60 MASS. EXPERIMENT STATION BULLETIN 369 



nearly normal in both temperature and rainfall. There were light rains well 

 distributed through the month and only three showers of more than one-half inch 

 precipitation. Corn made rapid growth throughout the month, and there was 

 little or no interruption of the spray program. 



By the first week of June, egg masses were plentiful and examination of corn- 

 fields at the college and vicinity indicated that larvae were beginning to appear 

 on approximately June 8. 



Studies of insecticidal control were conducted in cooperation with a com- 

 mercial market gardener in Hampshire County. The field tests were made in 

 his earliest planting of sweet corn, approximately one-half acre of Golden Early 

 Market. Sprays were applied five times at 5-day intervals from June 8 to 29, 

 to furnish protection throughout the period of larval appearance. An extra 

 application was made to part of the field, at the owner's request, to insure pro- 

 tection against any late-appearing larvae. 



The materials tested were derris and cube of 4 percent rotenone content; derris 

 combined with Fluxit or with cherokee clay as adhesives; two commercial sprays, 

 one containing 4 percent rotenone, and the second 23^ percent rotenone. Dual- 

 fixed nicotine and two commercial rotenone dusts were also included in the tests. 



The corn was harvested in three pickings from July 19 to 25. The infestation 

 in the unsprayed plots was heavy. Only 23 percent of the ears in the first picking 

 were borer free. The sprays, however, gave excellent protection. The cube 

 and derris plots yielded 81 and 84 percent borer-free ears respectively, and 72 

 percent of the total yield was marketable. The addition of adhesive agents did 

 not improve derris as measured in terms of clean ears but both materials allowed 

 practically the same percentage of marketable ears as in the plots where derris 

 alone was applied. The commercial 4 percent rotenone spray allowed 72 percent 

 clean ears, and 63 percent of the total yield was of marketable grades. In the 

 plots sprayed with 2.5 perce.it rotenone, 65 percent of the ears was borer free, 

 and 52.4 percent of the yield was marketable. The total yield in the unsprayed 

 checks was 40 percent borer-free, but only 32 percent of the crop was salable. 



Good commercial control was secured in the dust plots. Dual-fixed nicotine 

 allowed 77 percent borer-free ears while the two plots given commercial rotenone 

 dusts showed yields of 71 and 76 percent clean corn. The adjacent check plots 

 on the other hand showed only 40 percent borer-free ears, and only 33 percent of 

 the crop was of salable quality. 



The grower was able to salvage a larger proportion of the crop from the treated 

 plots than is indicated above since the market was rather lenient regarding size 

 and development of the ears provided they were free from borers, so that the 

 amount of corn actually marketed by the grower very closely approximated the 

 percentage of clean ears. This was not true of the corn in the unsprayed checks, 

 however, since most of the infested corn contained large, well-matured larvae 

 which had so damaged the ears that they were unfit for market. 



Potato Spraying Experiments. (A. I. Bourne.) The subnormal rainfall which 

 persisted throughout the entire growing season retarded the development of 

 potato plants in all sections of the State; was reflected in the relative abundance 

 and activity of insect pests; and, except in low areas, caused somewhat reduced 

 yields. This deficiency in rainfall was accompanied by temperatures considerably 

 higher than normal and by frequent hot, drying winds which rendered the plants 

 very susceptible to spray injury. 



Flea beetles were abundant throughout the season, particularly the second 

 brood in late July and early August. Leafhoppers were late in appearing and 

 at no time were abundant. A heavy infestation of potato aphids had developed 

 by early August, but the addition of nicotine sulfate in the sprays of August 9 



