f the chestnut crop at
Glenn Dale and 70 per cent at Elkton, and as a result only a few trees
suitable for tests were available. The remaining trees were not
sprayed. Four pounds of the standard mixture of equal parts of DDT and
kaolin were used to 100 gallons of water in all applications.

In Table 3 will be found information on the quantities of DDT used, the
schedules followed, and the results obtained during the period 1944
through 1947.

These results indicate clearly the effectiveness of DDT in chestnut
weevil control, in spite of numerous discrepancies brought about by the
small number and variability of the trees available for the tests. As
might be expected, programs of three applications were more effective
than those of only one or two. Of the single applications, those put on
during the latter half of August were much more effective than those
made during the first half of September, presumably because most of the
eggs had been laid by the early part of September.

These experiments gave fairly exact information on the relative
abundance of the two species of weevils. At Glenn Dale the small
chestnut weevil constituted 92 to 98 per cent of the population; at
Elkton, 61 per cent.

The matured nuts that fell from count trees were collected daily, and
one-third of each lot collected was used as a sample for determining the
percentage of wormy nuts. It was possible, therefore, to obtain a rough
estimate of the numbers of larvae produced on each tree. In 1946, from
1,863 nuts on a tree sprayed three times, 429 larvae emerged; and from a
comparable unsprayed tree having 2,610 nuts 16,494 larvae emerged. In
1947, 1,350 larvae were produced on 9 trees with an average crop of
1,361 nuts sprayed three times, compared with 14,505 larvae from 2,922
nuts on an unsprayed tree. These figures indicate that DDT sprays bring
about large decreases in the numbers of weevils and that the proper use
of DDT sprays on all host trees over a period of a few years would
doubtless reduce the infestation to a point where fewer applications
would be necessary for effective control of the chestnut weevils.

+Tentative Recommendations+

For the benefit of those who wish to try DDT for chestnut weevil
control, the following tentative recommendation is made:

Thoroughly apply +to all parts of the tree+ 2 pounds of DDT in 100 gallons
of water. For example, use 4 pounds of a wettable powder that contains
50 per cent of DDT, or 8 poun