ANNUAL REPORT, I'Mt) 65 



development of both the corn and the European corn borer. In Amherst 

 Htid vicinity moths began to appear during the iirst week of June and by 

 the 14th larvae appeared, approximately a week later than in 1939. Tlie 

 first sprays were applied on June 17. 



Field tests of different insecticides for corn borer control were made in 

 cooperation with the same growers as in the previous years. The variety 

 used was Golden Early Market, the same as in 1939, and the plantings 

 were made on approximately the same date. The late season, however, 

 delayed growth so that the plants were much smaller than usual at the 

 time the first spraj^ was applied, and a schedule of 5 applications at S-daj' 

 intervals was followed. The month of June closed with a 10-day period 

 of some of the coldest weather on record for that time of year, and prac- 

 tically' the same condition prevailed in early July. The corn made very 

 slow growth and was not ready to harvest until August, nearly two weeks 

 later than normal. Derris spray (4 percent roten(jne content), derris dust 

 (1 percent rotenone), dual-fixed nicotine dust, dual-fixed nicotine as a 

 spray (nicotine content equivalent to nicotine tannate). and commercial 

 prepared rotenone sprays were used in the tests. Apparently one by- 

 product of an otherwise unfavorable season was a comparatively light 

 infestation of corn borer. Yield records showed corn in the check plots 

 to be 85 percent free from borers. Derris spray gave 97.8 percent clean 

 ears, and derris dust 96 percent; dual-fixed nicotine as a dust gave 97.6 

 percent clean ears and as a spray 96+ percent. Only 11 percent of the 

 yield in the check plots, however, was of marketable grade; while in the 

 plots treated with derris spray 89.8 percent of the crop was marketable, 

 with derris dust 79 percent, with dual-fixed nicotine dust 82 percent, and 

 with dual-fixed nicotine spray 81.7 percent — a very favorable comparison 

 with unsprayed corn even in a year of light infestation. The derris spray 

 gave a reduction of 95.5 percent in borer population in the stalks as com- 

 pared with the unsprayed checks, derris dust 92.5 percent, dual-fixed nico- 

 tine dust 87.9 percent, and dual-fixed nicotine spray 75 percent. 



Studies of the relative effectiveness of different strengths of derris, in 

 the Experiment Station plots, encountered the same difiiculties mentioned 

 above — unfavorable weather conditions and vei-y slight infestation by the 

 borer. The results indicated that a dosage of 2 pounds of derris (4 per- 

 cent rotenone content) per 100 gallons was not sufficient for dependable 

 control, and that a dosage of 6 pounds to 100 gallons did not give sufficient 

 difference in control over the 4-pound strength to warrant the extra cost. 



In tests of Bancross 39 sweet corn at Waltham, five applications (June 

 17, 22, 27, July 2, 12) of powdered derris root 3 pounds and Ultrawet 8 

 ounces in 100 gallons of water produced a gain of 16 to 20 percent in the 

 number of ears free from injury by the first generation of the corn borer. 

 The ear infestation in the unsprayed plot was 22.46 percent, while that in 

 the sprayed plot was 2.67 percent where a 2-nozzle spray rod was used and 

 increased to 6.01 percent where an orchard spray gun was used. At a cost 

 of $1.89 per plot for spray materials, the sprayed plots produced approx- 

 imately 350 and 300 ears more than the unsprayed plot. 



A similar experiment was made to control the second generation of the 

 corn Itorer on late sweet corn, using Carmelcfoss seed sown on June 21. 

 Three applications of derris spray were made, on August 16, 21^ and 27, 

 and records were taken on September 11 when the ears were harvested. 

 The results showed no value for spraying, the percentage of non-salable 

 ears due to borer being 13.99 unsprayed and 14.82 sprayed. The records 



