66 MASS. EXPERIMENT STATION BULLETIN 378 



clearly show that more than three applications are necessary even if they 

 are continued nearly to harvest, since most of the infestation in the sprayed 

 corn was from recently hatched borers. The results were further con- 

 fused by a heavy infestation of corn ear worm which did not appear to be 

 affected in any way by the sprays. 



Potato Spraying Experiments. (A. I. Bourne.) Cold, wet weather dur- 

 ing spring and early summer, which prevented planting at the usual time, 

 delayed the appearance of the plants and retarded growth; subnormal 

 rainfall which persisted through August and September and an early frost 

 on September 25-26, which killed the plants in all plots, combined to form 

 a sequence of unfavorable weather conditions unusual even for New Eng- 

 land. 



The experimental plots were planted on May 21 but young placits did 

 not appear until well into June. On the east half of the plot the stand 

 was very light with many "skips" so that a considerable area had to be 

 discarded as useless for experimental purposes. Plants in all plots were 

 green and still making growth when killed by the frost of September 25. 



During the early season the infestation of fleabeetles was comparatively 

 light and little damage was done. The attack in late July, however, was 

 very heavy and there was considerable damage to unprotected foliage. 

 Leafhoppers appeared late in the season and were not verj^ numerous. A 

 heavy infestation of potato aphids was encountered in late July and early 

 August. In many fields in the Valley the abundance of aphids led to the 

 greatest build-up of several species of Coccinellid beetles which has been 

 observed for many years. In the experimental plots incipient outbreaks 

 were checked by the use of nicotine in the sprays applied July 31 and 

 August 7. In the test plots, 12 applications were made betwe'en June 20, 

 when the plants were 3 to 4 inches high, and September 4 when the flea 

 beetles and leafhoppers disappeared. Vines were killed by frost on the 

 night of September 25-26, and the potatoes were dug October 1 to 3. 



Weekh- counts of flea beetle injury showed practically no difference in 

 degree of protection from 5-2^-50 and the standard 5-5-50 bordeaux inix- 

 ture. The addition of calcium arsenate in both mixtures, however, ma- 

 terially reduced the amount of damage, especially in the plots receiving 

 low-calcium bordeaux. The growing season was three to four weeks 

 shorter than normal because of the late appearance of the plants in the 

 spring and the early frost in September. This was reflected in the yields. 

 Records of comparative yield in the different plots were of little significance 

 since plants in all plots were prematurely killed by the frost. 



Tests of commercial materials included applications of a conunercial 

 basic copper arsenate-wettable sulfur, a basic copper-wettable sulfur com- 

 bination, and a yellow copper oxide-Cherokee clay combination at dosages 

 of 1^ and 1 pound of the copper oxide per 100 gallons of spray. Against 

 flea beetle feeding both the basic copper-sulfur combinations gave excel- 

 lent protection, fully as good as that given by the standard bordeaux with 

 calcium arsenate added. The yellow copper oxide sprays furnished pro- 

 tection equivalent to standard bordeaux without arsenical. 



Records at harvest showed that plots treated with the commercial sprays 

 yielded approximately 350 bushels per acre, which was only slightly less 

 tlian the yield in the standard bordeaux plots. It is probable that greater 

 differences would have existed if early frost had not intervened, since 

 the plants in these plots were beginning to change color and die down 

 Avhile throughout the bordeaux plots the plants were still green. 



