For many years these curculios have been controlled by spraying the trees soon after growth starts with lead arsenate, 2 pounds per 100 gallons, plus an equal amount of hydrated lime. One or two additional applications may be needed as new growth appears or as the nuts increase in size. Recent experimental work indicates that BHC or lindane may be more effective for controlling these insects. A spray containing 3 or 4 pounds of technical BHC (10-percent gamma) or 1-1/2 to 2 pounds of 25-percent lindane wettable powder per 100 gallons, applied when the buds show from 1/4 to 1 inch of green growth or when jarrings show adults are present, has given fairly good control. Walnut Husk Maggot The walnut husk maggot[15] attacks black and English walnuts, butternuts, and a few other nuts. The feeding of the larva, or maggot, in the husks impairs the quality of the kernels, discolors the shell, and often causes the shells to adhere to the nuts. It causes the most damage to English walnuts. This insect hibernates in the pupal stage in the ground. In midsummer it transforms to the adult fly stage, leaves the soil, and flies to the nut trees. After 1 to 3 weeks the flies lay eggs in the husks of the developing nuts. The eggs hatch in a week or 10 days, and the young maggots burrow within and throughout the husks of the nuts; they mature in the fall. The walnut husk maggot can be controlled by spraying the trees with lead arsenate or cryolite the latter part of July and again 3 to 4 weeks later. Use 2 or 3 pounds of lead arsenate plus an equal quantity of hydrated lime or 3 pounds of cryolite per 100 gallons of water. Filbert Moth The filbert moth,[16] a serious pest in some filbert orchards in Oregon, also causes some injury to chestnuts. Adult moths begin emerging toward the end of June and lay their eggs singly on the leaves beginning early in July. The newly hatched larvae tunnel through the husk and feed between the husk and the chestnut shell before entering the nut. This feeding produces a gummy substance, which causes the husk to adhere to the nut. The larvae may tunnel into the center of the kernel or excavate an irregular cavity in the side. They reach maturity about the time nuts are ripe, and then leave the nuts and construct cocoons in the soil in which to pass the winter. Control can be obtained by spraying the tree with lead arsenate or DDT early in July. Use 3 pounds of lead arsenate or 2 pounds of 50-percent DDT wettable powder in 100 gallons of water. Mites Two general types of mites sometimes damage nut trees, eriophyid mites and spider mites. The most important eriophyid mites are the wormlike gall mites and bud mites, most of which overwinter in the buds and cause deformities of the buds and leaves and otherwise limit their development. The spider mites may overwinter in the egg stage on the twigs or as adults in protected places on or beneath the trees. These mites feed primarily on the foliage.