Biology Reference
In-Depth Information
unimportant as a leaf spot; fruits have a hard,
dry rot.
Phyllosticta wistariae
Wisteria Leaf Spot
, more
important in the South.
Pirostoma nyssae (see
Tubackia dryira
).
▶
Tupelo Leaf Spot
.
Tubackia dryina (formerly
Pirostoma nyssae
).
Tupelo Leaf Spot
.
Physoderma
Placosphaeria
Chytridiomycetes, Blastocladiales
Deuteromycetes, Coelomycetes
Definite mycelium with terminal and intercalary
enlargements which are transformed wholly or in
part into sporangia and resting spores; sporangia
rare, oospores abundant, globose or ellipsoidal.
Affected plant parts are discolored or slightly
thickened.
Physoderma maydis
Brown Spot
of corn,
Corn
Measles
,
Corn Pox
,
Dropsy
, most prevalent in
the South. Very small, bleached or yellowish
spots darken to brown or reddish brown with
a light margin. Adjacent spots may coalesce
to give the whole blade a rusty appearance.
Spots on midrib and leaf sheath are larger, up to
1/4 inch, irregular to square, darker than leaf
lesions. The entire sheath may turn brown on
death of host cells; the epidermis ruptures, expos-
ing brown spore dust. In severe infections low
nodes are girdled so stalks break over. The resting
spores remain in soil or plant refuse over winter,
germinating by swarm spores the next spring.
A fairly high temperature and low, wet land
favor the disease. Remove plant refuse early;
rotate crops.
Pycnidia globose, dark, in a discoid stroma;
spores hyaline, one-celled; teleomorph state in
Dothideales
.
Cheilaria agrostis (formerly
Placosphaeria
graminis
).
Tar Spot
on redtop grass.
Placosphaeria
graminis (see
Cheilaria
▶
agrostis
).
Tar Spot
on redtop grass.
Placosphaeria haydeni
Black Spot
,
Tar Spot
on
goldenrod and aster, stems and leaves.
Laestadia (Plagiostoma)
Ascomycetes, Diaporthales
Spores two-celled, hyaline.
Laestadia asarifolia (formerly
Plagiostoma
asarifolia
).
Fruit Rot
,
Early Rot
,
Scald
,
Blast
on
cranberry, also blueberry. Small, circular gray
spots, with one to six pycnidia in center, have
brown margins. The disease is unimportant as
a leaf spot; fruits have a hard, dry rot.).
Leaf
Spot
on wild ginger.
Mycosphaerella
prenanthis (formerly
Plagiostoma
prenanthis
).
Leaf
Spot
on
Phytophthora
prenanthis.
Plagiostoma
Laestadia
asarifolia
).
Fruit Rot
,
Early Rot
,
Scald
,
Blast
on
cranberry, also blueberry.
Plagiostoma prenanthis (see
Mycosphaerella prenanthis
).
Leaf Spot
on
prenanthis.
asarifolia
(see
▶
Phytophthora ramorum
Leaf Spot
(sudden
oak death), California buckeye.
Tubackia (Pirostoma)
Deuteromycetes, Coelomycetes
Pleiochaeta
Pycnidia superficial, with a shield; spores one-
celled, dark.
Pleiochaeta setosa
Leaf Spot
on Genista.
