Types of Garden Enemies
Control. Parathion or DDT aerosols are used indoors; DDT sprays in gardens.

ONION THRIPS (Thrips tabaci).
This species is found on nearly all garden plants; it is injurious to rose and other ornamentals as well as to onions and various vegetables. Whitish blotches appear on onion leaves; tips wither and turn brown; the entire plant may be distorted and blasted and fall over; bulbs are undersized. Rose blooms are distorted, petals spotted and streaked. Nymphs and adults are both yellow, the former somewhat paler. There are 5 or 6 generations a year.

Control. Dust onions with 5 or 10% DDT dust or spray with 4 table- spoons 50% wettable powder to a gallon of water. Use lindane, or per- haps chlordane, on ornamentals.

PRIVET THRIPS (Dendrothrips ornatus).
In certain seasons this eastern species turns privet hedges uniformly gray; they look as if covered with dust. On close examination you can see the dark insects, with a bright band, on both leaf surfaces. Because they are not hidden, they are relatively easy to kill widi nicotine soap, rotenone, or any good contact insecticide. DDT is effective but also increases mite injury.

TREEHOPPERS
Treehoppers are very queer-looking relatives of leafhoppers, in the order Homoptera. Their thorax, technically a pronotum, is enlarged into grotesque forms. The BUFFALO TREEHOPPER (Ceresa bubalus) does somewhat resemble a buffalo in side view, is wedge-shaped viewed from above. It is green, blunt at the head end, about !4 inch long, and the female has a sharp ovipositor. Plant injury comes not so much from sucking as from the crescent-shaped slits, like parenthesis marks, made in egg-laying. Fruit trees are weakened and have a scaly appearance. My personal interest in this treehopper comes from its habit of spreading spores of the brand canker fungus when it makes its egg slits in rose canes. Oil sprays sometimes kill overwintering eggs. The TWO-MARKED TREEHOPPEE (Enchenopa btnotata) is found on butternut, locust, sycamore, redbud, and other trees. It is brown with two yellow spots and looks like a bird in sideview. The female covers her eggs on the bark with white frothy material in corrugated layers. Such white masses are sometimes mistaken for cottony maple scale. See Figure 56B, C.

VIRUS DISEASES
The word virus means poison or venom. Virus diseases, whether of plants or man and animals, are caused by a poison or infective principle so small it passes through the finest filter. Under a powerful electron microscope it is revealed as a particle or body which is apparently a protein molecule and on the borderline between living and non-living matter




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