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RESULTS

(14)

DISEASE: Aster yellows

HOST: Barley

Infection by this phytoplasm causes twisted awns and sterile florets.

DISEASE: Aster yellows

HOST: Barley

Small necrotic spots on lower leaves and red coalescing streaks on upper leaves.

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 kernel blight (Leaf blight)

HOST: Barley

Dark, brown discolored kernels at the embryo end and posterior surface.

DISEASE: Bacterial leaf blight

HOST: Barley

Diseased barley plants with typical bleaching of flag leaves. Initial symptoms are water-soaked lesions that later coalesce. Eventually, the entire leaf becomes necrotic and edges roll inward.

DISEASE: Bacterial stem and root rot

HOST: Sweet potato

Collapse of stems and roots caused by systemic activity of the pathogen.

DISEASE: Bacterial stem and root rot

HOST: Sweet potato

Rot and collapse of stem, petioles, and leaves caused by systemic infection.

DISEASE: Bacterial stem and root rot

HOST: Sweet potato

Rot and internal discoloration of tuber.

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.