PEACH LEAF CURL (Taphrina deformans).
This is an old disease, known
for more than a century in all peach districts. Young leaves are
arched and reddened, then curled and puckered, greatly increased in
thickness. They sometimes look as if a gathering string had been run
along the midrib and pulled tight. Trees may loose most of their leaves,
with resulting failure to set fruit and winter injury. Young fruit is dis-
torted or cracked. A silvery sheen over infected surfaces is a spore-bearing
layer, and spores are discharged from this to the bark of twigs and bud
scales. There they bud into yeastlike spores which remain alive over
winter and are washed by spring rains to opening leaf buds.
Control. Apply a dormant spray late in autumn or before buds swell in
the spring. Lime-sulfur at a 1 to 15 dilution is effective; bordeaux mix-
ture (10-10-100) is recommended in California and other warm climates.
Leafhoppers are sucking insects in the order Homoptera. Adults have
2 pairs of membranous wings, held in a rooflike position when at rest,
thus differing from true bugs which fold their wings flat over the abdomen. Leafhoppers have wedge-shaped bodies, jump quickly when disturbed, feed from the underside of foliage, and by their sucking produce a pattern of white dots on the upper leaf surface (Figure 31). If
these stippled dots are numerous, there is general loss of color in the
leaves. Sometimes the upper surface resembles stippling by lace bugs,
but the undersurface never has the brown varnished effect. Sometimes you
can find there white cast-off skins where the nymphs have molted. Some
leafhoppers introduce a toxin into plants causing browning and curling
of leaf margins; many are vectors of plant disease-aster yellows, elm
phloem necrosis, Pierce's disease of grapes, curly top, peach yellows,
peach X-disease, and phony peach. Almost all garden plants can be
troubled by leafhoppers, but they are a special nuisance on roses and
dahlias, and on Virginia creeper late in the season.
BEET LEAFHOPPER (Circulifer tenellus).
This is a western insect, yellowish
or pale green, of importance because it transmits the curly top
virus to many ornamentals as well as beets and tomatoes. It winters on
Russian thistle and other weeds, and the control program should include weed removal as well as spraying or dusting with DDT.
GRAPE LEAFHOPPER (Erythroneura comes).
This pale yellow leafhopper
with red markings is almost universally present on grape and
Virginia creeper in late summer, sometimes on apple and other plants.
Foliage is greenish yellow, vines are sickly, and the grape harvest is
reduced in both quality and quantity