and varieties. Many of these trees are grown for
ornamental, shade, or timber purposes rather than for nut production.
Owing to these conditions and to a series of spring frosts since 1945,
it has been impossible to conduct insecticide experiments on an adequate
basis of replicated plats.

Although much is to be learned regarding time of application of the
sprays and the proper dosage, the use of DDT can be recommended as a
standard practice, because it has proved highly valuable in protecting
chestnut trees from heavy losses due to the chestnut weevil. It is the
purpose of this paper to discuss some of the experiments that have been
made with DDT and the observations made on the time of egg deposition.

+Nature and Extent of Injury+

The worms attacking chestnuts are the larvae of two very similar species
of weevils, one larger than the other. The adults are medium-sized
beetles having extremely long, slender beaks. With these they drill
through the husk of the nuts, making openings through which they insert
their eggs into the nuts. From these eggs the familiar worms develop.
Weevil injury varies greatly in different chestnut-growing localities.
It is not unusual for 50 to 75 percent of the nuts to be wormy, and
often infestation reaches 90 to 100 per cent. The small weevil does the
most damage, but there are indications that this may not always be true.
Because the mouth parts of the adult are situated at the end of an
extremely long and slender beak, it can obtain most of its food from
beneath the surface of the host plant. For this reason, stomach poisons
applied to trees have not been eaten by these weevils, and hence have
been of no practical value. As DDT kills by contact, it is necessary
only for the body of the insect to come in contact with DDT.

+Life Histories of the Weevils+

In the vicinity of Beltsville, Md., the adults of the large chestnut
weevil[8] leave the soil about August 15. The date will vary, of course,
with season and locality. Both males and females soon begin to feed by
piercing the burs with their long beaks. Mating begins soon after the
weevils collect on the trees, and egg laying follows shortly. The eggs
hatch within a few days and the worms develop within the nut. A few of
the worms will complete their growth and leave before the nuts fall, but
most of them emerge from the nuts after they have fallen. The worms then
enter the soil, where they build cells and remain until they c