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.

The filbert bud mite[17] is occasionally of economic importance as a
pest of filberts in Oregon and has been of some concern recently in New
York. It attacks the leaf and flower buds and catkins. Infested catkins
become distorted, rigid, and brittle, and yield no pollen. In Oregon
this pest has been controlled with 3 gallons of a dormant oil emulsion