Types of Garden Enemies
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
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.

Fig. 31

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




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