Biology Reference
In-Depth Information
entrance. Small, sunken lesions give a flattened
appearance to some seedlings. Overhead irriga-
tion in a nursery is a predisposing factor, and
a large amount of stock can be blighted in
a very short time. Older trees in home
plantings suffer from twig blight. The fungus
winters on infected plant parts and remains viable
at least 2 years.
Control
Have seedbeds well drained; water by
ditch irrigation; remove and burn diseased seed-
lings early in the season; keep seedbeds away
from older cedar trees; do not use cedar branches
or needles for mulching. Spray with fixed
copper or bordeaux mixture plus a wetting
agent, starting when growth begins and repeating
to keep new foliage covered. Spiny Greek and
Hill junipers and Keteller red-cedars are some-
what resistant.
Phomopsis kalmiae
Mountain-Laurel Leaf
Blight
,
Blotch
. Circular, brown, often
zonate areas on leaves, frequently starting near
margin or tip, gradually enlarge and coalesce
until most of the blade is involved. The
fungus often works down the petiole to
cause a twig blight. The disease is more
prominent on bushes in the shade or under drip
of trees. Remove blighted leaves or clean up
fallen leaves.
Phomopsis longicolla
Black Pod Spot
and
Seed
on cowpea.
Phomopsis oblonga
Twig Blight
on Chinese
elm.
Phomopsis obscurans (formerly
Dendrophoma
obscurans
). Strawberry Leaf Blight, Angular
Leaf Spot. The lesions are large, circular to angu-
lar, reddish purple, zonate with age, having a dark
brown center, a light brown zone, and a purple
border. Spots may extend in a V-shaped area
from a large vein to edge of the leaf, with black
fruiting bodies appearing in the central portion.
Not serious before midsummer, the disease may
be destructive late in the season. The fungus
winters on old leaves.
Phomopsis occulta
Shoot Blight
of Colorado
blue spruce.
Phomopsis vexans
Phomopsis Blight
of egg-
plant.
Phyllosticta
Deuteromycetes, Coelomycetes
Pycnidia dark, with ostiole, in spots in leaves;
spores one-celled, hyaline. The characteristics
are the same as
Phoma
except that leaves rather
than stems are infected. Other species are listed
under Leaf Spots.
Phyllosticta batatas
Sweet Potato Leaf Blight
,
occasional from New Jersey to Florida, more
prevalent in the South but seldom important
enough for control measures. Numerous white
spots on leaves are bordered with narrow reddish
zones; pycnidia
are numerous;
spores
are
extruded in tendrils.
Phyllosticta
cryptomeriae
Needle
Blight
found on
Cryptomeria
.
Phyllosticta
lagerstroemiae
Tip Blight
of
crape-myrtle.
Phyllosticta multicorniculata
Needle Blight
of
fir.
Phyllosticta pteridis
Tip Blight
of fern. Leaves
lose green color; spots are ash gray with purple
brown margins and numerous black pycnidia in
center. A very weak bordeaux mixture has been
suggested for control; if overhead watering is
avoided, spraying may not be necessary.
Physalospora
Ascomycetes, Sphaeriales
Perithecia with papillate mouths, immerse in sub-
stratum but without well-defined stromata;
paraphyses present; spores one-celled, hyaline.
A few species cause blights; many cause rots.
Botryosphaeria obtusa (formerly
Physalospora obtusa
).
Cane Blight
of rose, also
Black Rot
of apple,
Canker
and
Dieback
of many
plants.
Rots
.
Glomerella cingulata (formerly
Physalospora
dracaenae
).
Dracaena Tip Blight
,
Leaf Spot
. Dis-
ease starts at the tips of lower leaves and spreads
down toward the base. Infected areas are sunken
and straw-colored, dotted with black specks of
Cankers and Diebacks
and also
▶
▶
Diaporthe vexans
.
Phomopsis vaccinii
Twig Blight
of blueberry.
▶
