s more resistant to it. The occurrence of
injury to the foliage and fruit of some varieties of apples when this
insecticide is used is under investigation.

Benzene hexachloride (10 percent gamma isomer, wettable) is being used
at 2 to 4 pounds, and sometimes less depending upon the insect, per 100
gallons of water. Wettable mixtures containing 25 percent of lindane
(approximately pure gamma isomer) are used at dosages which would give
an equivalent quantity of the gamma isomer in the diluted spray.

Chlordane is usually employed at the rate of 2 to 3 pounds of 50 percent
wettable powder and toxaphene at 2 to 4 pounds of 40 percent wettable
powder per 100 gallons.

These insecticides are also being sold for use as dusts, either ready to
use or in a more concentrated form which can be reduced to dusting
strength through the addition of inert material.

~Spray Residues.~ Spray residues are not important on nut crops, but on
fruits it is important to time the insecticide applications so that
harmful residues are avoided. Animals should not be allowed to graze
vegetation beneath trees recently treated. Instructions on the packaged
insecticide should be followed.

~Effect on beneficial insects.~ Since the more potent of the newer organic
insecticides are toxic to many parasitic and predatory insects, all of
which help to reduce the populations of injurious species, these
insecticides, if used, must be largely relied upon to effect control by
themselves. Often no immediate assistance is forthcoming from beneficial
insects after these materials have been used.

Nut Insect Investigations

Except for studies on the chestnut weevils, nut insect investigations by
the Bureau of Entomology and Plant Quarantine are being conducted
primarily on the pecan at southern laboratories. Many of the remarks in
this paper are therefore based on information obtained from these
laboratories. In view of the short time the new organic insecticides
have been available, work to determine their place in nut insect control
programs is largely in the experimental stage. Much further work will be
necessary before detailed instructions can be given for their general
use.

Insects Attacking the Nuts

~The Pecan weevil.~ The adult of the pecan weevil[8] is a snout beetle
that attacks not only pecan throughout the South but also hickory in the
eastern half of the United States. During mid-season, previous to the
formation of the kernel, nuts