18 116 21 35 48 Oct. 1 108 31 44 69 +Spray Experiments in 1944+ Shortly after adults of the large chestnut weevil first appeared in the orchards in 1944, six trees isolated from other chestnuts were selected for treatment. Five trees were sprayed with from 1 to 5 pounds of technical DDT plus 1/2 pound of sodium lauryl sulfate to 100 gallons of water, and the sixth tree was left untreated as a check. A thorough application of a coarse, drenching spray at a pressure of 400 pounds per square inch was used in an attempt to force the DDT between the many spines of the burs. The DDT used was very coarse, and difficulty was experienced in getting a proper suspension. This formula was used, however, in preference to one which contained other ingredients that might have formed a protective coating over the particles of DDT. Heavy rains prevented later spray applications. Adult weevils obtained by jarring untreated trees were then confined in screen cages placed over the lower branches of the trees. At the end of each cage was a cloth sleeve which was tied to the limb to hold the cage in place. The treatments used and the results are given in Table 2. Table 2. Percentage mortality of chestnut weevils placed in field cages on trees at different intervals after they had been sprayed with with DDT, 1944. Strength of DDT (lb. per Small Chestnut Weevil Large Chestnut Weevil 100 gal.) 48 Hrs. 96 Hrs. 144 Hrs. 48 Hrs. 96 Hrs. 144 Hrs. 1 0 61 100 25 50 100 2 19 69 100 0 34 100 3 4 50 100 0 40 100 4 27 87 100 0 50 100 5 18 50 100 30 46 100 Check 0 0 0 0 7 7 Although the results obtained the first few days in the cages containing treated foliage were somewhat irregular, because of the small numbers of tests made, all weevils were killed within 6 days. The results indicate definitely that DDT is toxic to the adults of both species of weevils. No consistent differences between species were noted.