|Disease (causal agent)
||Survival of pathogen and effect of environment
||Comments on control
|Soft, light brown galls up to 2 inches (5 cm) in diameter develop at or below soil line. Galled plants are often stunted and some die.
||Bacteria survive in galls and in aerial parts of the plant. Infection is favored by warm conditions.
||Use pathogen-free stock developed
through tissue culture. Avoid wounding plants when establishing field plantings. Maintain strict sanitation in propagation.
|Infected flowers turn black.
||Favored by moist conditions.
||Avoid overhead irrigation during
flowering. Protective sprays of iprodione or chlorotholonil may be helpful in severe situations.
|Phytophthora crown rot
|Leaves wilt and turn light green. Entire plant may collapse
and die. Crown tissue is discolored and a soft, wet decay develops. Secondary bacteria cause the diseased tissue to putrefy.
||Pathogen is soilborne and may be present in many fields.
Disease is favored by warm temperatures 90°F, moist conditions, and poor drainage.
||Improve drainage by planting on
raised beds. Do not moisture‑stress plants, but do not overwater. Soil
drenches of mefenoxam are helpful in preventing the disease. more info *
|Soft wet decay of seedlings and plants in propagation. Leaves
of infected plants turn grey‑green. In the field, roots are rotted and plants are stunted.
||Several species of Pythium are involved. Pythium aphanidermatum is favored by warm or hot conditions while P. ultimum develops at lower temperatures. Both pathogens are present in many field soils. Disease is favored by overwatering and poor drainage.
||Mefenoxam is helpful when used in
preventative programs. more info *
|All stages of growth may be affected. Stems are infected at or
just beneath the soil line. Sunken dark lesions are dry in the early stages but later the decay becomes soft and wet.
||Fungus occurs naturally in many soils. Favored by warm, wet conditions and deep planting.
||Treat soil or planting medium with
granular PCNB before planting. Avoid deep planting. Spray base of plants before or after planting with iprodione or PCNB. Keep PCNB off foliage.
is also susceptible to gray mold * (Botrytis cinerea), bacterial fasciation (Rhodococcus fascians),
root knot nematode** (Meloidogyne spp.), cottony
rot * (Sclerotinia sclerotiorum), southern
blight * (Sclerotium rolfsii), crown
gall * (Agrobacterium tumefaciens), and aster yellows * (aster yellows phytoplasma).
|* For additional information, see section on Key Diseases.
|** For additional information, see section on Nematodes.