it has not been
possible for the Bureau of Entomology and Plant Quarantine to give
attention to many of the pests of northern nuts. A great deal of work
has been done on the pests of pecans in the South, and some work on
those that attack filberts and chestnuts. In addition, some of the pests
with which you are concerned, or others similar to them, are receiving
attention in connection with studies of pests of tree fruits. The
results of these studies will give you up-to-date information applicable
to your particular problems.

The timely use of insecticides is the most effective means of combating
most injurious insects, but if spraying is not possible, other methods
can often be used to prevent or reduce damage. A great many new
insecticides have become available during the last six or seven years.
Work with them has resulted in the development of treatments effective
against a number of pests for which there was formerly no known means of
control and markedly more effective treatments for the control of
others. It is my purpose to bring to you as much of this new information
as is applicable to your problems.

Leaf-feeding Caterpillars

The fall webworm[3] and the walnut caterpillar[4] are the leaf-feeding
caterpillars most commonly reported as attacking northern tree nuts.

Fall webworms[5] are the insects usually responsible for unsightly webs
on or near the end of the branches of the trees during the summer and
fall. They enlarge the webs as they need more leaves. When nearly full
grown they scatter to complete their feeding. The full-grown
caterpillars are a little more than an inch in length and are covered
with long black and white hairs. They spend the winter in cocoons in
trash on the ground or just below the surface of the soil. There are two
broods a year in many areas, the second usually being the more numerous.

Control can be obtained by applying a spray containing 3 pounds of lead
arsenate with an equal quantity of hydrated lime (to prevent possible
injury to the foliage), 2 pounds of 50-percent DDT wettable powder, or 2
pounds of 15-percent parathion wettable powder per 100 gallons of water.
Apply the spray when the caterpillars are still small. Follow the
precautions furnished with each package. Parathion is a particularly
dangerous material to use. If you are not equipped to spray or have only
a few trees, you can control this insect by removing the webs from the
trees with a long-handled pru