Control. Parathion or DDT aerosols are used indoors; DDT sprays in
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 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.
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