Plant disease & disorder profiles
Showing 10 of 74 profiles: symptoms, spread, host crops, and organic-first treatments.
Angular leaf spot
Pseudomonas syringae pv. lachrymans
A bacterium that produces angular, vein-bound spots on cucumber and melon leaves, often leaking a sticky ooze that dries into a white crust.
- Hosts
- Cucumber, Cantaloupe / Melon, Zucchini, Winter squash
Bacterial spot
Xanthomonas spp.
A seed- and splash-borne bacterium that riddles tomato and pepper leaves and fruit with small, scabby dark spots. Unlike fungal spots it has no rings and no fuzzy growth, just a greasy, water-soaked look at first.
- Hosts
- Tomato, Pepper
Bacterial wilt of cucurbits
Erwinia tracheiphila
A bacterium spread almost exclusively by cucumber beetles, which introduce it while feeding. It clogs the plant's water-conducting vessels, causing a sudden, irreversible wilt.
- Hosts
- Cucumber, Cantaloupe / Melon, Zucchini, Winter squash
Black rot (grape)
Guignardia bidwellii
A fungal disease specific to grapes that produces reddish-brown leaf spots and then completely mummifies developing berries into hard, black, wrinkled raisins.
- Hosts
- Grape
Downy mildew (cucurbit)
Pseudoperonospora cubensis
A wind-dispersed water mold that produces angular, vein-bound yellow spots on the top of cucumber and melon leaves with a fuzzy gray-purple mold visible underneath.
- Hosts
- Cucumber, Cantaloupe / Melon, Watermelon, Zucchini
Frost / chill injury
N/A — abiotic (cold temperature injury)
Ice formation inside plant cells (frost) or prolonged cold below a crop's tolerance (chilling, even above freezing for warm-season crops) ruptures cells and disrupts normal metabolism.
- Hosts
- Tomato, Pepper, Zucchini, Cucumber
Fusarium crown and root rot
Fusarium oxysporum f. sp. radicis-lycopersici (and related formae)
A close relative of Fusarium wilt that attacks the crown and root system rather than moving up the whole vascular system, causing a brown, sunken canker right at the soil line.
- Hosts
- Tomato, Cucumber, Watermelon
Halo blight
Pseudomonas savastanoi pv. phaseolicola
A bean-specific bacterium that produces small angular spots ringed by a wide, pale-green-to-yellow halo, often larger than the spot itself.
- Hosts
- Bush bean, Pole bean
Herbicide drift injury
N/A — abiotic (chemical injury)
Herbicide applied nearby (on a lawn, roadside, or neighboring field) drifts on wind or volatilizes in heat and lands on garden plants, causing characteristic twisting and cupping, especially from broadleaf herbicides like 2,4-D or dicamba.
- Hosts
- Tomato, Pepper, Grape
Phytophthora blight
Phytophthora capsici
A soil- and water-borne mold that causes sudden crown collapse and a fast-spreading fruit rot, especially devastating in low or poorly drained spots after heavy rain.
- Hosts
- Pepper, Zucchini, Winter squash, Pumpkin
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