Biology Reference
In-Depth Information
Pyricularia grisea
Leaf Blight
on creeping bent
grass and buffelgrass.
sclerotia made up of short, irregular, angular or
somewhat barrel-shaped cells.
Rhizoctonia ramicola
Silky Thread Blight
a southern disease similar to web blight caused
by
Pellicularia koleroga
. Perennial ornamental
hosts in Florida include elaeagnus, erythrina,
crape-myrtle, holly, guava, pittosporum, pyr-
acantha, Carolina jessamine, feijoa, and rhodo-
dendron. Tan spots with purple-brown margins
appear on leaf blades, dead lesions on petioles
and young twigs. When leaves are abscissed, they
are often held dangling and matted together by
brown fungus threads. Infection recurs annually
in moist weather with high daytime temperatures.
The fungus winters as mycelium in leaf lesions
and diseased twigs. Sclerotia are apparently
lacking in this species.
Rhizoctonia sp. (teleomorph,
Aquathana-
tephorus pendulus
).
Blight
on water hyacinth.
Rhizoctonia sp. (teleomorph,
Thanatephorus
cucumeris
).
Blight
on beet.
Needle blight
on
pine.
Rhizoctonia solani
Blight
of pistachio and
Cynodon
spp., and
Foliar Blight
of soybean.
Pythium
▶
Rots
.
Pythium myriotylum
Blight
of tomato.
Delphinella (Rehmiellopsis)
Ascomycetes, Dothideales
Perithecia single, globose, rupturing irregularly;
asci in fascicles, no paraphyses; spores hyaline,
two-celled.
Delphinella balsameae (formerly
Rehmiellopsis balsameae
).
Tip Blight
,
Needle
Blight
of balsam fir, on native balsam fir in north-
ern New England and on ornamental firs in south-
ern New England and New York. Infection is in
spring with needles of current season shriveled,
curled, and killed, often with a dieback of termi-
nal or lateral shoots and sometimes cankers at
base of infected needles. Satisfactory control on
ornamental firs has been obtained by three sprays,
at 10-day intervals, ofbordeaux mixture, the first
application made as new growth starts.
Rehmiellopsis balsameae (see
Rhizopus
▶
Rots
.
Rhizopus stolonifer
Seedling Blight
on lupine;
also caused by Pleiochaeta setosa, Alternaria sp.,
Aspergillus flavus, Aspergillus
Delphinella
balsameae
).
Tip Blight
,
Needle Blight
of balsam
fir, on native balsam fir in northern New England
and on ornamental firs in southern New England
and New York.
▶
niger,
and
Curvularia sp.
Rosellinia
Rhizoctonia
Ascomycetes, Xylariales
Deuteromycetes, Mycelia Sterilia
(Fungi Imperfecti)
Perithecia separate, superficial from the first, car-
bonaceous, not beaked, ostioles papillate; spores
dark, one-celled with a small groove.
Rosellinia herpotrichioides
Hemlock Needle
Blight
. Needle-bearing portions of twigs become
covered on underside with a grayish brown myce-
lial mat; black perithecia are produced in this mat
in great abundance. Ovoid, hyaline conidia are
formed on
Botrytis
-like conidiophores.
Sclerotial form of some species of
Pellicularia,
Corticium, Macrophomina
, and
Helicobasidium
.
Young mycelium colorless, with branches
constricted at points of origin from main axis,
but soon colored, a weft of brownish yellow to
brown strands, organized into dense groups,
