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RESULTS

(8)

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 blight (Angular leaf spot)

HOST: Cotton

Leaf with advanced stage of blight.

DISEASE: Bacterial blight (Angular leaf spot)

HOST: Cotton

Highly susceptible (left) and resistant (right) cotton cultivars. The black arm stage of the disease is the most serious and occurs when bacteria invade petioles and then stems.

DISEASE: Bacterial blight (Angular leaf spot)

HOST: Cotton

Characteristic early symptoms are water-soaked leaf spots and water-soaking along veins.

DISEASE: Bacterial blight (Angular leaf spot)

HOST: Cotton

Leaf with dark, angular leaf spots. Systemic invasion causes blackening of midribs.

DISEASE: Bacterial blight (Boll rot)

HOST: Cotton

Boll rot first appears as raised, water-soaked lesions, which become sunken and turn brown to black with time.

DISEASE: Bacterial blight (Boll rot)

HOST: Cotton

Infection of bolls causes premature opening and increased susceptibility to secondary, saprophytic microorganisms that cause rot. Note discolored cotton.

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.