Plant disease & disorder profiles
Showing 24 of 74 profiles: symptoms, spread, host crops, and organic-first treatments.
Bacterial canker
Clavibacter michiganensis subsp. michiganensis
A systemic tomato bacterium that moves inside the plant's vascular system, causing one-sided wilting, stem cankers, and a telltale 'bird's-eye' spot on fruit.
- Hosts
- Tomato
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 of brassicas
Xanthomonas campestris pv. campestris
A vascular bacterium of cabbage-family crops that enters through leaf edges and water pores, causing distinctive V-shaped yellow wedges that point toward the leaf's blackened veins.
- Hosts
- Cabbage, Broccoli, Cauliflower, Kale
Brown rot
Monilinia fructicola
A fast-moving fungus that blights blossoms in spring and then rots ripening stone fruit into a soft brown mass covered in gray-tan powdery spore tufts, often spreading fruit to fruit where they touch.
- Hosts
- Peach, Plum, Cherry
Clubroot
Plasmodiophora brassicae
A soilborne organism (technically a protist, long grouped with fungal diseases) that infects brassica roots and causes grotesque, swollen, club-shaped galls that cripple water and nutrient uptake.
- Hosts
- Cabbage, Broccoli, Cauliflower, Kale
Curly top virus
Beet curly top virus (BCTV)
A leafhopper-vectored virus common in hot, dry western regions that causes dramatic upward leaf curling, stunting, and often plant death, especially on tomato and bean.
- Hosts
- Tomato, Pepper, Bush bean
Fire blight
Erwinia amylovora
A fast-moving bacterium of apples, pears, and their relatives that scorches blossoms, shoots, and branches so they look burned, giving the disease its name.
- Hosts
- Apple, Pear
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
Fusarium wilt
Fusarium oxysporum (host-specific formae speciales)
A soilborne fungus that invades roots and clogs the plant's water-conducting tissue from the inside, causing one-sided or whole-plant wilting that doesn't recover even with watering.
- Hosts
- Tomato, Watermelon, Cantaloupe / Melon, Pepper
Heat-induced blossom drop
N/A — abiotic (heat stress on pollen viability)
When nighttime temperatures stay too warm or daytime heat spikes too high, pollen becomes sterile or fails to release properly, so flowers form but abort and drop without setting fruit.
- Hosts
- Tomato, Pepper, Bush bean
Overwatering / root suffocation
N/A — abiotic (waterlogging, oxygen deprivation)
Saturated soil pushes air out of the pore spaces roots need to breathe, so roots suffocate and die even though the plant looks like it's drowning in symptoms that mimic drought.
- Hosts
- Tomato, Pepper, Cucumber, Bush bean
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
Phytophthora root rot
Phytophthora spp.
A general term for water-mold root rots affecting perennials and fruiting shrubs/trees planted in soil that stays wet, slowly killing the root system from the tips inward.
- Hosts
- Strawberry, Raspberry, Blueberry, Apple
Rhizoctonia root and crown rot
Rhizoctonia solani
A very common soil fungus that attacks seedlings at the soil line (a major cause of damping off) and, in older plants, causes root/crown rot and — on potato — the black, tar-like 'black scurf' on tubers.
- Hosts
- Bush bean, Potato, Cabbage, Lettuce
Ring rot of potato
Clavibacter sepedonicus
A quarantine-significant potato bacterium that plugs the vascular ring inside the tuber with a cheesy, cream-colored rot, usually spread from infected seed potatoes rather than the field.
- Hosts
- Potato
Root-knot nematode
Meloidogyne spp.
A microscopic soilborne roundworm that burrows into roots and triggers swollen galls as the plant's cells are hijacked to feed the nematode. Above-ground symptoms mimic drought or nutrient stress, which makes it easy to misdiagnose without pulling a plant.
- Hosts
- Tomato, Carrot, Cucumber, Pepper
Salt burn
N/A — abiotic (salt toxicity)
Excess soluble salts in the soil, from over-fertilizing, road salt runoff, or naturally saline soil/water, pull moisture out of roots and scorch leaf margins.
- Hosts
- Lettuce, Bush bean, Carrot, Strawberry
Soil compaction stress
N/A — abiotic (physical root restriction)
Repeated foot traffic, tilling wet soil, or heavy equipment presses soil particles together, squeezing out the pore space roots need to grow and water needs to drain through.
- Hosts
- Carrot, Potato, Tomato, Bush bean
Southern blight
Sclerotium rolfsii
A fast, heat-loving soil fungus that girdles the stem right at the soil line, identifiable by a white fan of fungal threads and mustard-seed-sized round sclerotia at the plant's base.
- Hosts
- Tomato, Pepper, Bush bean, Watermelon
Tomato spotted wilt virus
Tomato spotted wilt virus (TSWV)
A thrips-vectored virus with a very wide host range, causing bronzing, ring spots, and stunted, one-sided growth. Once thrips introduce it, there's no cure.
- Hosts
- Tomato, Pepper, Lettuce
Transplant shock
N/A — abiotic (root disturbance stress)
Moving a plant from a container or one location to another damages fine roots and abruptly changes light, temperature, and moisture, so the plant wilts and stalls until new roots establish.
- Hosts
- Tomato, Pepper, Lettuce, Cabbage
Verticillium wilt
Verticillium dahliae
A cool-weather cousin of Fusarium wilt with an enormous host range (over 200 plant species), clogging the vascular system and producing distinctive V-shaped yellow wedges on leaves.
- Hosts
- Tomato, Potato, Eggplant, Pepper
White mold (Sclerotinia)
Sclerotinia sclerotiorum
A fungus that infects through dying blossoms, then colonizes stems and pods with a fluffy white cotton-like growth studded with hard black sclerotia the size of mouse droppings.
- Hosts
- Bush bean, Zucchini, Winter squash, Cabbage
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