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RESULTS

(16)

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 fasciation (Leafy gall)

HOST: Begonia

Leafy gall on stem.

DISEASE: Bacterial leaf spot (Blight)

HOST: Begonia

Initial symptoms appear as small, blisterlike lesions. As lesions age, they enlarge, producing broad patches of necrotic leaf tissue.

DISEASE: Bacterial leaf spot (Blight)

HOST: Begonia

Advanced stage of disease with dark, large necrotic areas on leaves and interveinal chlorosis.

DISEASE: Bacterial leaf spot (Head rot)

HOST: Lettuce

Leaf with black, greasy spots that tend to be vein delimited. Lesions begin as small, angular, water-soaked lesions that coalesce, resulting in large necrotic areas.

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: Corky root

HOST: Lettuce

Corky root causes a reduction in size of lettuce heads and root systems; susceptible cultivar (right) and resistant cultivar (left).

DISEASE: Corky root

HOST: Lettuce

Close-up of root with malformed, corky appearance and longitudinal ridges of brown tissues.

DISEASE: Corky root

HOST: Lettuce

Initial symptoms of disease are yellow lesions on taproot and main laterals. Greenish brown bands occur around roots. Root pith may become brown and hollow.