38 MASS. EXPERIMENT STATION BULLETIN 436 



for its control. Most of this fruit could be salvaged, however, and the trees were 

 in good vigorous condition going into the winter. 



Heavy Deposit-Building Dust Against Late Codling Moth. The dusts were 

 used in three applications covering the period from July 12 to August 9, which 

 spanned the period of heavy hatching of eggs and appearance of late season 

 larvae of 1st brood codling moth and of early 2nd brood larvae. 



The heavy deposit-building dust proved somewhat superior to spraying, and 

 the standard dust was approximately equal in value to spraying. Against apple 

 scab (in a season of exceptionally heavy infection) the heavy deposit dust gave 

 protection very comparable with the spray. The standard dust was less effective. 

 Late summer damage by miscellaneous insect pests was uniformly low in all 

 plots, and apple maggot injury was nil. 



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

 Some corn borer moths emerged before the corn had appeared above ground, the 

 first recorded emergence being April 30. The period of emergence was prolonged 

 over a number of weeks — considerably longer than normal— and evidently the 

 unfavorable weather interfered to such an extent with moth activity that the 

 first brood of borers was negligible. This was evidenced by the scarcity of egg 

 masses and by the record of tassel breakage, counts of which were made in the 

 experimental fields just before the crop was picked. In the check plots the per- 

 centage of infested tips was 9.5, while in the treated plots the percentage varied 

 from to 2.4, with a weighted average of 1.4 percent. The very light infestation 

 was further shown in the yield records. The yield in all plots was 1532 ears, 

 of which only 15 w^ere found infested. In all the treated plots, 1293 ears were 

 harvested, of which 1 1 (0.8 percent) were infested. Unsprayed check plots yielded 

 239 ears, of which 4 (1.7 percent) were infested. 



Even with such a slight infestation, the percentage of marketable corn in pro- 

 portion to total yield reflected the effect of the borer attack. At the first picking 

 the yield in sprayed plots ranged from 44 to 68 ears per plot; in the check plot 

 only 23 ears were ready to pick. In the treated plots 96 to 100 percent of the 

 total yield was of marketable grade; in the unsprayed check, 91 percent. 



Potato Spraying Experiments. (A. I. Bourne.) Flea beetles were normally 

 abundant early in June, and the second attack occurred in late July and August. 



No leafhopper infestation occurred, and there was no serious threat by aphids. 

 A small attack appeared in July, but an application of nicotine sulfate checked 

 it before more than a very light attack developed. 



The plots were given twelve applications between June 11 (flea beetles ap- 

 peared about June 8-9) and September 11, when no new growth was taking place. 

 No evidence of injury to vines following any of the sprays was noted. 



The most significant differences in flea beetle damage were between the DDT 

 plot (attack very light) and the Dithane plots (attack very severe). In both 

 the Bordeaux and the Dithane plots the addition of calcium arsenate materially 

 reduced the severity of attack. This was especially noticeable in the case of 

 Dithane, which appeared to give very little protection from flea beetle when used 

 alone. There was no significant difference between the two strengths of Bor- 

 deaux, but there was a very appreciable reduction in all cases where calcium 

 arsenate was used. Flea beetle damage in the DDT plot was insignificant through- 

 out the season. As the season progressed, the increased injury by flea beetles 

 in the Dithane plots indicated that the repellent action of sprays in near-by 

 plots might have driven the beetles to the Dithane-sprayed plants. The sharp 

 decline in leaf perforation following the application of calcium arsenate indicates 

 that the arsenical is essential when Dithane is used. 



