38 MASS. EXPERIMENT STATION BULLETIN 441 



Apple Maggot Emergence. (W. D. VVhitcomb, Waltham.) Apple maggot fly 

 emergence in cages at Waltham occurred at about the normal period in 1946 

 although the number of maggots which survived the winter and transformed was 

 low. Emergence peaks occurred at two periods, July 7 and 25, which verified 

 the estimated dates for control by spraying. The emergence in two orchard 

 cages was: 



First fly emerged... June 29, 1946 



25 percent of flies emerged July 7-11 



50 percent of flies emerged July 14-22 



75 percent of flies emerged July 24-27 



Last fly emerged August 20 



Percent of expected emergence 68.8 



Percent of possible emergence 34.1 



Control of Plum Curculio in Apples. (W. D. Whitcomb, Waltham.) Although 

 laboratory poison studies with plum curculio beetles confined with sprayed 

 apples indicated reasonable control with DDT water suspensions containing 

 more than 1 pound DDT per 100 gallons, orchard experiments with \)/2 pounds 

 DDT per 100 gallons were unsatisfactory. Two commercial brands of DDT 

 wettable powder were compared, with almost identical results; namely, 48.47 

 and 48.54 percent of the apples stung by curculio. 



A 50 percent hexachlorocyclohe.\ane wettable powder containing 5+ percent 

 gamma isomer combined with wettable sulfur failed to control the plum curculio 

 (61.06 percent total fruit and 49.91 percent harvest fruit stung), when used in 

 the regular schedule of applications. It was evident from observations, how- 

 ever, that more frequent applications would have been significantly more ef- 

 fective. Each of the following combination treatments was significantly more 

 eflfective than lead arsenate alone in the same schedule, as shown by the per- 

 centage of harvest fruit free from stings. 



Lead arsenate 4 pounds 75.71 



Lead arsenate 4 pounds -|- DDT 50 wettable 2 pounds 97.31 



Lead arsenate 2 pounds + DDT 50 wettable 2 pounds 87.62 



Lead arsenate 4 pounds + BHC 50 wettable 2 pounds 86.90 



DDT 50 wettable 2 pounds -|- BHC 50 wettable 2 pounds 86.51 



This is the second season when sprays containing combinations of insecticides 

 have been outstandingly elTective for control of the plum curculio, and significant 

 evidence of their practical value is rapidly accumulating. 



Naphthalene and Similar Compounds as Greenhouse Fumigants. (W. D. 



Whitconib and Wm. Garland, Waltham.) Several materials were used experi- 

 mentally for the first time in an efi'ort to find a fumigant which was effective 

 against both greenhouse red spider and aphis. 



The most promising fumigant was prepared by adding small amounts of the 

 pure gamma isomer of CeHeCle to commercial Fulex paste. Addition of 1.24 

 percent, 2.48 percent, and 4.96 percent gamma isomer were equally efi'ective and 

 gave complete kill of aphids while retaining the usual high kill of red spider 

 from Fulex. 



Pressure fumigation cans containing 17.5 percent azobenzene were very ef- 

 fective against red spider and practical in spite of slight bleaching of pink flowers. 

 The addition of 10 and 16 percent azobenzene to Fulex paste was slightly less 

 injurious than the azobenzene, and effective. 



