40 MASS. EXPERIMENT STATION BULLETIN 449 



greenhouse red spider on greenhouse roses when used as a 25 percent wettable 

 powder. Infestation before spraj'ing averaged 35.6 spiders per leaf on Better 

 Times variety, and 14.8 spiders per leaf on Briarcliff. When Parathion was 

 applied as a spray at the rate of 14, H, and 1 pound (equivalent to 1, 2, and 4 

 ounces of to.xicant) per 100 gallons of water, all spiders were killed at each dilu- 

 tion. Furthermore, all spiders were killed on specimen plants protected by a 

 hood of sheeting cloth, indicating very effective toxic action from the fumes. 

 Mask and gloves were used during application. 



No spiders have been found on these plants for three months after spraying, 

 and no significant injury to the rose plants occurred. 



Apple Maggot Emergence. (W. D. Whitcomb, Waltham.) Emergence of 

 apple maggot flies at Waltham was the latest for any season since the cages have 

 been operated, and applications of spray and dust for control of this pest, conse- 

 quently, were delayed. The first fly was not found until July 6 which is 10 days 

 after the average (8-year) date. Fifty percent emergence was reached on July 

 20, and flies continued to appear until August 18, which is about two weeks later 

 than usual. 



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

 vicinity of Wakham, the plum curculio continued to be the most destructive 

 insect pest of apples. On four unsprayed trees, 594 curculio beetles were col- 

 lected by jarring between May 28 and June 18, 1947. Peak collections on June 2 

 and 16 indicated the periods of maximum activity when spraying was necessary 

 for effective control. 



In laboratory examinations the number of eggs in gravid female beetles was 

 found to average 29.6, with a maximum of 43. 



Insectary experiments using five pairs of beetles per cage, with apples as food, 

 showed 41 punctures per beetle on the unsprayed apples in the 30 days of the 

 experiment. DDT-lead arsenate killed all of the beetles in 6 days, with 2 punc- 

 tures per beetle. BHC (benzene hexachloride), 3 pounds of 6 percent gamma 

 isomer in 100 gallons of water, was about half as effective, and at 2 pounds per 

 100 gallons was unsatisfactory. The addition of HETP (hexaethyl tetraphos- 

 phate) 1-1600 prevented oviposition completely and gave excellent protection 

 for about 7 days. 



In orchard experiments involving the examination of about 18,000 apples, the 

 combination of lead arsenate 2 pounds and 50 percent DDT wettable powder 

 2 pounds in 100 gallons gave the best control and was more effective by about 

 8 percent than lead arsenate alone at either 4 or 6 pounds in 100 gallons. BHC, 

 6 percent gamma isomer, at the rate of 3 pounds in 100 gallons permitted 42 

 percent of the fruit to be stung and was unsatisfactory. The addition of HETP 

 1-1600 to lead arsenate was less effective in the orchard than in the laboratory 

 because its rapid breakdown failed to maintain protection between applications. 



Study of Naphthalene and Similar Compounds as Greenhouse Fumigants. 



(W. D. Whitcomb and W. J. Garland, Waltham.) Experimental fumigations 

 with aerosols containing a naphthalene base fumigant (Fulex) failed to satis- 

 factorily control the common red spider on carnations in one 4 or 6 hour exposure 

 (47-58 percent dead), but were effective in two successive exposures at 7-10 

 day intervals (86-100 percent dead). The aerosol was effective when discharged 

 into the upper part of the room, but not from the floor. 



Effective formulae were 25 percent Fulex concentrate with Freon and 20 

 percent Fulex-azobenzene with Freon. Addition of approximately 5 percent 

 gamma isomer of benzene hexachloride to both^'Pulex concentrate and Fulex 



