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RESULTS

(45)

DISEASE: Alfalfa dwarf

HOST: Alfalfa

Alfalfa dwarf is characterized by stunted plants (left), usually dark blue-green in color. Xylem tissues become brown, especially when exposed to air.

DISEASE: Angular leaf spot

HOST: Tobacco

Leaf with light brown, angular spots. The difference between this disease and wildfire of tobacco is that wildfire is caused by a strain that produces tabtoxin. It causes conspicuous halos around lesions and large parts of a leaf may turn yellow .

DISEASE: Angular leaf spot

HOST: Tobacco

Yellowing of adjacent tissues occur as spots age (midseason). It causes conspicuous halos around lesions. Large parts of a leaf may turn yellow.

DISEASE: Angular leaf spot

HOST: Tobacco

Severely diseased leaf with extensive yellowing.

DISEASE: Aster yellows

HOST: Onion

Infected plants with yellowish, malformed leaves.

DISEASE: Aster yellows

HOST: Onion

Onion flower with unusual symptoms (left) compared with healthy inflorescence (right). Flowers are distorted and often have abnormally long pedicels. Young leaves may have yellow streaks or a general yellowing of basal portions.

DISEASE: Bacterial fasciation (Leafy gall)

HOST: Tobacco

Bacterial fasciation of tobacco.

DISEASE: Bacterial flower stalk and leaf necrosis

HOST: Onion

Dark, rotted areas of stalk and leaves caused by systemic invasion of the pathogen.

DISEASE: Bacterial flower stalk and leaf necrosis

HOST: Onion

Gray-brown rot of onion after inoculation. Disease starts as small, water-soaked lesions that later develop into slimy, gray-brown rot. The disease progresses downward from the stalk and may rot the entire bulb.