Biology Reference
In-Depth Information
flesh is not affected, but the cracks furnish
entrance to anthracnose and other decay organ-
isms. The fungus winters in leaves, and appears to
be progressively more abundant.
Gloeodes pomigena Sooty Blotch of Fruit on
apple, crabapple, blackberry, pear, and citrus, in
eastern and central states down to the Gulf, rare in
the West. Fruit may be infected by heavy spore
dissemination from pycnidia on twigs of various
wild trees, including persimmon, prickly-ash,
white ash, bladdernut, hawthorn, red elm, sassa-
fras, maple, sycamore, and willow. On apples,
clusters of short dark hyphae make a superficial
thallus on the cuticle, which appears as a sooty
brown or black blotch, 1/4 inch in diameter.
Numerous spots may coalesce to cover the
apple, a condition known as cloudy fruit. Because
the lesion is superficial the fruit flesh is little
affected, but the grade and market value are
reduced. On citrus the fungus does not penetrate
the rind, and spots can be removed by gentle hand
rubbing. The disease develops in cool rainy
weather during the summer. To control open up
the trees in the orchards to facilitate quick drying.
Cladosporium
Deuteromycetes, Hyphomycetes
Conidiophores dark, branched variously near
upper or middle portion, clustered or single;
conidia dark, one-or two-celled, variable in size
and shape, ovoid to cylindrical, borne singly or in
chains of two or three; parasitic or saprophytic.
Cladosporium herbarum Leaf Blotch of
lilac. The fungus is usually secondary, sapro-
phytic, following blights.
Cladosporium paeoniae Peony Leaf Blotch ,
Red Stem Spot , Measles . Leaf and stem spots
are purplish or brownish red. On stems the spots
are raised, upto 4 mm long; on leaves the lesions
are small specks. Small reddish spots are also
present on floral bracts and petals. The disease
is widely distributed in commercial plantings and
may sometimes destroy the value of flowers for
cutting. Cut down tops in fall as for Botrytis
blight. Spraying the ground with Elgetol in spring
before new growth starts has given good control
in some fields.
Guignardia
Ascomycetes, Dothideales
Perithecia immersed in substratum, stroma
lacking, mouths papillate; spores hyaline
unequally two-celled, with lower cellcut off just
before maturity.
Guignardia aesculi Horse-Chestnut Leaf
Blotch , Buckeye Leaf Blotch , general on horse-
chestnut and Ohio buckeye, sometimes on red
and yellow buckeye. Large, reddish brown
blotches in foliage are, usually, surrounded by
a yellowish area. Numerous pin-point black
dots, pycnidia, distinguish blotch from scorch
due to drought. Petioles often have reddish oval
spots. In a rainy season there is a good deal of
secondary infection from spores spread by wind
and rain. Blotches appear on nearly every leaflet
with extensive defoliation. Primary infection in
spring comes from ascospores developed in
fallen overwinter leaves.
Control Rake up and burn leaves in fall. Feed
trees that have been defoliated for successive
years.
Geastrumia
Geastrumia polystigmatis Sooty Blotch of
Fruit on apple and blackberry.
Gloeodes
Deuteromycetes, Sphaeropsidales,
Leptostromataceae
Pycnidia dimidiate, having a radiate cover over
the top half only, on a dark subicle or mycelial
crust; pseudoparaphyses present; conidia hyaline,
one-celled.
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