ANNUAL REPORT, 1934 47 



vious winter and consequently the extended period during which fruit was ex- 

 posed to infestation. 



Introduction of Parasites of Oriental Fruit Moth. (A. I. Bourne.) Through the 

 cooperation of the Federal Bureau of Entomology the program of introducing 

 larval parasites of the oriental fruit moth was continued throughout the peach- 

 growing sections of the State. The extremely low temperatures of the winter 

 resulted in a total loss of the peach crop throughout the State. This, however, 

 offered a rather unique opportunity to combat the fruit moth. Although the 

 fruit buds were killed and the chances of a crop were destroyed, a very con- 

 siderable percentage of the insects which attack the fruit survived and were 

 forced to remain in the twigs even in late summer when normally they would have 

 entered the fruit. Their failure to find fruit in which to develop in itself led to a 

 heavy mortality of the fruit moth larvae, while the extended period of twig in- 

 festation gave better opportunity for the larval parasites to attack the pest. 



More than 18,000 larval parasites (Macrocentrus) were liberated in the State 

 during early July, and in addition many growers purchased colonies of the egg 

 parasites to release in their orchards. 



Twig collections showed a very considerable winter mortality of the parasites, 

 especially in orchards where colonies had been released for the first time the pre- 

 vious summer. In Hampden County, where the work of introducing parasites 

 had been carried on for several years, and where they are becoming well estab- 

 lished, the percentage of survival was higher. 



Late summer twig collections showed parasites again building up successfully. 

 In the western counties, records of 70 to 90 percent parasitism were made in 

 orchards where releases had been made for several years in succession; and of 

 45 to 70 percent where colonization had been attempted for shorter periods. In 

 the eastern orchards, where the parasites had been reduced to very low numbers 

 by winter mortality, the degree of parasitism was found to average 20 to 30 

 percent in the larger orchards, while in some of the smaller orchards it ranged 

 from 50 to 70 percent. 



Potato Spraying Experiments. (A. I. Bourne.) In appreciation of the present 

 interest in potato growing, in western Massachusetts especially, and of the 

 annually increasing acreage devoted to that crop, field tests of various insecticides 

 were begun the past summer for the control of the more outstanding insect pests 

 attacking that crop. Two types of rotenone sprays and dusts, a pyrethrum dust, 

 and a commercial preparation containing calcium arsenate and a small amount 

 of calcium arsenite, were tested in a complete season's program of weekly applica- 

 tions from early June, when the plants were but two to three inches high, through 

 September when many plants had reached a length of nearly four feet. The 

 variety grown was Green Mountain. 



The different materials were used in combination with 5-5-50 Bordeaux, in all 

 applications from June to late August, after which time flea beetles had passed 

 their second peak of abundance and any danger of aphid or leafhopper attack 

 was past. From late August to October five applications of Bordeaux mixture 

 alone were made. The vines continued growing until mid-September, and re- 

 mained green until killed by frost on October 9. The plots sprayed with the 

 calcium arsenate-arsenite combination were the only ones where any injury 

 to vines was noted. Plants in these plots began to show injury by late July and 

 were dying down in considerable numbers by mid-September. 



Against flea beetles, all the rotenone products gave excellent protection. They 





