Advanced Tomato Workshop
Common Tomato Problems
Chris Becker
Tomato Problem Quiz Answers
Insect, Disease, or Disorder?
What is a Disease?
• A plant disease is usually defined as
abnormal growth and/or dysfunction of a
plant. Diseases are the result of some
disturbance in the normal life process of the
plant
• Diseases may be the result of living and/or
non-living causes.
Diseases
Abiotic
• Abiotic diseases are
caused by non-living
environmental conditions
such as frost, hail, and
chemical burn, nutrient
deficiencies.
Biotic
• Biotic diseases are
caused by living
organisms.
• Biotic causes of disease
include fungi, bacteria,
viruses, phytoplasmas,
nematodes, and parasitic
plants.
Disease Symptoms
Symptoms of disease are the plant’s reaction to the
causal agent.
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Blight – A rapid discoloration and death of twigs,
foliage, or flowers.
Canker – Dead area on bark or stem, often
sunken or raised.
Chlorosis – yellowing – Chlorosis is so generic
that without additional details diagnosis is
impossible.
Decline – Progressive decrease in plant vigor.
Dieback – Progressive death of shoot, branch or
root starting at the tip.
Distortion – malformed plant tissue.
Gall or gall-like – Abnormal localized swelling or
enlargement of plant part. It could be caused by
insects, mites, diseases, or abiotic disorders.
Gummosis – Exudation of gum or sap.
Leaf distortion – The leaf could be twisted,
cupped, rolled, or otherwise deformed.
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Leaf scorch – Burning along the leaf margin and
into the leaf from the margin.
Leaf spot – A spot or lesion on the leaf.
Mosaic – varying patterns of light and dark plant
tissue.
Necrosis – dead tissue – Necrotic areas are also
so generic that without additional details diagnosis
is impossible.
Stunting – lack of growth.
Wilt – General wilting of the plant or plant part.
Witches broom – Abnormal broom-like growth of
many weak shoots.
Insect feeding injury is also a symptom used in
diagnosis, but not a symptom of disease.
Disease Signs
Signs are the actual organisms causing the
disease.
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Conks – woody reproductive structures
of fungi.
Fruiting bodies – Reproductive
structures of fungi; could be in the form
of mushrooms, puffballs, pycnidia,
rusts, or conks.
Mildew – whitish growth produced by
fungi composed of mycelium.
Mushrooms – fleshy reproductive
structures of fungi.
Mycelium – thread-like vegetative
growth of fungi.
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Rhizomorphs – Shoestring-like fungal
threads found under the bark of
stressed and dying trees caused by the
Armillaria fungi. They may glow in the
dark!
Slime Flux or Ooze – A bacterial
discharge that oozes out of the plant
tissues, may be gooey or a dried mass.
Spore masses – masses of spores,
the “seeds” of a fungus.
Insects and/or their frass (excrement)
are also signs, although not signs of
disease.
#1 Aphids
 Insect Pests
 Have piercing, sucking mouthparts;
physical damage not always apparent
 Usually found on underside of leaf
 They can reproduce asexually.
 Color varies in species
 Produce honeydew
Prevention
 Insecticides
#2 Fruit Cracking/Splitting
 An Environmental Disorder
 Caused by rapid fruit development
and wide fluctuations in water
availability to the plant.
 Mature ripening fruit are most
susceptible, especially when there
is a very dry period followed by
heavy rainfall.
 Severity varies greatly by variety.
Prevention
 incorporate organic matter, use
drip irrigation, apply mulch
#3 Septoria Leaf Blight
 A Fungal Disease
 Causes numerous small ( about
1/8" to 1/4" in diameter) brown
spots that develop light tan to
white center as they age
 Similar to early blight. Attacks
older leaves – turns yellow,
brown, then withers and dies.
 Wet humid conditions favor the
development .
 It usually appears after plants
begin to set fruit.
Prevention
 use mulch, apply fungicide, limit
wetting foliage / overhead watering
#4 Herbicide Damage
 Herbicide Damage
 Symptoms include downward
rolling of leaves and twisted
growth. In addition, stems may
turn white and split; fruit may be
deformed.
 Depending on the level of
exposure, the plant may or may
not survive.
Prevention
 Do not apply 2-4-D like herbicides
near the garden
 Avoid drift
 Prevent contamination by
keeping herbicide spray tanks
separate from insecticide
& fungicide spray tanks.
#5 Glyphosate Injury
 Herbicide Damage
 White/Yellow discoloration at the
base of the youngest leaflets.
 A result of spray drift to the stem
of the plant and/or application
during a windy day.
 Herbicide on stem becomes
translocated to the upper leaves.
 1/50th to 1/150th rate can do this
type of damage.
Prevention
 Use a shield to limit drift.
 Cut off the leaves and observe the
plant
#6 Southern Blight
 A Soilborne Fungal Disease
 Causes yellowing of leaves and
wilting of infected plants.
 The stem at the soil line appears
soft and sunken (cankered) and
turns brown to black.
 Under moist conditions, a white
fungal growth occurs on the lower
stem near the soil surface.
 Favored by moist conditions and
high temperatures above 85 °F.
Prevention
 crop rotation, soil solarization,
deep plowing
#7 Fusarium Wilt
 A Soilborne Fungal Disease
 Invades the roots, plugs-up the
water conducting vessels, causes
yellowing and wilting of leaves.
 Initially causes a yellowing and
wilting of lower leaves on a single
branch.
 Whole plant eventually wilts and
dies.
Prevention
 use resistant varieties, crop
rotation, soil solarization.
#8 No Tomatoes
 Mostly an Environmental Disorder
 Plants sometimes drop their flowers
when night temperatures are lower
than 55°F.
 When night temperatures above
70°F, flower production and
pollination are reduced.
 Favorable night range for tomato
fruit set is between 58 and 68°F.
 Very hot daytime temperatures
coupled with drought is a cause too.
 May occur due to excessive nitrogen.
Prevention
 Use heat resistant varieties.
#9 Tomato Fruitworm
 Insect Pest
 Also known as Corn Earworm
 Caterpillar color varies from light
green to reddish-brown.
 Usually has a broad dark stripe
with a light stripe on the body.
 Feeds on stem end, entering
inside the fruit of green tomatoes.
 Feeding damage leads to watery
and wormy fruit.
Prevention
 Hand Remove
 Insecticides
#10 Blossom End-Rot
 A Nutrient Disorder
 Caused by a Calcium Deficiency,
 Due to improper soil pH, above or
below 6 - 6.5.
 Insufficient calcium in soil
 Aggravated by changes in soil
moisture – too dry or too wet
Prevention
 spray calcium nitrate for temporary
relief, take a soil test, add lime,
keep soil moisture consistent.
#11 Catfacing
 A Physiological Disorder
 Misshapen ugly fruit.
 Cold weather at the time of
blossom set distorts and kills
certain cells that should develop
into fruit, resulting in the
deformities.
 Most often observed among firstformed fruit.
 Common in the large-fruited
“beefsteak” type tomatoes.
Prevention
 none
#12 Zippering
 A Physiological Disorder
 A thin longitudinal scar from the
stem scar to the blossom end.
 Series of transverse scars which
resemble a zipper.
 This defect happens when the
flower anthers fuse to the ovary
wall of developing fruit
 Occurs most commonly when fruit
set takes place in cool weather.
 Varieties can vary in their
susceptibility to this malady.
Prevention
 None
#13 Stinkbugs
 An Insect Pest
 Feed with piercing-sucking
mouthparts which cause whitishyellow corky spots underneath the
skin of the fruit.
 On green fruit, damage appears as
dark pinpricks surrounded by a
light discolored area
 Commercially, this damage is
serious because they render the
fruit unmarketable.
Prevention
 Insecticides
#14 Early Blight
 A Fungal Disease
 Begins on older lowers leaves by
turning them yellow.
 Leads to irregular spots that
enlarge to ½ inch in diameter with
concentric rings and a yellow halo.
 Plants appear to “fire-up” from
their base
 Early season pest; warm, wet
weather favor its development
Prevention
 use mulch, apply fungicide, limit
wetting foliage / overhead watering
#15 Tomato Spotted Wilt Virus
 Virus disease spread by thrips
 Infected plants are stunted, may
die slowly.
 Dark ring spots form on leaves.
 Terminal leaves stop growing,
become distorted and have a pale
purple/bronze appearance.
 Fruit exhibit “real cool-looking”
ringspots.
Prevention
 Remove suspected and infected
plants immediately, control insects,
use resistant varieties
#16 Armyworms
 Insect Pest
 Caterpillar color varies from dull
green to black.
 Older larvae have a broad, lightcolored stripe along the side of
the body.
 Feeds primarily on leaves but will
attack fruit making a single or
group of holes or depressions.
 Damage is typically superficial but
could lead to fruit to rot.
Prevention
 Hand Remove
 Insecticides
#17 Leaf Roll
 A Physiological Disorder
 Edges of the leaves roll upward
and inward.
 High temperatures, prolonged
periods of wet soil conditions,
and drought may promote
symptom development.
 Symptoms are most common
when plants have a heavy fruit set.
 Associated with varieties having a
specific gene that favors this condition.
Prevention
 Variety Selection, Irrigation
#18 Cutworms
 An Insect Pest
 Active only at night and remain
buried below the soil surface near
food plants during the day.
 They emerge to feed at night and
often cut seedlings or small
stems, causing the plants to fall
over.
Prevention
 Insecticides, remove grass and
weeds, plow the soil well in
advance of planting, use paper or
plastic "sleeve" over the plant to
protect the stem.
#19 Sunscald
 A Physiological Disorder
 Initial symptom is a whitish, shiny
area that appears blistered.
 Occurs on green tomato fruit
exposed to the sun.
 Injury is more serious during
periods of abnormally high
temperatures.
 The killed tissue is quickly
invaded by secondary organisms
and the fruit decays.
Prevention
 Control foliar diseases
 Avoid heavy pruning
#20 Bacterial Spot and Speck
 Bacterial Diseases
 Introduced on transplants
 Attacks leaves and fruit
 Favored by warm, wet conditions
 Leaf spots can be irregular and
ragged
 Fruit spots can be raised or
scabby
Prevention
 Use disease-free transplants
#21 Tobacco Hornworm
 Insect Pest
 Large, smooth, green caterpillar of
the Carolina Sphinx moth.
 Mature larvae measure 3½” in
length
 Has seven or eight conspicuous
white V-shaped markings down
each side and a prominent spike
(horn) on its rear end
 Feeds on the leaves, stems and
fruit of tomato plants
Prevention
 Hand remove, insecticides, plant
dill a trap crop.
#22 Adventitious Roots
 A Physiological Disorder
 These are adventitious roots or
aerial roots which would grow into
normal roots if placed in contact
with the soil.
 They emerge as a result of stress,
particularly water-related stress.
 Determined by cultivar, weather
conditions and culture.
Prevention
 Maintain moisture, mound
compost around root initials on
the lower part of the plant.
#23 Thrips
 Tiny Insect Pests
 Prefer to feed in flowers, but also
occur in flower and leaf buds and
on leaves.
 Feeding on foliage may cause a
bronzing or silvering of foliage.
 Eggs inserted in fruit causes
dimpling, and the infested area
may appear white.
 Thrips are also vectors of tomato
spotted wilt virus.
Prevention
 Insecticides
#24 Whiteflies
 An Insect Pest
 Adults are very small, white and
moth-like; 1/16th inch long.
 Feed underside the leaves on plant
sap.
 Usually noticed during mid to late
summer.
 Numbers are usually not sufficient
to cause damage to plants.
 They do excrete honeydew and
may cause sooty mold.
Prevention
 Insecticides, sticky traps
#25 Spidermites
 An Arachnid Pest
 They damage plants by inserting
their stylet mouthparts into
individual plant cells and
withdrawing cellular liquids and
contents.
 Damaged plants take on a bronzed
appearance.
 Affected leaves eventually die and
turn brown.
 Tends to be hot weather pest.
Prevention
 Horticultural oils and soaps
#26 Bacterial Wilt
 A Soilborne Bacteria Disease
 Most commonly found in low, wet
areas of fields.
 Plants wilt and die rapidly without
yellowing or spotting of the
foliage.
 It invades and gradually blocks
the vascular tissue (the food- and
water-conducting vessels just
beneath the epidermis).
 The pith will turn brown and
sometimes become hollow.
Prevention
 crop rotation, soil solarization.
#27 Nematodes
 Microscopic wormlike animals
found in the soil – 1 mm in length.
 Damage plants by feeding on
roots, impairing its ability to
take up water and nutrients.
 Cause stunting, leaf yellowing,
loss of plant vigor, reduction in
yields, and wilting.
 Causes distinct swellings or galls
on roots.
 Non-uniform distribution of
symptomatic plants
Prevention
 Soil Solarization, Crop Rotation
#28 Flea Beetle
 Flea beetles are tiny black beetles
that jump when disturbed.
 Overwinter as adults and begin
feeding in spring.
 Feed on the undersides of leaves
causing small holes or sunken
pits.
 Mostly a problem on new
seedlings, and if left unchecked,
can cause significant
Prevention
 Insecticides
#29 Leaf-footed bug
 Insect pest that feeds on tomato
plants during the adult and nymph
stage.
 Overwinter as adults and begin
feeding in spring.
 Congregate and feed together
during nymph stages.
Prevention
 Insecticides
#30 Buckeye Rot
 Caused by the fungus
phytophthora parasitica.
 Starts as a grayish green or
brown
spot on fruit that has come into
contact with soil.
 Light and dark brown concentric
bands appear in the affected area.
This firm, leathery rot is
characterized by a smooth
surface and lack of sharply
defined margins.
Prevention
 Mulch, prevent fruit from
touching the soil.