Biology Reference
In-Depth Information
a green zone that keeps its color even if the rest of
the leaf turns yellow. Small black pycnidia are
deeply embedded in the dead tissue, often in
concentric rings. In moist weather conidia ooze
from pycnidia in pink tendrils. The fungus win-
ters in old plant refuse, and ascospores are forc-
ibly ejected from perithecia in spring. The disease
is confined to the Pacific Coast and, as black
blight, is serious on the seed crop in the Puget
Sound area. Sanitary measures and crop rotation
keep it in check.
Mycosphaerella caroliniana
Leaf Spot
,
Purple
Blotch
on oxydendron (sourwood). Reddish or
purple spots on foliage in midsummer have dry,
brown centers. Pycnidia embedded in tissue
break through lower surface, spores being formed
in great numbers.
Mycosphaerella caryigena
Pecan Downy
Spot
. Conidial stage has been listed as a
Pseudocercosporella caryigena
. Leaf spots are
pale yellow when young, turning yellow-brown,
brown, or black. Conidia produced in minute
acervuli on underside of leaves form a white
downy or frosty coating; leaves may drop early.
Spores are spread in rain, fog, and dew. The fungus
overwinters in leaves, liberating ascospores in
spring to infect new foliage. Moneymaker and
Stuart varieties are especially susceptible.
Control
Turn under old leaves before spring
(plowing under winter cover in spring takes care
of this). Spray as for scab, bordeaux mixture
when leaves are half-grown and bordeaux plus
4 pounds of zinc sulfate when tips of small nuts
have turned brown.
Mycosphaerella
Mycosphaerella
colorata
Mountain-Laurel
Leaf Spot
.
Phyllosticta kalmicola
.
Mycosphaerella (Anamorph,
Pseudocercospora
cruenta
) cruenta
Leaf Spot
,
Leaf Blotch
of
soybean, and kidney bean. Leaf spots distinct to
indistinct, circular to irregular, greenish to
yellowish to rusty brown to almost red, some-
times with gray centers.
Mycosphaerella effigurata (Anamorph,
Piggotia
fraxini
).
Ash Leaf Spot
, general east of the Plains.
Spots small, purple to brown with yellow borders.
Mycosphaerella fragariae
Strawberry Leaf
Spot
,
Black-Seed Disease
, general on straw-
berries. Leaf spots are first purple then reddish
with light brown or white centers, 1/8 to 1/4 inch
across. Spots are also present on petioles and fruit
stems, and occasionally there are black spots on
fruit, with blackened achenes prominent against
the white of unripe berries. Fruit is poor; total
yield is reduced; runner plants are weakened.
Conidia of the
Ramularia
stage are produced in
clusters of short conidiophores on underside of
diseased areas; perithecia are formed in autumn
at the edge of the leaf spots where the fungus
winters. New conidia are produced in spring
with most infection taking place through stomata.
There is a difference in varietal susceptibility.
Control
Set healthy plants in well-drained soil;
remove diseased leaves before planting; spray
with bordeaux mixture before planting and fol-
low with two or three more applications. The
conidia are very sensitive to copper, which pre-
vents sporulation and kills nongerminated spores.
Mycosphaerella fraxinicola (Anamorph,
Phyllosticta viridis
).
Ash Leaf Spot
, east of the
Rocky Mountains.
Mycosphaerella juglandis
Leaf Spot
of black
walnut.
Mycosphaerella liriodendri (
Phyllosticta
liriodendrica
).
Tulip-Tree Leaf Spot
.
Mycosphaerella louisianae
Purple Leaf Spot
of strawberry,
▶
cerasella
▶
Cercospora
circumscissa
.
Mycosphaerella (Anamorph,
Cercospora
)
cercidicola
Redbud Leaf Spot
, general. Spots
are circular to angular or irregular with raised
dark brown borders. With age, lesions become
grayish above and rusty brown on the undersur-
face, with the leaf tissue yellow-green outside the
borders. Spores are formed on fascicles of conid-
iophores projecting through stomata. The fungus
winters on fallen leaves, producing perithecia in
spring. Twigs may be attacked as well as foliage.
Mycosphaerella citri
Leaf Spot or Greasy Spot
on citrus.
in the South. Large,
irregular,
reddish purple areas.
Mycosphaerella mori
Mulberry Leaf Spot
,
widespread, with the conidial stage reported
variously as
Cercosporella, Cylindrosporium,
Phloeospora, Septogloeum
, and
Septoria
. Yellow
areas on upper leaf surface are matched by
