1. Advanced Tomato Workshop
Common Tomato Problems
Chris Becker

2. Insect, Disease, or Disorder?
Tomato Problem Quiz Answers
Insect, Disease, or Disorder?

3. 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.

4. Diseases Abiotic Biotic
Abiotic diseases are caused by non-living environmental conditions such as frost, hail, and chemical burn, nutrient deficiencies.
Biotic diseases are caused by living organisms.
Biotic causes of disease include fungi, bacteria, viruses, phytoplasmas, nematodes, and parasitic plants.

6. Disease Symptoms
Symptoms of disease are the plant’s reaction to the causal agent.
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.
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.

7. Disease Signs Signs are the actual organisms causing the disease.
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.
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.

8. #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

9. #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

10. #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

11. #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.

12. #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

13. #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

14. #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.

15. #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.

16. #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

17. #10 Blossom End-Rot A Nutrient Disorder
Caused by a Calcium Deficiency,
Due to improper soil pH, above or
below
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.

18. #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 first-
formed fruit.
Common in the large-fruited
“beefsteak” type tomatoes.
Prevention
none

19. #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

20. #13 Stinkbugs An Insect Pest Feed with piercing-sucking
mouthparts which cause whitish-
yellow 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

21. #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

22. #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

23. #16 Armyworms Insect Pest Caterpillar color varies from dull
green to black.
Older larvae have a broad, light-
colored 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

24. #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

25. #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.

26. #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

27. #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

28. #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.

29. #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.

30. #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

31. #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

32. #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

33. #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.

34. #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

35. #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

36. #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

37. #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.