Tomato Diseases & Abiotic
Problems
Jon Traunfeld
jont@umd.edu
College of
Agriculture and
Natural Resources
Tomato (Solanum lycopersicum)
• Self-pollinating; shrubby annual (temperate
zones) and short-lived perennial (tropics)
• Fruit is 95% water; flavor determined by free
sugars and acids, texture and growing conditions.
• Optimal growth at 70-75°F. mean daily
temperature
• Growth stops below 50°F. Flowers and fruits may
drop when day temperatures >90°F. and night
temperatures >75°F.
• Growth habits vary –determinate, indeterminate,
patio, jointless.
• “What’s the best tomato?” They all grow well in
MD!
Some IPM tips…
• Prevent problems and increase satisfaction by picking at
“breaker” to pink stage. Ripen indoors unrefrigerated.
• People often don’t notice the start of foliar diseases.
• “Wilt” (loss of turgor) is a misused descriptor.
• Don’t suspect late blight unless warranted.
• Disease resistance is variable (field vs. genetic).
• Is it ok to plant in the same location? (common question)
Pick these…
Major tomato plant & pest problems
• Arthropods- spider mites, stink bugs
• Diseases- foliar leaf blights (early blight, Septoria, gray leaf
spot), late blight, fusarium wilt
• Wildlife- mainly deer; also groundhog, squirrel
• Abiotic- poor growing conditions, climate change, blossom-end
rot, catfacing, cracks/splits, pithiness
PLANT DISEASES
Cultural control strategies
• Grow resistant varieties.
• Maintain good air circulation around plants.
• Clean up and compost plant debris at end
of season.
• Prune out injured plant parts.
• Plant lots of flowering plants to attract
beneficial insects.
Disease ID codes help you select resistant hybrid varieties
Totally Tomatoes
Early blight (fungal disease)- tomato
Advanced symptoms of early blight
Early blight- Alternaria solani
• A major foliar disease of tomato; also attacks
potato, eggplant; a cosmopolitan pathogen.
• Splashes up to lower leaves and progresses up
plant; often appears with other leaf spot diseases.
• First symptom is irregular brown lesion with bullseye pattern and yellow halo.
• Can spread rapidly with warm, humid weather
and defoliate plants.
• Over-winters in crop debris, wooden stakes, and
in soil.
Organic management
• Cultivars vary somewhat in susceptibility.
• Give plants more space; improved air
circulation.
• Remove badly infected lower leaves.
• Spray with fixed copper fungicide; other
organic sprays have not proven effective.
Manzate (mancozeb) and Daconil 2787
(chlorothalonil) are chemical fungicides.
Septoria leaf spot… another foliar leaf spot
disease
Cutting or
pruning out
suckers also
increases air
flow around
leaves ,
reducing
disease
incidence.
Late blight – Phytopthora infestans
Late blight fruit
symptoms
Fusarium wilt of tomato
7/30/13
5/14/2013
8/6/2013
9/10/13
9/10/13
Anthracnose- a fungal disease of ripe and
overripe fruit. (Another reason to pick fruit at the
“turning” stage).
ABIOTIC PROBLEMS
Frost/cold injury- leaf
whitening, small
gray/brown spots, or
blotches
Phosphorous
deficiency early in
season due to cool soil
and small root system
Edema- excessive soil
moisture early in
season, especially in
containers.
Blossom drop due to environmental stress
(usually high temp.). Photo courtesy: Jerry Brust, Ph.D.
Clopyralid
herbicide
injury
2,4-D herbicide
injury
Blossom-end rot
(nutritional disorder)
Epsom salt is NOT the
answer.
Muskmelon leaf
burned with
pyrethrum and
soap insecticide
“Catfacing”
Adventitious
(aerial) roots
Physiological leaf roll (heat stress)
Concentric cracking
Radial cracking
Graywall (blotchy
ripening); inside fruit
walls are brown or
black
Pithinessexcessive white
tissue
Green shoulder
Uneven ripening
Zippering
Garden located
next to large
driveway that was
resurfaced. Injury
from petroleum
products coming
off “liquid asphalt
cement”
Weird stuff…
ENJOY!
Resources
• Grow It! Eat It!
http://www.extension.umd.edu/growit
– We have all types of practical food gardening tips and
information. Check out our popular blog!
• Home and Garden Information Center
http://www.extension.umd.edu/hgic
– Here you will find factsheets, photos, and videos. You
can also subscribe to the free monthly e-newsletter.
– We answer gardening questions 24/7…just click
“Ask Maryland’s Garden Experts”
• Maryland Master Gardener Program
http://www.extension.umd.edu/mg
– Consider becoming a trained MG volunteer!
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