heavily limed

Bacterial wilt of

(stem rot)

Figure 5.

Common on many vege-
tables in south and central
Florida. Rare in north Flor-

H. Lower stem and/or roots
discolored without any
characteristic structures or

Root or stem rot
other than already

III. Fruit, tuber, edible root or edible part of plant
blemished or infected.

A. Fruit or edible part is soft,
slimy and watery. Offensive
odor present. Wound
damage or insect tunnels
present. No mold growth
present. Common on toma-
toes, peppers, potatoes,
broccoli, turnips, cabbage,
and leafy vegetables ex-
posed to heavy rains.

B. Fruit or edible part of plant
has hard black bodies 1/4 to
1/2 inch in length. Common
on cabbage, lettuce, endive,
beans and carrots in central
to south Florida. White to
gray mold growth may also
be present.

C. Problem fruit is strawberry
and has a gray mold or tan
spots on fruit.

D. Problem fruit is bean and
has sunken lesions, purple
in color, or bordered by
purple coloring with the
center having pink mold
growth. Spots on leaves
sometimes present. Com-
mon on lima beans.

E. Underside of fruit in contact
with soil has a rot that
appears to be a reddish-
brown crater. At first dry
but later slimy. Common on
cucumber, beans and

F. White mold growing on
fruit; soft slimy rot also
present. Common on cu-
cumber and squash.

Soft rot

(stem rot)

Gray mold or hard
brown rot


Belly rot

Cottony leak

G. Dark whisker-like fungus Wet rot
growth on fruit or spent
flower petals. Wet rot
present. Common on squash
and southern peas.
H. Fruit has alternating areas Virus
of greens and yellows.
Warts or knobs present.
I. Side of pepper or tomato Sunscald
fruit facing sun with white
or yellow, sunken wrinkled
area. Often entire side of
fruit affected.

J. Blossom-end of tomato or Blossom-end rot
pepper with sunken, dark
areas on pepper. Affected
areas may include side of

Disease and Nematode Control
Disease and nematode control in a home garden
should be conducted as a total program using a se-
quence of control measures. No one control practice
by itself is adequate. Table 1 summarizes what
should be done before and after planting. The follow-
ing text information details those control measures.

Before Planting
The control of plant diseases and nematodes is
done best by preventing their occurrence. Control is
often difficult or impossible after certain diseases
become severe. Thus, what you do early is most im-
I. Site Selection. A sunny location is good for
vigorous plant growth and for reducing disease
development. Diseases are reduced because the
retention of moisture on leaves is minimized and
because of vigorous plant growth. Moisture on
leaves is necessary for fungal spore germination and
bacterial cell ingress.
II. Drainage Preparation. Excess soil moisture is
conducive for growth of certain soil fungi and
nematodes causing root rots. Excess soil moisture
can deplete oxygen for the root system thereby
slowing root development and predisposing roots to

Table 1. Major control measures for plant diseases of vegetables in vegetable gardens.1
+ + + Excellent method of control.
+ + Good method of control.
+ Some control may be obtained.

/t I .J^ lMi.!,J, J.


Root knot

+++ ++ I +


Other nematodes + + +++ + +++ +
Anthracnose + +++ + + + + +++ +
Rust + + + ++ + +
Downy mildew +++ ++ + +++ +
Powdery mildew +++ ++ + +++ +
Leaf spots + + ++ + + ++ + ++ + + ++ + +
Virus + +++ +++ ++2 +
Soft rot + + + ++ + + +
Belly rot + + + + + +
Wet rot + + +
Cottony leak + + ++ + +++ +
Gray mold + + + + ++ +
Sunscald Maintain healthy foliage
Blossom-end rot Lime soils and avoid fluctuation in soil moisture
Herbicide damage Careful and correct use of herbicides

1 See text for details.
2 Good to excellent control when available.
3 Primarily for squash after fruit is set.

+ + +

infection by soil fungi. If you do not use elevated
beds (rows) in your garden, slope the garden
slightly. If a level or sloped garden is used it should
be slightly elevated from the surrounding area. This
will aid water runoff during heavy rains and reduce
rain water from washing into the garden from out-
side areas, bringing with it microorganisms that
cause plant diseases.
III. Soil Tillage. Undecomposed plant debris or
green plant matter (including weeds) can be a source
of fungi, bacteria, nematodes, and viruses that
cause plant diseases. Such organic materials also
impede movement of fumigant vapors, thereby leav-
ing sources of inocula (spores, cells, eggs, etc.), for
future of plant disease even though the soil was
fumigated. The soil should be turned over with a
shovel or a plow 6 inches or more, preferably 30
days prior to planting, transplanting or fumigating.
If a roto-tiller is used, more than 30 days or multiple
tilling may be necessary to achieve adequate de-
composition. Decomposition of organic materials
is enhanced if the garden area is "plowed down"
immediately after harvest of each crop.
IV. Purchase Disease-Free-Seed and Seed Pieces.
Many fungal, bacterial and viral diseases can be
transmitted by seed. This is especially true for
beans (snap and limas), and peas (English and
Southern). It is best to purchase seed produced in
the dry climate of the western United States.
Vegetable seed produced in that area (California,
Oklahoma, Wyoming, Colorado), are more apt to be
free of disease-causing organisms.
Potato seed pieces should be from certified seed
potatoes only. Do not use table stock potatoes for
seed pieces as they may be carrying diseases and
furthermore, may be treated with sprout inhibitors.
Seed roots used for producing sweet potato
transplants (draws, slips) should be free of any signs
of disease or blemish.
V. Fungicide Seed Treatment. Seed treatment
with a fungicide reduces seed rot and preemergent
seedling decay caused by fungi. Seed treatment
fungicides do not eliminate fungi from seed; the

main purpose of such a treatment is to protect the
seed and preemerged seedling from decay caused by
fungi in the soil. No control of bacteria or viruses in
seed should be expected with fungicide seed treat-
ment. Bacterial rot of potato seed pieces may be
reduced with a fungicide treatment.
Seed treatment is suggested, even if you fumigate
soil, and, should be considered strongly if the
garden is not fumigated. Bulk vegetable seed sold at
garden shops is often treated with a fungicide,
whereas seed sold in small packets often is not
treated. If seeds appear coated with brightly colored
dye (red, blue, purple, green), that is a sign that the
seeds have already been treated.
For untreated seeds, purchase a seed treatment or
seed protectant fungicide with thiram or captain as
the active ingredient. These two fungicides are
cleared for use on many vegetable crops. Thiram is
available in small packages for homeowners as Seed
Protectant from Science Products Company in
Chicago. Use rates listed on the label. For small
quantities of seed, such as those in packets, apply
the equivalent of a match head or two per packet.
Close the packet and shake well to distribute the
material over the seed.
For potatoes, Manzate 200, Dithane M-45 or a
labeled zineb fungicide used as a dust at the rate of
one lb/100 lbs of cut seed pieces will reduce seed
piece rots. After cutting seed into pieces (4 oz/piece
is best), allow pieces to dry and suberize on a table;
treat with the fungicide immediately before plant-
VI. Use Healthy Transplants. It is as important
for transplants to be disease free as it is for seed to
be disease free. Transplants which are purchased
should be healthy, vigorous and well cared for. If
roots have galls or symptoms of disease, do not buy
them. Sweet potato diseases are controlled primar-
ily by use of disease-free transplants.
If possible, grow your own transplants. Before
planting the seed, pasteurize the soil and all con-

tainers in an oven by heating at 180 *F. for one hour.
This procedure will kill most parasitic fungi,
bacteria and nematodes. Pasteurized or sterile soil
mixes (such as Metro Mix) are commercially
available with starter fertilizers included. Plant con-
tainers, tools, benches and other related materials
can be sanitized by soaking in a bleach solution for
15 minutes. Maintain the seedlings in a location
where they will be exposed to sunlight and on raised
benches where they will not be contaminated from
soil or debris.
Healthy transplants can be produced within the
garden site, especially if soil is fumigated.
Do not damage seedlings in the process of pulling
and setting transplants. Injury to young plants
(many broken roots, stem cuts, seed leaf abcission,
etc.) retards plant development throughout its life
span and makes the plant prone to infections from
pathogens (agents causing plant diseases).
VII. Soil Treatment for Nematodes and Soil-
Borne Diseases. At present, soil treatment before
planting the crop is the most reliable means of con-
trolling a wide variety of nematodes and soil-borne
diseases of vegetable gardens. Only one chemical
(SMDC), sold under several trade names (Vapam,
Fume V) is available for effective control of
nematodes, most soil-borne diseases, and many
weeds in soil where the home garden will be planted.
A non-chemical method of treating the soil, "soil
solarization," has been used successfully in some
cases but has failed in others.
Advance planning is necessary for either chemical
or solar soil treatment. Site preparation must be
done at least 2 weeks before starting either method.
Fumigation requires at least 2 weeks from applica-
tion to planting. Soil solarization takes 4 to 6 weeks
to complete.
Soil preparation is critical for success of either soil
fumigation or solarization. Coarse root pieces which
might protect nematodes or fungi from the treat-
ment should be removed from the soil before start-
ing. The soil should then be tilled to break up
smaller pieces of plant material so they will decom-

pose before the treatment is applied. When the
chemical fumigant or solarization treatment is ap-
plied, the soil should be in good seed-bed condition,
with soil moisture and tilth appropriate for planting
fine seeds.
Soil fumigation is a treatment of the soil with a
liquid chemical which turns to a gas and spreads
evenly through the soil for maximum pest suppres-
sion. The only effective chemical currently available
to home gardeners for control of soil-borne pests is
SMDC (metam-sodium), marketed as Vapam and
Fume V. Best control is achieved by applying the
fumigant when soil temperature 4 inches deep is be-
tween 60*F and 90*F (15 to 32*C). Three common
and effective methods of application are outlined
below. Consult product labels for additional infor-
Application of SMDC by sprinkling can. Place
one pint (473 cc) of SMDC in a sprinkling can, fill the
can with water and stir (not with your hand).
Sprinkle evenly over 50 sq ft (4.7 sq m) of row or bed
area. Evenly apply additional water by sprinklers or
hose until at least 1/2 inch (1.3 cm) or about 16
gal./50 sq ft of water has been applied over the
treated area, to wash the SMDC into the soil. Rinse
can thoroughly before use on living plants.

Application of SMDC with hose-end sprayer.
Place one pint (473 cc) of SMDC in the cannister of
the sprayer and fill with water. Spray evenly over 50
sq ft (4.7 sq m; approximately 100 cc/sq m) of bed or
row. Continue to spray soil surface until enough
water (16 gallons) has been added to wet the soil 6
inches (15 cm) deep. Rinse sprayer thoroughly
before use on living plants.
Application of SMDC in furrows. SMDC may be
applied by dribbling it into furrows from a fruit jar
with two nail holes punched in opposite sides of the
cap. Place one pint (473 cc) in the jar, fill with water
and recap. Walk steadily along the row dribbling the
liquid in the bottom of the furrow. Dribbling SMDC
into a single furrow treats a 6-inch (15 cm) band
(width) of soil, because fumes spread about 3 inches
to either side of the furrow. For row treatment it

should be applied to two furrows, 6 inches apart,
straddling the intended row center. For broadcast or
overall treatment, space furrows 6 inches apart
across the entire area. Use SMDC at the rate of 1
pt/50 sq ft of bed or 100 ft of furrow (100 cc/sq m or
155 cc/10 m of furrow). Since two furrows should be
used for row treatment, 1 pt will treat 50 ft of row,
12 inches (30 cm) wide. Cover the furrows with soil
immediately after treating each 100 ft (30 m) of fur-
Sealing soil after applying SMDC. SMDC is not
effective unless it is "sealed" into the soil for 2 to 3
days. The simplest method is to lightly sprinkle the
treated area with water to keep the surface moist for
at least 2 days after application. A far more effec-
tive "seal" is to cover the treated area with a sheet
of plastic film or heavy paper immediately after
treatment. Bury the edges of the cover with soil to
reduce loss of fumes from the sides of the treated
area and anchor the cover against wind. Remove the
cover from the soil after 2 days to permit the fumes
to escape from the soil before planting. Do not allow
soil that was used to bury the edges of the cover to
fall into the treated area. Adjacent, untreated soil is
a likely source of recontamination.
Waiting period. SMDC is toxic to seeds and plant
roots. Do not plant into treated soil until sufficient
time has passed for the fumes to escape. Wait at
least 2 weeks after applying SMDC. If soil is ex-
cessively wet or cold (below 60"F) (15*C) during the
2 weeks after treatment, the waiting period may
have to be longer. Do Not Plant if the odor of the
fumigant is easily detected in the treated soil.

Soil Solarization is the process of covering soil
with a clear plastic sheet so the sun will directly
heat the soil and the plastic tarp will trap the heat.
During the summer, when sunlight is most direct,
the area under the plastic will become as much as 15
to 20 F hotter than normal soil temperatures.
Treatment for 4 to 6 weeks may reduce soil
nematode and fungus populations a foot deep or
more. The effect is most complete near the surface of
the soil, and progressively less so with depth.

Following is a brief outline of procedures and
precautions to follow when trying soil solarization.
1. Soil should be covered for 4 weeks, preferably
longer, during the hottest and sunniest period
of the year. June, July and August appear to be
most suitable.
2. Soil must be well tilled before covering as de-
scribed earlier to maximize conduction of heat
through the soil and contact between the tarp
and soil surface. All other soil preparations
such as fertilization and placement of drip irri-
gation tubes should be completed before apply-
ing the cover. This will minimize the need to
disturb the treated soil before planting.
3. Soil moisture must be high when the cover is
applied. Heat is more efficiently conducted
through wet soil than dry soil.
4. It may be desirable to raise beds slightly to
reduce the chances of recontamination after
planting, but excessively high and narrow beds
result in poor heat retention during night and
cloudy periods.
5. Covering broad areas, including paths and row
middles, will reduce the overall population of
soil pests and should reduce opportunities for
recontamination of planted areas.
6. Use clear polyethylene, not black mulch. Sun-
light passes through clear plastic to heat the
soil directly. Black plastic intercepts the sun-
light and soil is heated only by conduction
where soil contacts the plastic.
7. Thin plastic mulch (1 to 2 mil) may permit
more sunlight to penetrate to the soil and may
favor more rapid and deeper control of soil-
borne fungi than thicker plastic (6 mil). How-
ever, adequate control can be obtained with
both thicknesses, and the thicker plastic is less
likely to tear.
8. Leaving the tarp in place until you are ready
to plant will maximize the treatment and re-
duce the chance of recontamination.
9. After spending so much effort, time, and
money, avoid recontaminating the treated soil.

Burning old plant debris from pruning or rogueing
on the garden site reduces soil pests. The effec-
tiveness of this method is dependent upon the depth
the heat is conducted and the time exposure. Do not
use this technique without permission from the
county forester.
Soil treatment of any kind lasts only one season.
No pesticide or non-pesticide treatment provides
perfect or everlasting control. The treatments
described reduce soil pest populations at the begin-
ning of the season so plants can get off to a good
start and produce a good crop. By the end of the
growing season you may have as many soil pests as
with non-application of a soil treatment.
VIII. Crop Rotation. Alternating the crops
planted on a given site within the garden or
relocating the garden spot, preferably in an old
grass site, each year reduces disease. This method
should be considered a must if you do not fumigate
or solarize the soil. However, do not expect disease
control by crop rotation to be as effective as that
achieved by soil treatment, especially in small areas.
Crop rotation is somewhat effective because cer-
tain pests that infect one type of plant will not infect
another type. Pathogens are reduced in numbers
when favorable host plants are not present. If you
use crop rotation it would be best to alternate sweet
corn with the other vegetable types.
IX. Use of Raised Beds and Mulches. Raised
beds are helpful in minimizing excess water damage
caused by heavy rains or overzealous irrigation
which predisposes plants to root and stem rot fungi
and bacteria. If a mulch (plastic, pine needles or
grass clippings) is not used on raised beds, the soil
will dry out faster causing plant stress and further
predisposition to root rot fungi. Some drying out at
the soil surface is advantageous as crown rots and
lower stem rots are reduced.
Mulches also reduce fruit rot on crops such as
strawberries, squash, cucumber, or melons as the
fruit will not be in direct contact with the soil.
X. Fertilizer and Lime Usage. Excess fertilizer,
especially when placed in bands rather than broad-

cast, can cause root, stem and leaf damage (salt
burn). On young plants salt burn can be lethal and
on older plants salt burn is debilitative. Excessive
or insufficient fertilizer amounts are debilitative and
stressful to plant growth. Plant roots are more apt
to be infected by fungi in such situations.

Maintaining a soil pH within a range of 6.2-6.5
with lime or preferably dolomitic limestone (con-
tains magnesium) will provide for necessary
nutrient (fertilizer) availability plus reduce root colo-
nization by some soil-inhabiting root rot fungi,
especially Fusarium spp. Also, adequate calcium
(supplied by lime or dolomitic limestones) is
necessary for shoot growth of plants and minimiz-
ing blossom end rot of tomatoes and peppers.
Avoid excess nitrogen fertilizer when starting
plants from seed or transplants. A starter fertilizer
with less nitrogen than phosphorous, such as a 6-8-8
(nitrogen-phosphorus-potassium) will accentuate
root development early in relation to shoot growth.
Side dressings with nitrogen can be applied later to
accentuate shoot development once a good root
system is established. Such an approach will result
in sturdier plants which are less likely to lodge. For
tomatoes, maintaining a 1:1 1/2 or 1:2 ratio of
nitrogen to potassium will produce higher quality
fruit. Yellow shoulder on ripened tomato fruit will
be reduced. For potatoes, maintain adequate
nitrogen side dressings to reduce early senescence
and susceptibility to early blight (a common leaf
spot disease on potatoes).
Use a preplant fertilizer with "minor elements"
(copper, manganese, zinc, iron, boron, etc.) or apply
them separately. The so called "minor" elements are
major contributors to plant vigor and their defi-
ciency symptoms are difficult to diagnose and cor-
rect. Spraying minor elements on foliage after symp-
toms appear may not correct the problem early
Advanced gardeners have a tendency to use more
fertilizer. To minimize plant stress from high fer-
tilizer rates, a higher soil moisture must be main-
tained continuously.

XI. Resistant Varieties. The damage caused by
some pests to many vegetable varieties is nonexist-
ent or not as great as for other varieties of the same
plant species. Resistance does not always mean
that 100 percent of the plants are resistant; a few
may be susceptible or only a small amount of a
given disease appears on each plant.
The gardener should also realize that just because
a variety is resistant to one disease does not mean it
is resistant to all diseases present in Florida. For ex-
ample, Walter and Floramerica tomato varieties are
resistant to Fusarium wilt but not bacterial wilt
which is common in some Florida gardens. Certain
varieties of watermelon, cabbage and sweet
potatoes are somewhat resistant to Fusarium wilt.
Some tomato varieties are listed as resistant to the
southern root knot nematode by the "N" designa-
tion of VFN or VFNM. It is important to realize
that the nematode resistance is not effective when
soil temperatures are greater than 81OF (27C) and
not effective against other kinds of nematodes. Such
resistance can be beneficial in spring gardens where
plants are started in cooler temperatures. When
tomatoes are planted in warm soil, such as in fall
gardens in northern Florida or at many times in
southern Florida, nematode resistance in tomatoes
is unreliable.
If you fumigate your soil you may not have to use
varieties resistant to soil-borne diseases. If you do
not fumigate, the use of resistant varieties for soil-
borne diseases such as wilts should be considered
strongly. Cucumber varieties such as Poinsett
(slicer) and Galaxy picklerr) have high degrees of
resistance to downy mildew, powdery mildew and
other diseases.

XII. Plant Spacing. Crowding plants will allow
moisture from dew or rain to remain on leaf surfaces
longer because of shading and reduced air move-
ment. Such a situation is conducive for disease
development and more frequent spraying with foliar
fungicides may be necessary. Consult Extension
Circular 104 for proper spacing of plants.

After Planting
XIII. Observation. This is an important aspect
of disease control. By observing the garden once a
day you may be able to identify disease problems
early. Many leaf spotting diseases start as just a
few spots on a few leaves and then within a week or
two become uncontrollable epidemics.
XIV. Rogueing. Removing infected plants from
the garden reduces pest populations. Practically
speaking, rogueing will be most beneficial for soil-
borne disease and nematode control if much of the
root system is also discarded. Rogueing plants in-
fected with a root or lower stem disorder will be
beneficial for the current crop and future crops. In
fact, removal of healthy and diseased plants (shoots
and roots) immediately at the end of the season will
be similarly beneficial. Discard such plants or place
them within, not on top of, compost piles, so that
beneficial decomposing organisms can be given an
advantage. Plants left in the garden for one month
after harvest permit nematodes to multiply one
generation, meaning a tenfold increase in their
population rather than a month's decline in popula-
tion. Tillage techniques should be conducted im-
mediately after rogueing.
Rogueing plants that contain a virus is of value if
done at the first sign of mosaic symptoms. Rogue-
ing individual leaves or other plant parts with
fungal or bacterial diseases is not discouraged, but
depending on the disease and weather conditions,
one might gain success after the plant is stripped of
its life-giving organs.

XV. Spraying. No matter how well you fumigate
or conduct previously mentioned control practices,
you may also have to apply a foliar fungicide. Foliar
fungicides will control such disorders as rusts,
mildews, anthracnose and leaf spots. If the
pathogen that is causing leaf disorders also infects
fruit, such fruit infections will also be reduced with a
spray program. Foliar sprays are not effective
against root rots or wilts. Foliar fungicides available
for home owners act as protectants, not eradicants;

thus placement of fungicides on plants prior to infec-
tion is important. Best control of foliar diseases is
done by applying the first spray at the first sign of
disease and repeating the spraying every 7 to 14
days. Shorter spray intervals may be necessary if
the spray program is started late in relation to
disease severity. With experience you can learn
which diseases will appear and when. Foliar diseases
often increase at rapid rates during periods when
temperatures and moisture are favorable for crop
Dusting fungicides are available but sprays are
more effective and safer than dusts. For most
gardens, the use of a one- to five-gallon sprayer-
compressor is adequate. Its maintenance is minimal
provided that it is rinsed with water after every use.
Do not apply a foliar fungicide with a sprayer if it
has not been rinsed with an ammonia solution two
or three times (including lines) after using an her-
bicide. It is best to use one sprayer for herbicides
and one for fungicides.
Hose-attached sprayers can be used but they are
prone to plugging with wettable powder formula-
tions of pesticides. When spraying, use a cone spray
pattern as opposed to a stream spray. One gallon of
water should be used for every 450 square feet. The
use of a commercial spreader-sticker material in the
spray solution is helpful, especially when spraying
waxy leaves such as those of onions, collards, broc-
coli and cabbage. For most other crops it is ade-
quate to place a few drops of household liquid
detergent in each quart of spray. This will help in
"spreading" the water for good initial coverage but
will not enhance sticking ability. If a sticker is used,
spray residues will remain longer and thus spray in-
tervals can be lengthened by a few days. After
heavy rains, it may be necessary to repeat applica-
tions of fungicides.
Cover the entire leaf area with the spray as most
fungicides listed in this publication are not
systemic. Benomyl (Benlate) is systemic to some

Table 2 lists broad spectrum fungicides which are
approved for use on different vegetables. Labels on
various products will vary as to crop listing. Use the
fungicide on a crop for which it is labeled and ac-
cording to the rate listed by the manufacturer.
Table 3 contains some available common broad
spectrum fungicides by trade names. If your garden
shop does not stock these, ask about ordering what
you need; they are available.
Certain other fungicides are available for specific
uses on specific crops. Use rates on the label. Captan
is effective for control of strawberry fruit rots. Basic
copper sulfate (neutral copper, Kocide 101) as a mix
with maneb will control bacterial leaf spots on
tomatoes and peppers. Wettable sulfur is effective
for powdery mildew and rust diseases. Karathane is
effective for powdery mildew control. Benlate
(Benomyl) is an effective fungicide for diseases other
than rusts, downy mildews, Helminthosporium leaf
spots and Alternaria leaf spots.

Table 2. Broad spectrum fungicides for controlling certain
foliar diseases of vegetables.1

Crop Maneb3 Zineb3 Mancozeb3 Chlorothalonil3
Asparagus +4 + +
Beans, blackeyed + +
Beans, lima + +

Beans, snap + + +
Beets +
Broccoli + + +
Brussels sprouts + + +
Cabbage + + +
Carrots + + + +

Cauliflower + + +
Celery + + + +

Table 2. continued
Collards + +

Corn, sweet + + + +

Cucumbers + + + +

Eggplant + +

Endive + +

Kale + +

Kohlrabi + +

Lettuce + +

Melons of all kinds + + + +

Mustard greens + +

Onions + + + +


Peas, English
(green) +
Pepper + +

Potatoes, Irish + + +

Potatoes, sweet

Pumpkins + + +

Radish +

Romaine +

Spinach + +

Squash + + + +

Strawberry +

Tomato + + + +

Turnips + +

1 Label specifies some diseases that are controlled by the
2 Observe the time interval from last spray.application to har-
vest as specified on the label.
3 For powdery mildew diseases this material is not highly ef-
fective. Benlate or Karathane is more effective. See text.
See Table 3 for trade names.
4 Indicates the fungicide is approved for use on the crop as of
May 1984.

Table 3. Trade names and rates of broad spectrum fungi-
cides for controlling foliar diseases of vegetables.1

Common Name Trade Names GALLON2

Maneb Maneb, Manzate D, or 1 1 1/2
(Some with Dithane M-22 Special tblsp3

Zineb Zineb, Zineb 75, 2 tblsp
Dithane Z-78

Mancozeb Dithane M-45 or 1 1/2- 2
Manzate 200 tblsp

Chlorothalonil Bravo 500, 1/2 1 tbisp
L. O. V. Fungicide,
Broad Spectrum Liquid Fungi-
cide, Ortho Vegetable Disease

1 For large garden areas measured in acres, see Extension
Plant Pathology Plant Protection Pointer No. 6 for rates.
2 Use 1 gallon spray per 450 sq. ft.
3 Tablespoons. Rates and crop entrees will vary among labels.
Range listed is based on small package fungicide labels

XVI. Staking and Mulching. Training the vines
of cucumbers, squash, tomatoes and beans to grow
on trellises or wires will help control certain fruit
rots such as belly rot of cucumber, cottony leak of
cucurbits, and fungal fruit rots of tomatoes. The use
of plastic or organic mulch will reduce rots where
fruit develops on the mulch. Both staking and
mulching simply reduce direct contact of fruit with
the soil.
XVII. Petal Plucking. Remove old flower petals
from squash after fruit is set. Wet rot usually begins
on spent petals, and then progresses into the fruit
causing a wet rot with myriads of dark fungal
growths (whiskers).
XVIII. Insect Control. Insects do not cause
plant diseases but they assist by creating wounds.
Fungi and bacteria often enter insect wounds, grow
in the plant, and cause such diseases as root and
stem rots or soft rots of fruit or stems. Thus, insect

control is a control measure for plant diseases. Also,
insects (primarily aphids) transmit certain disease
agents such as viruses. Because transmission of
virus particles from aphids into plants occurs within
seconds, which is faster than insecticides kill
aphids, virus control via insecticide usage is not an
effective approach.

XIX. Watering. The way you water your garden
can influence disease severity of leaf spots, mildews
and rusts. If possible, apply the water to the soil
without wetting the foliage. Use furrow irrigation
on the heavier (non-sandy) and organic soils. Placing
soaker hoses so they discharge the water down in-
stead of up will work well on the lighter (sandy) soils
that are common in Florida. Also, drip irrigation
kits are available. If you irrigate during the middle
of the day, schedule your sprays so that spraying is
done immediately after watering, after leaves have
dried. For other situations spray with a sticker prior
to wetting periods. Pay attention to weather
If you must water with an overhead watering
method, it is best to do so in the late morning to
early afternoon. Excess or insufficient water can
result in plant stress which predisposes plants to
root and stem rots. Watering more often than once
per week may be necessary, especially on sandy
soils. Allowing soils to become dry and then water-
ing reduces yield and produce quality. Variations in
soil from wet to dry can result in more blossom end
rot of tomatoes and peppers even though adequate
calcium is in the soil. Maintain adequate soil
moisture throughout the crop season. With lettuce,
however, reduced water rates minimize root rot. Let-
tuce does not like "wet feet."
Overall, it is best to work in the garden when
foliage is dry to reduce disease spread. Bacterial
diseases are spread effectively by mechanical means
during wet periods.
XX. Post-Harvest Fruit Handling. Avoid rough
handling of produce. Harvest and discard rotted
fruit last. Harvest produce when foliage is dry.

Potatoes should be harvested when soil is not ex-
cessively wet. Do not allow harvested fruit to re-
main in direct sun. Soil adhering to harvested fruit,
tubers, or bulbs should be allowed to dry and then
lightly brushed off. Soaking or washing produce to
remove trash or soil can result in more storage rots
than if not done. If you do wash produce, do not
wash them in water that is cooler than the produce,
and discard blemished produce prior to washing.
Adding bleach to clean wash water for tomatoes and
peppers will reduce bacterial soft rot. Do not allow
fruit to be submerged deeper than 12 inches or for
more than 3 to 4 minutes. Storing produce dry and
within cooled or air conditioned areas will reduce
post-harvest rots. Discard all produce with rot prior
to handling or storage. Periodically, inspect stored
produce'for rot and discard rotted produce.

1. Read the label on each pesticide container
before each use. Heed all cautions and warn-
2. Store pesticides in their original labeled con-
tainers. Keep them out of the reach of children
and irresponsible people.
3. Apply pesticides only as directed.
4. Dispose of empty containers safely.


V'J_ 11

S nWr

This public document was promulgated at a
cost of $5858.06, or 26 cents per copy, to prt
vide information on diagnosis and control ot
plant diseases and nematodes in a home vege-
table garden. 10-26M-84

Tefertiller, 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 p :le
research, educational information and other services only tc (:-i-
duals and institutions that function without regard to rac,:, j... r,
sex or national origin. Single copies of Extension pub ; i.ns
(excluding 4-H and Youth publications) are available free to I ,rria
residents from County Extension Offices. Information on bulk .a :a
or copies for out-of-state purchasers is available from C. M. Hint (
Publications Distribution Center, IFAS Building 664, University ul
Florida, Galnesville, Florida 32611. Before publicizing this public
tion, editors should contact this address to determine availability

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