Blights - Westcott's Plant Disease - page 117

may rot, leaving only the husk and a mass of
black powder. The fungus spreads through the
soil, invading adjacent healthy bulbs.
Control Dig bulbs every year; discard all dis-
eased bulbs and debris; plant in a new location.
Spray with bordeaux mixture.
Mystrosporium adustum (see

large, obovoid, one-celled except for basal
appendage or disjunctor cell; borne singly at
tips of short branches of mycelium forming
a mat over surface of petal tissue (see Fig. 1 ).
Ovulinia azaleae Azalea Flower Spot , Petal
Blight , very destructive to southern azaleas in
humid coastal regions, occasional on mountain-
laurel and rhododendron. Starting as a sudden
outbreak near Charleston, South Carolina, 1931,
the disease spread rapidly north of Wilmington,
North Carolina, down the coast to Florida, and
around the Gulf. It reached Texas by 1938 and
was in California by 1940; it was reported in
Maryland in 1945, in Virginia in 1947, and in
Philadelphia in 1959. Petal blight was reported
from a Long Island, New York, greenhouse in
1956, apparently present there since 1952, and in
1959 infected all the azaleas in one New Jersey
greenhouse. In both cases the blight started on
plants purchased from the South. This is the most
spectacular disease that I have ever witnessed,
with most of the bloom on all the azaleas in
a town blighting simultaneously and seemingly
overnight under special weather conditions. The
blight does not injure stem or foliage; it is con-
fined to the flowers. The loss is aesthetic and
economic from the standpoint of tourist trade.
For many years, before a control program was
worked out, the great azalea gardens of the South
had to close their gates to visitors far too early in
the season.
Primary infection comes from very small
apothecia produced from sclerotia on the ground
under shrubs, usually in January or February,
occasionally as early as December. Spores shot
into the air are carried by wind drift to flowers
near the ground of early varieties, initial spots
being whitish. If you put your finger on such
a spot, the tissue melts away. With continued
high humidity, heavy fog, dew, or rain, conidia
are produced over the inner surfaces of petals and
are widely disseminated to other petals by wind,
insects, and splashed rain. Within a few hours
colored petals are peppered with small white
spots, and white flowers have numerous brown
spots. By the next day flowers have collapsed into
a slimy mush, bushes looking as if they had had
scalding water poured over them. If the weather

Bipolaris
iridis ) . Leaf Blight , Ink Spot of bulbous iris;
also on montbretia and lachenalia.

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Myxosporium

Deuteromycetes, Coelomycetes

Conidia hyaline, one-celled, in discoid to

pulvinate acervuli on branches.
Myxosporium diedickei Twig

Blight of

mulberry.
Myxosporium everhartii Twig Blight of dog-
wood. M. nitidum. Twig blight and dieback of
native dogwood. Prune twigs back to sound
wood; feed and water trees.

Neopeckia

Ascomycetes, Dothideales

Perithecia hairy, not beaked, formed on
a mycelial mass; paraphyses present; spores
two-celled, dark.
Neopeckia coulteri Brown Felt Blight on pines
only, otherwise similar to brown felt blight
caused by Herpotrichia , a disease of high alti-
tudes on foliage under snow.

Ovulinia

Ascomycetes, Helotiales,
Sclerotiniaceae

Stroma a sclerotium, thin, circular to oval, shal-
lowly cupulate, formed in petal tissue but falling
away; minute globose spermatia; apothecia of
Sclerotinia type, small; asci eight-spored;
paraphyses septate with swollen tips; conidia