34 MASS. EXPERIMENT STATION BULLETIN 428 



Tolerance tests of DN-111 and lead arsenate and wettable sulfur were made on 

 peaches, plums, and cherries. Two applications were made: the first, an equiva- 

 lent of late shuck spray, on May 29, and a later spray on July 13. No injury was 

 noted. 



Tolerance tests of both DN-111 and D-4 were made on 10 different types of 

 ornamentals during the period between May 31 and July 18. Considerable 

 foliage injury was observed on several plants following the May application. 

 Unmistakable burning, though less severe, resulted from early June application. 

 Injury was noticeably less following late June application, and very little or no 

 injury resulted, even on susceptible varieties, following July applications. 



The scarcity of apple leafhoppers in both early and late season throughout the 

 State made it impossible to run the tests planned against these insects. 



At Waltham, dormant applications to apples having a light infestation of over- 

 wintering red mite eggs resulted in a reduction of live mites on May 16 from 170 

 mites per 100 spurs where no treatment was applied to 39 mites per 100 spurs 

 following miscible oil 3.3 percent actual oil, and to 129 mites per 100 spurs follow- 

 ing DNOC powder at the rate of 3 pounds in 100 gallons. By August 1 no sig- 

 nificant difference in the number of mites was found, indicating that the effect 

 of the dormant spray had been lost; 



Studies of Different Forms of DDT. (A. I. Bourne and \V. D. Whitcomb.) 

 The work on DDT in its various forms was conducted in cooperation with the 

 Crop Protection Institute, and all of the materials were furnished by the Geigy 

 Company, Inc., New York City. Tests of DDT were made in all of the outstand- 

 ing field projects and are reported under those projects, and in addition special 

 laboratory and field tests were made on as many particular species of insect pests 

 as possible. 



Rose Chafer. In laboratory tests Gesarol A-20 and A-3 gave very promising 

 results against rose chafer. In the first series of tests the materials were applied 

 in a light application to grape foliage, and beetles were then placed on the leaves. 

 In 6 days 90 percent of the beetles on dusted foliage were dead and only 50 

 percent on sprayed leaves. In a second test, foliage was given a heavy dusting 

 with A-3, and 80 percent of the beetles were dead after 2 days and 90 percent at 

 the end of 3 days. In a series in which the beetles were sprayed or dusted and 

 then placed on grape foliage which was also sprayed or dusted, '90 percent of the 

 sprayed beetles and all of the dusted beetles had died by the second da}-. In a 

 fourth series, beetles were sprayed or dusted and placed on untreated grape foli- 

 age. After 2 days 80 percent of the dusted beetles and 74 percent of the sprayed 

 beetles were dead, and at the end of 5 days all had died. In this time 4 percent 

 of the untreated beetles died in the 2-day period, 2 percent more after 3 days, 

 and 10 percent at the 5-day period. 



Japanese Beetle. Gesarol A-20 spray and Gesarol A-3 dust were fully as ef- 

 fective against Japanese beetles as against rose chafer. The beetles seemed to 

 be rendered inactive within a few hours after treatment and no recovery was 

 noted. In all cases the beetles had been treated and then placed on fresh foliage. 



In a comparison of DDT with other Insecticides, all beetles treated with DDT 

 spray or dust were dead by the second day, while all were alive in lots treated 

 with cryolite spray and copper rotenone dust. In the lot treated with Lethane 

 B-72, 20 percent of the beetles were dead after 2 days and most of the remaining 

 beetles were more or less inactive. During this period of 2 days, onh- 3 percent 

 of the untreated beetles had succumbed. 



