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RESULTS

(6)

DISEASE: Aster yellows

HOST: Squash

Diagnostic characteristics for the disease are yellowing of young leaves, proliferation of secondary shoots, and rigid erect habit. Leaves are misshapen and smaller than normal and have stiff, thick laminae.

DISEASE: Bacterial leaf spot

HOST: Larkspur

Infected leaflets with many purplish spots with necrotic centers.

DISEASE: Bacterial wilt

HOST: Squash

Field with severe symptoms of wilt. Foliage often is chlorotic and leaf margins may be chlorotic and necrotic before plant death. Bacterial ooze may be seen streaming from the xylem when infected stems are cut.

DISEASE: Black chaff (Bacterial leaf streak)

HOST: Wheatgrass

Lesions on leaves first appear as water-soaked, translucent, long, narrow streaks. They later turn brown and necrotic and often coalesce into blighted areas.

DISEASE: Black chaff (Bacterial leaf streak)

HOST: Wheatgrass

Close-up of leaf with brown necrotic streaks.

DISEASE: Larkspur virescence

HOST: Larkspur

Two diseased plants with stunted and small leaves, lack of flower coloration, and bunched flower buds. Healthy plant (left).