72 Journal of Agricultural Research voi. xm. no. i 



were all alive but were inactive and none died within 48 hours. About 

 one-third of the insects were alive a month later. Other tests were 

 made for shorter periods of time without satisfactory results. 



Fumigation tests with hydrocyanic-acid gas^ were made on over- 

 wintering larvae in cocoons. The heaviest dosage used with natural 

 atmospheric pressure was i ounce of sodium cyanid to 100 cubic feet of 

 space for a period of one hour. With such treatment the larvae were 

 not killed. Other tests were made in which were used larvae taken from 

 the orchard in December in enlarged gummy twigs. The larvae were 

 incased in a hard mass of dried gum and leaves. They were fumigated 

 in a 25-inch vacuum with a dosage of i ounce of sodium cyanid to 100 

 cubic feet of space for one hour, and also with a dosage of double this 

 amount for two hours. Neither treatment killed all of the larvae. 



From the results obtained in the dipping and fumigation tests noted 

 above it would appear to be impossible to free infested nursery stock 

 from this insect by such means. 



Parasitism appears to play an important part in controlling the pest, 

 and the attack in the latter part of the season undoubtedly lessens 

 to an appreciable extent the number of moths emerging in the following 

 spring, but sufficient data on the percentage of parasitism occurring 

 have not yet been collected to warrant a definite statement in this regard. 



1 Tests made by Mr. E. R. Sasscer. of the Federal Horticultural Board. 



