Biology Reference
In-Depth Information
whitish patches underneath, the fungus forming
a white downy or powdery coating. The disease is
most serious in shady locations.
Mycosphaerella nigromaculans
Black Stem
Spot
of cranberry, reported from all cranberry
areas, often associated with red leaf spot. The
fungus enters through leaves, grows down the
petioles, and forms elongated black spots on the
stems, which may be completely girdled, followed
by defoliation. Fruiting bodies are produced in
autumn on dead stems with ascospores discharged
in rainy periods in spring. The anamorph state of
the fungus is a
Ramularia nigromaculans
.
Mycosphaerella nyssicola (Anamorph,
Phyllosticta nyssae
).
Tupelo Leaf Spot
,onsour
gum and water tupelo. Purplish irregular blotches,
an inch or more across, are scattered on upper leaf
surface with lower surface dark brown. There may
be heavy defoliation. Perithecia mature in spring
on fallen leaves.
Mycosphaerella personata (Anamorph,
Isariopsis clavispora
).
Leaf Spot
, widespread on
muscadine and other grapes after midseason.
Spots are dark brown, 1/4 to 1/2 inch, surrounded
by a yellow circle but with a narrow band of
normal green between spot and circle.
Mycosphaerella populicola (Anamorph,
Septoria populicola
); M. populorum
(
S. musiva
).
Leaf Spot
of native poplar;
Canker
on twigs and branches of hybrid poplars.
Mycosphaerella psilospora (Anamorph,
Septoria querceti
).
Oak Leaf Spot
on red and
other oaks, common in Iowa. Spots very small,
circular, with strawcolor centers and dark margins.
Mycosphaerella ribis
Leaf Spot
of flowering
currant.
Mycosphaerella ribis (
M. grossulariae
,
Anamorph,
Septoria ribis
).
Leaf Spot
of goose-
berry, current. Numerous small brown spots with
grayish centers are formed on both sides of
leaves; there may be premature defoliation. The
fungus winters in leaves, producing ascospores in
late spring. Two sprays of bordeaux mixture plus
1 pint of self-emulsifying cottonseed oil per 100
gallons have given good control of leaf spot on
gooseberries in New York. The first application
is about June 1, the second in July right after fruit
is picked.
Mycosphaerella
rosicola
▶
Cercospora
rosicola
.
Mycosphaerella rubi
▶
Septoria rubi
.
Mycosphaerella pyri (Anamorph,
Septoria
pyricola
).
Pear Leaf Spot
, also on quince, occa-
sional on apple. Spots are small, 1/8 to 1/4 inch,
grayish in center, dotted with black fruiting bod-
ies, with a well-defined dark brown margin.
There are marked differences in susceptibility in
pear varieties. Flemish Beauty, Duchess, and
Winter Nellis are moderately, and Kieffer very,
resistant. Sprays applied for leaf blight or scab
control leaf spot.
Mycocentrospora
Mycocentrospora verrucosa
Leaf Spot
on
euonymus.
Myrothecium
Deuteromycetes, Hyphomycetes
Sporodochia cushionlike, light or dark; conidio-
phores subhyaline to colored, repeatedly
branched, bearing conidia terminally; conidia
subhyaline to dark, one-celled, ovoid to elongate;
weakly parasitic or saprophytic.
Myrothecium roridum
Leaf Spot
on snap-
dragon, stock, eremurus, gardenia, hollyhock,
aeschynanthus, aglaonema, aphelandra, dieffen-
bachia, episcia, fittonia, nematanthus, hoya,
peperomia, pilea, and sphathiphyllum. Tissues
are dry, brittle, with black sporodochia. Snap-
dragon leaves and flowering stems wilt, with
sunken cracked cankers. Avoid excessive mois-
ture; sterilize soil.
Nematostoma
Ascomycetes, Dothideales
Nematostoma occidentalis
Leaf Hair Discolor-
ation
on Artemisa.
