ANNUAL REPORT, 1947-48 37 



B-542 In dormant application on cultivated blueberries gave striking control of 

 a very troublesome species of Lecanium {L. quercifex). Results with this material 

 were so nearly perfect that we hope to spray the entire blueberry plantings in 

 college plots and eradicate this potentially serious pest. This is one of the first 

 successful attempts to control this pest on blueberries. 



At Waltham, experimental applications of new materials for the control of 

 summer infestations of the European red mite were made on August 13 and 18, 

 1947, where the average infestation was 4 to 6 mites per leaf. Counts of 60 leaves 

 per treatment 10 to 14 days later showed excellent control from all materials, 

 as follows: 



Dosage Reduction 



Code Formula (per 100 of Mites 



Number gallons) per Leaf 



(percent) 



C-740 Chlorophenyl ethane and DDT 2 quarts 98.8 



C-714 Chlorophenyl ethane 1 pint 



>97 7 

 +C-726 Chlorophenyl methane 20 ounces J 



D-111 Dinitro ortho cresol 16 ounces 96.8 



Check None 5.2 



Abnormally high temperatures and prolonged drouth occurred in the period 

 covered by this experiment, and C-740 caused moderate foliage injury under 

 these conditions. 



Insecticides for the Control of the European Corn Borer. (A. I. Bourne.) 

 The first brood infestation in general was comparatively light, although some 

 fields in w^ll-protected areas in the lower Connecticut Valley showed considerable 

 damage. The second brood was more serious, and many late plantings which 

 were untreated suffered severe damage. Cold wet weather in May retarded 

 pupation, which, for the most part, took place at irregular intervals following an 

 occasional warm day. Moth emergence was correspondingly delayed and the 

 first eggs were observed about June 10. First hatching was noted about mid-June. 



Growth of corn was somewhat retarded by the same weather conditions. In 

 some fields planted April 29, the plants were just breaking ground by mid-May 

 and only reached a height of 3-4 inches during the warm period in the closing 

 days of the month. Cool weather during most of June did not improve conditions 

 greatly. Very hot weather in the last days of June and through July, however, 

 stimulated rapid growth and the earliest planted fields were ready for harvest 

 by about July 25. 



Corn borer damage in the experimental plots was not severe even in untreated 

 plots, where the average from all pickings was 85 percent clean corn compared 

 with an average of 98 percent clean corn in treated plots. However, in the check 

 plots only 75 percent of the yield was of marketable grade, and the total yield 

 averaged 35 percent more marketable ears in the sprayed plots than in the check 

 plots. The heaviest yield was on the Derris and Ryanex plots, which averaged 

 42.4 percent more ears of marketable grade than the unsprayed check plots, 

 indicating that, even with a moderate infestation, feeding of the larvae lowered 

 the vitality of the plants enough to cause not only a reduction in total yield but 

 an even more serious reduction in ears of marketable quality. 



Potato Spraying Experiments. (A. I. Bourne.) Potatoes were planted on May 

 12. May was slightly cooler than normal, with slightly more precipitation than 

 usual, well distributed over the month as light rains except for two storms on the 



