Biology Reference
In-Depth Information
summer black perithecia are formed in great
abundance. Powdery mildew on zinnias and chry-
santhemums usually starts so late in the season
that it is more conspicuous than harmful.
Control
Sulfur dust gives excellent control but is
phytotoxic to some melons and other cucurbits.
Sulfur-tolerant cantaloupes have been produced.
The variety Homegarden is supposedly resistant to
mildew and other pests. Keep phlox and other
ornamentals well spaced, and dust with sulfur at
the first sign of white growth. Because the perithe-
cia winter on old stems and leaves, plants should
be cut at ground level in autumn and burned.
Erysiphe cruciferarum
Powdery Mildew
on
cabbage and turnip.
Erysiphe graminis (syn. Blumeria graminis)
Powdery Mildew
of cereals and grasses, econom-
ically important on bromegrass, wheat, oats, bar-
ley, and rye; aesthetically important on lawn
grasses, wheatgrass, fescue, and bluegrass. The
foliage is yellow or chlorotic with a white weft or
mealy coating on upperside of leaf, which later
turns yellow and is often studded with tiny brown
perithecia. Seed from infected plants is small and
shriveled. Apply sulfur dust or wettable sulfur
sprays.
Erysiphe heraclei
Powdery Mildew
on carrot,
parsley, chervil (culinary herb), and celery.
Erysiphe orontii
Powdery Mildew
on mint.
Erysiphe panax
Powdery Mildew
on ginseng.
Erysiphe polygoni
Powdery Mildew
of
legumes, and many other vegetables and ornamen-
tals, about 200 species in 90 plant genera. Append-
ages are long or short, interwoven with the
mycelium, but the perithecia are not immersed in
it. Asci have three to six spores. Peas exhibit a white
powdery coating over leaves and pods, with
the latter often discolored. Leaves are sometimes
yellowish and deformed. The disease may be
severe on peas in arid sections of western states,
particularly on late homegarden varieties.
On beans, the mildew is grayish. It is prevalent
in California in cloudy weather or in autumn
when humidity is increased, but it is more impor-
tant in the Southeast. Other vegetables infected
by this species include lima bean, soybean, cab-
bage, turnip, radish, horse-radish, and carrot.
Spores germinate at quite low humidity.
The legume mildew is widespread on lupine,
occasional on sweet pea. Other ornamental hosts
include acacia, anemone, arrowleaf clover, can-
dytuft, calendula, California poppy, iceland
poppy, China aster, clematis, columbine, dahlia,
delphinium,
Erigeron
, gardenia, geranium,
hydrangea, honeysuckle, locust, matrimony-
vine, peony, sugar beet, and tulip-tree.
Teleomorph state found on sugar beet in CO,
MT, NB, WA, and WY.
Control
Choose resistant vegetable varieties or
dust with sulfur. Spray or dust ornamentals with
Karathane or sulfur.
Erysiphe taurica (
Leveillula taurica
). On
▶
leaves of mesquite.
Erysiphe trina (see
Brasiliomyces trina
).
Oak
Powdery Mildew
, on tanbark oak and coast live
oak, in California, causing witches' broom (but
▶
Sphaerotheca lanestris
for the common live-
oak mildew).
Erysiphe sp.
Powdery Mildew
on tomato.
Leveillula
Cleistothecia globose, or globose-depressed,
sometimes concave; asci two-to eight spored;
appendages floccose (cottony), simple or irregu-
larly branched; usually similar to mycelium and
interwoven with it.
Leveillula taurica (formerly
Erysiphe taurica
).
On leaves of mesquite. Commonly causes pow-
dery mildew on tomatoes in Eastern Mediterra-
nean region and reported on fresh market tomato
in California and Utah; also on cucumber, hibis-
cus, onion, guar, wild tobacco, cotton and desert
bird of paradise.
Microsphaera
Cleistothecia globose to globose-depressed;
appendages branched dichotomously at apex,
often ornate; asci several, with two to eight
spores.
Microsphaera penicillata Named for the alder
(
Alnus
), on which it is widespread, but best
known to gardeners as the
Lilac Mildew
. It also
