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RESULTS

(13)

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: Elm

Leaf with small, dark brown lesions and necrosis along veins.

DISEASE: Bacterial leaf spot

HOST: Snapdragon

Leaves with large necrotic areas with brownish centers and purplish margins. Lesions are slightly sunken.

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: Elm leaf scorch

HOST: Elm

Diseased tree with scorch at leaf margins.

DISEASE: Elm leaf scorch

HOST: Elm

Severely diseased tree with dieback and scorched leaves.

DISEASE: Elm yellows

HOST: Elm

Symptoms of elm yellows occasionally appear on one branch before others, but more often they involve the entire crown.

DISEASE: Elm yellows

HOST: Elm

Diseased twig (right) with epinasty, chlorosis, and yellowing of leaves. Sometimes both yellow and green leaves occur on same branch. Healthy branch (left).

DISEASE: Elm yellows

HOST: Elm

Branches with butterscotch discoloration (center) and necrotic flecks in phloem and vascular cambium (right). Healthy branch (left). Sudden wilt and browning is common with small trees.