Biology Reference
In-Depth Information
Phyllosticta solitaria
Apple Blotch
, wide-
spread on apple and crabapple in eastern states,
serious in the South and in the Ozark section of
Missouri, Arkansas, Oklahoma, and Texas. The
disease is also called fruit blotch, dryrot, black
scab, late scab, cancer, and tar blotch. From Kan-
sas eastward it is second in importance to apple
scab. Leaf spots are very small, round, white,
with a single black pycnidium in the center of
each. Larger elongate lesions are formed on
veins, midribs, and petioles. Leaves do not turn
yellow, but they drop prematurely if spots are
numerous. Cankers on twigs and branches are
located at leaf nodes or base of spurs. The first
season they are small, purple to olive in color; the
next season this portion is tan and the new area
dark purple, often slightly raised. Pycnidia
formed in twig lesions wash to leaves, fruit, and
new shoots, discharged only after heavy rains and
in warm weather. Heavily fertilized trees are
more susceptible.
Fruit blotches are brown, irregular, feathery at
the margin, studded with numerous pycnidia.
They afford entrance to secondary decay organ-
isms and may develop deep cracks, but the blotch
fungus itself is superficial. It winters in infected
twigs and bark cankers.
Control
Secure healthy nursery stock. Some
varieties, including Grimes Golden, Jonathan,
Stayman Winesap, and Winesap, are rather
resistant.
Mycosphaerella
Blights
.
Mycosphaerella dendroides (
Cercospora
halstedii
, Anamorph).
Pecan Leaf Blotch
,on
pecan in the South, on hickory in East and
South, a foliage disease of nursery and orchard
trees. Olive green velvety tufts of conidio-
phores and spores appear on undersurface of
mature leaves in June andJuly(inFlorida),
and yellow spots appear in corresponding
areas on upper leaf surfaces. Black pimplelike
perithecia are produced in the tufts about mid-
summer, united in groups to give the leaf
a shiny black, blotched appearance after the
spores are washed away. In nursery trees, defo-
liation, starting with basal leaves and
progressing upward, may be serious. The dis-
ease is of little consequence to orchard trees
unless they have been weakened by
overcrowding, borer attack, or other cause.
The fungus winters in fallen leaves. To control
clean up fallen leaves.
Mycosphaerella diospyri
Leaf Blotch
of Japa-
nese persimmon.
Mycosphaerella lythracearum (
Cercospora
punicae
, Anamorph).
Leaf Blotch
,
Fruit Spot
of
pomegranate. The anamorph state has been
thought the same as that on crape-myrtle
(
Cercospora lythracearum
), but is now consid-
ered distinct. Leaf spots are circular, small, dark
reddish brown to almost black, sometimes gray-
ish brown.
▶
Septoria
Blights
.
Septoria agropyrina
Brown Leaf Blotch
on
wheat grasses.
Septoria elymi
Speckled Leaf Blotch
on
wheat grasses. A salt and pepper effect with
numerous pycnidia in pale gray, tan, or fuscous
lesions.
Septoria macropoda
Purple Leaf Blotch
, gen-
eral on blue grasses. Irregular blotches on blades
are mottled greenish, then gray, tan or brown,
finally bleached nearly white. Pycnidia are
round, flattened, and light brown.
▶
Phoma
Blackleg
.
Phoma arachidicola
Web Blotch
of peanut.
▶
Phyllosticta
Blights
.
Phyllosticta congesta
Leaf Blotch
of garden
plum.
▶
