ANNUAL REPORT, 1931 217 



long standing. In applifation all the oils proved to be good indicators on the 

 trees. There was no evidence of any retarding of development, tip burning or 

 killing of fruit or leaf buds following any of the oils. 



All the samples gave a very satisfactory kill of the overwintering eggs of the 

 European red mite (97 per cent or better). 



Apple Maggot Control. (A. I. Bourne). Control demonstrations were 

 continued in the ten orchards in which the growers carried out the recommended 

 program in 1930. Two additional orchards, in both of which apple n.aggot had 

 been a serious pest the previous year, were included in the 1931 tests. 



The same program was outlined for the growers as was followed in 1930. 

 Particular stress was laid upon the value of close observation of the trees to 

 detect the first appearance of the flies and their relative abundance throughout 

 the season and thus allow better thning of the sprays or dusts. Examination of 

 the Mcintosh crop at harvest showed an average of 0.9 per cent maggot injury. 

 In the ten orchards included in the demonstration for the second successive year, 

 eight of the growers earned out the program in full. Maggot injury in these 

 orchards averaged 0.5 per cent. Two of the growers carried out the program only 

 in part. Samples checked in these orchards showed 3 to 4 per cent infestation. 

 In the two new orchards included this season, maggot injury was held to a low 

 figure. Their fruit showed infestation of 0.2 and of 2 per cent. 



.In no case was excessive spray residue found on the fruit. Cirowers who dusted 

 for late applications secured fully as good results as did those who depended 

 entirely on sprays. 



A very encouraging feature of the season's results was that, without excep- 

 tion, growers in these tests secured better control of apple naggot than of any 

 other major disease or insect pest. 



Control of the Plum Curculio in Apples. (W. D. Whit comb, Waltham). 

 The activity of the plum curculio in 1931 was concentrated in the period of hot 

 weather from May 27 to June 1, inclusive, when much damage was done to 

 apples. However, the activity and development throughout the season appeared 

 to be less than usual for only 1618 niature larvae en:erged from a bushel of un- 

 sprayed dropped apples, compared to an average of 2854 for the three previous 

 seasons. 



In a study of hibernating environment, no beetles survived when buried in 

 wire cages from 3 to 12 inches beneath the surface of the soil. A small number 

 of beetles survived in cages having a protection of leaves and the survival was 

 greater among beetles which were placed in hibernation October 1 than on 

 September 5 or 15. 



^^'hen confined in constant-temperature cabinets, eggs, larvae, and pupae 

 died at 55° F., and development was greatly retarded at 65° F. The most favor- 

 able temperature appeared to be 75° F. where the development was slightly 

 faster than at 85° F. The period of growth of larvae in the apples was not greatly 

 changed at any of the effective temperatures. 



The greatest number of feeding and egg punctures bv adults occurred at 

 75° F. 



