Part 22 (1/2)

[Ill.u.s.tration: Fig. 7.--Injury to young pecan tree by the fall webworm.]

[Ill.u.s.tration: Fig. 8.--Larvae of the walnut caterpillar.]

[Ill.u.s.tration: Fig. 9.--Caterpillar of the hickory tussock moth.]

[Ill.u.s.tration: Fig. 10.--Rose chafer beetles on chestnut blossoms.]

Insects Attacking the Foliage

~Black pecan aphid.~ Pecan trees at times suffer sufficient damage from the black pecan aphid[15] to cause considerable defoliation (Fig. 5) during the latter part of the season. The injury to foliage in its earlier stages consists of irregularly shaped yellowish areas which turn brown when the tissues die.

[15] ~Melanocallis caryaefoliae~ (Davis).

This aphid is usually controlled with nicotine sulfate (40 percent nicotine), 3/8 pint plus summer oil emulsion, 2 quarts per 100 gallons of spray. Parathion and benzene hexachloride have given good results in experimental work but are not yet generally recommended.

~Pecan phylloxera.~ The pecan phylloxera[16] is related to aphids. It attacks princ.i.p.ally the vegetative parts of the tree such as the leaves, petioles, and shoots on which galls (Fig. 6) are produced. Pecans, hickories, and other species of nuts are subject to infestation.

[16] ~Phylloxera devastatrix~ Perg.

In the past a spray of nicotine sulfate (40 percent nicotine) 13 ounces combined with either lime-sulfur solution, 2-1/2 gallons per 100 gallons of water, or lubricating-oil emulsion, 2 quarts per 100 gallons, applied in the late dormant period has been the standard recommendation. In recent experiments in the South with some of the new organic sprays, benzene hexachloride and some of the dinitro compounds have indicated good promise.

~Fall webworm,~[17] ~walnut caterpillar,~[18] ~and hickory tussock moth.~[19] The caterpillars of these species (Figs. 7, 8, 9) are frequent pests on the foliage of nut trees. They often defoliate entire branches.

[17] ~Hyphantria cunea~ (Drury).

[18] ~Datana integerrima~ (G. and R.)

[19] ~Halisidota caryae~ (Harr.)

The best time to apply control measures is as soon as possible after the caterpillars hatch. The insects can be readily destroyed with lead a.r.s.enate, 3 pounds, or DDT (2 pounds) of 50 percent wettable powder, per 100 gallons, applied when they appear. Other new organic insecticides may also be effective but have not been widely tested.

~The rose chafer and j.a.panese beetle.~ Adults of the rose chafer[20] (Fig.

10) and the j.a.panese beetle[21] are voracious feeders on the foliage of nut trees and must be destroyed if severe injury is to be avoided.

[20] ~Marcordactylus subspinosus~ (F.).

[21] ~Popillia j.a.ponica~ Newm.

Fortunately these insects may now be controlled by spraying with DDT, 2 pounds of 50-percent wettable powder per 100 gallons of water, when the beetles appear. In the case of the j.a.panese beetle a second application may be necessary if the infestation is heavy.

~Spider mites.~ Nut trees, especially those which have been sprayed with DDT, may become seriously injured by various species of mites.[22] DDT is very toxic to the natural insect enemies of plant-feeding mites and therefore the mites build up to injurious numbers.

[22] ~Tetranychus~ sp. and others.

Of the various miticides recently tested on pecan, a spray of parathion was the most promising. In some recent tests for the control of spider mites on chestnut trees, 1-1/2 pounds of 15 percent parathion wettable powder per 100 gallons of water was effective. Do not use parathion unless you observe all the precautions contained on the package label of the material.

[Ill.u.s.tration: Fig. 11.--Larva of the twig girdler. Enlarged.]

[Ill.u.s.tration: Fig. 12.--Adult of the flatheaded apple tree borer.