Biology Reference
In-Depth Information
Control
is not easy. Spraying with lime sulfur
in March and October is fairly effective but may
be phytotoxic at high temperatures and low
humidity. Wettable sulfur has not been consis-
tently effective. Removal of witches' broom by
pruning back to normal lateral branches is effec-
tive only if the tree is slightly susceptible and
conditions for reinfection are unfavorable.
Heavy pruning stimulates new growth and
increases the amount of mildew. The Holm or
holly oak is apparently resistant to mildew and
well adapted to the coastal region.
Sphaerotheca
with fruit often failing to color. Resistant varie-
ties include Sparkle, Puget Beauty, Siletz and
India.
Sphaerotheca mors-uvae
American Goose-
berry Mildew
, also on currant; sometimes the
limiting factor in gooseberry production. Fruits
dry up with a brown, felty covering. Leaves and
canes are stunted with the usual white coating.
Perithecia are formed on canes, and ascospores
are discharged in early May as fruit is set. Conidia
for secondary infection are produced within 10
days. Spray with lime sulfur immediately after
bloom.
Sphaerotheca pannosa var. persicae
Peach
Mildew
, general on peach, also on almond, apri-
cot, nectarine, matrimony-vine, and
Photinia
.
The mycelium is pannose (ragged) or in dense
patches, persistent, usually satiny, shining white,
or sometimes grayish or brown. Immature fruits
are highly susceptible. They have brown blotches
and are scabby and malformed. The fungus win-
ters in shoots. Nonglandular varieties Peak and
Paloro are more affected than glandular Walton,
Johnson, Halford, and Stuart, at least in Califor-
nia. Sulfur in the spray schedule for brown rot
should control mildew without additional treat-
ments. Karathane is effective but very slightly
phytotoxic. Lime sulfur is recommended.
Sphaerotheca
castagnei
(see
Sphaerotheca
fuligena
). On buffaloberry, spirea.
Sphaerotheca fuliginea (formerly
Sphaerotheca
castagnei
). On buffaloberry, spirea.
Sphaerotheca fuliginea
Powdery Mildew
of
summer squash and cucurbits.
Sphaerotheca
fusca Powdery mildew;
on
ground-cherry.
Sphaerotheca lanestris (see
Cystotheca
lanestris
).
Powdery Mildew
of coast live oak on
Quercus agrifolia
in California, reported also on
white, southern red, bur and post oaks.
Sphaerotheca macularis (
S. humuli
).
Hop Mil-
dew
, also on fruits, blackberry, dewberry, goose-
berry, raspberry, strawberry, rose (probably
rarely in this country), and other ornamentals,
including
Agastache
, betony, buffaloberry, del-
phinium,
Epilobium, Erigeron
, gaillardia, gera-
nium, geum, gilia, hawksbeard, hawkweed,
Hydrophyllum
, kalancho¨, matricaria, meadow-
sweet, ninebark,
Polemonium
, phlox, sumac, spi-
rea, tamarisk and
Vernonia
.
This mildew may be important on Latham
variety of raspberry, appearing on new canes
when they are 2 to 3 feet high. The tip leaves
are dwarfed, mottled, and distorted, almost as if
they had mosaic. The undersurface of leaves is
water-soaked or has the familiar white coating.
There is no specific control except to space plants
for free air circulation.
The powdery mildew sometimes serious on
strawberries in northeastern and Pacific Coast
States is probably a special strain. The edges of
affected leaves curl upward, exposing the lower
surface, where the powdery frosty growth is evi-
dent. Fruit, stems, and berries may be affected,
pannosa
var.
rosae
(
Podosphaera pannosa
).
Rose Mildew
, general
on rose; distinct from peach mildew but appar-
ently not confined to rose, since apricots growing
near roses have been infected.
Sphaerotheca phytoptophila Associated with
gall mites causing witches' broom on hackberry.
The mycelium is evanescent; perithecia are
formed inside loose scales of enlarged buds.
Sphaerotheca sp. On
Tolmiea
, pick-a-back
plant, in greenhouse.
▶
Uncinula
Perithecia globose; appendages uncinate, slightly
coiled at tips; several asci, with two to eight
spores.
Pleochaeta
prosopidis (formerly
Uncinula
prosopidis
).
