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 or 6-1/2 to 8 gallons of liquid lime-sulfur in water to make 100 gallons of spray just as the buds are opening. Related species of similar habits that attack walnuts have been controlled with 9 or 10 gallons of liquid lime-sulfur in water to make 100 gallons of spray applied at the time the buds break or soon thereafter.
The feeding of the spider mites on the foliage of infested trees causes it first to have a bronzed or scorched appearance, and later to dry up and fall. These mites frequently become abundant following the use of some of the new organic insecticides, such as DDT and BHC, which destroy their natural enemies and perhaps have other effects on the trees favorable to mite activity. The European red mite, which overwinters on the trees in the egg stage, can be controlled by application of 3-percent oil-emulsion spray in the late-dormant period. The two-spotted spider mite and related species, as well as the European red mite if it is not controlled with the dormant spray, can be controlled with a spray containing 1 pound of a 15-percent parathion or 1-1/2 pounds of a 15-percent Aramite wettable powder per 100 gallons. Apply the spray before many leaves show the typical bronzing or leaf scorching. If the infestation is heavy, a second application may be necessary in about 8 or 10 days. Be sure to follow the precautions on the container, especially if you use parathion.
PRESIDENT MacDANIELS: We greatly appreciate your care in getting this thing together, and we know it is going to be a great help to us when we get it printed as a matter of reference.
MR. O'ROURKE: I'd like to ask Dr. Baker if insects are getting stronger or if the chemicals are getting weaker. I refer to the rates of application. Formerly we were told that one-half pound of parathion for one hundred gallons and one pound of DDT would control almost all insects. I note the rates are going up.
MR. BAKER: That's true, particularly with parathion. The first year that we tested parathion on any scale we thought a quarter to a half a pound would control mites for 30 days or more and would control curculio for 20 or 30 days, but the next year we used it we found that was a little optimistic. It seems that each year since we have had to use more of it or use it more often, or with mites, particularly, there are a number of instances where it just doesn't control them at all.
Two years ago that came to notice in the Wenatchee area of Washington on apples. Mites in a certain orchard just couldn't be controlled with parathion. A year ago the area in the Pacific Northwest where that was true was extended and included several orchards of the Yakima Valley. This year it also includes orchards in the East, in New York. We have seen an orchard where two pounds of parathion and a hundred gallons of water just didn't have much effect on the mites, and we have had to use other materials. We hear of instances of codling moth on apples where DDT doesn't seem to be as good as it was in the beginning. I have talked with some of the people working on the problem, and they find that there is quite a difference between different brands of some of these insecticides. Possibly that is the answer.