There are 2 generations, but the
fall brood accounts for general loss of color in Virginia creeper and
Boston ivy. Use DDT on ornamentals and as a pre-blossom spray on
grapes, but change to DDD for grapes near harvest.
POTATO LEAFHOPPER (Empoasca fabae).
This is often considered the most
injurious potato pest in the eastern half of the United States, and
it causes serious hopperburn and stunt of dahlias. The adult is green,
wedge-shaped, 1/8 inch long. Each spring it migrates up from the South
where it has been wintering on legumes and weeds. The leafhoppers
appear first on northern beans, then swarm over to potatoes, laying eggs
in leaf veins or petioles. The small, pale nymphs, similar to adults except for lack of wings, hatch in about 2 weeks and go through 5 molts to
the adult form, often leaving their shed skins on the back of leaves.
On both potato and dahlia the tips and margins of leaves turn brown
and curl under; dahlias may be greatly stunted. African marigolds sometimes show curling and reddening of leaflets and either a stunting or
wilting of young tips. I have not seen it recorded in literature, but I
think that the triangular browning I find so often at the tips of rose
leaves in August is also due to this leafhopper.
Control. DDT has proved to be very effective in leafhopper control.
In fact, no one realized how much the potato yield was reduced by
leafhopper injury before DDT was available. For ornamentals use a
3 or 5% DDT dust or 1 tablespoon 50% wettable powder per gallon
ROSE AND APPLE LEAFHOPPERS.
At least 3 species, the rose leafhopper
(Typhlocyba rosae), white apple leafhopper (T. pomaria), and the
common apple leafhopper (Empoasca maligna) cause conspicuous damage to rose and apple foliage, the fall broods being worse, and roses in the
vicinity of apple trees being sucked white even into December. They
winter as eggs on apple bark or rose canes, first-generation nymphs appearing when leaves are full grown. They conspicuously injure even
the shiny foliage of Dr. Van Fleet and similar climbers considered rather
pestproof. The adults are pale yellow or greenish white. They may slightly
curl leaves by their sucking but do not cause brown margins like potato
leafhoppers. They can, however, take practically all the color out of rose
leaves, more often in the fall when gardeners have ceased spraying for
the season than in spring.
Control. DDT is most effective, but since this so greatly increases the
red spider problem on roses I use it only for the late summer brood, adding it to my regular three-in-one spray after mites are no longer a
problem. Rotenone and pyrethrum or nicotine sulfate and soap sprays
give fair control of the spring brood if they are started early enough
and repeated weekly.