38 MASS. EXPERIMENT STATION BULLETIN 428 



and DDT dusts, in both cases giving higher than 88 percent reduction in the 

 number of thrips, which is a very satisfactory control. 



Of the sprays applied, nicotine sulfate with Pine Tar soap gave excellent re- 

 sults by providing an effective control of better than 97 percent. Derris powder 

 with the addition of a wetting agent (Ultrawet) ranked very close to nicotine 

 sulfate, causing 95 to 97 percent reduction in thrips population and furnishing 

 very definite residual effects which prevented reinfestation. DDT (Gesarol A-20) 

 spray alone gave 87 percent control, and when used with a wetting agent 91.4 

 percent control. All of the materials used as sprays proved entirely safe and 

 caused neither immediate burn nor any retardation of growth. 



Biology and Control of the Celery Plant Bug. (W. D. Whitcomb and Wm. 

 Garland, Waltham.) The celery plant bug {Lygiis campestris L.) was much less 

 abundant in 1944 than in the two previous years and the infestation in the experi- 

 mental plantings at Waltham was extremely light. Nevertheless, considerable 

 "blackheart" developed in the early celery, apparently due to a frost on May 19, 

 1944, followed by abnormally dry weather. Although many plants on which no 

 bugs were observed in semi-weekly observations developed "blackheart", some 

 correlation between "blackheart" and plant bugs was indicated by the presence 

 of 1 (first generation) or 2 (second generation) more bugs per "blackheart" plant 

 than on normal plants. Yellow varieties of celery averaged about 2 more plant 

 bugs per plant than green varieties; and Summer Pascal, the favorite variety in 

 this area, appeared more resistant to plant bug infestation. 



With infestations averaging about 20 pTant bugs per 100 plants, 2 or 3 applica- 

 tions of insecticides gave excellent protection. Pyrethrum dust containing .2 

 percent pyrethrins with and without sulfur, and a commercial thiocj'anate dusl 

 called B-71 gave perfect control after each application, and a .5 percent rotenone 

 dust was satisfactory. 



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



Whitcomb and Wm. Garland, Waltham.) Experimental fumigations with 

 chlor naphthalene mixtures to recheck a few critical factors in the use of this 

 material were completed. 



Preliminary fumigations with alpha bromo naphthalene showed reasonable 

 toxicity to the common red spider but also gave indications of plant injury. How- 

 ever, this material is considered sufficiently promising to warrant further investi- 

 gation. 



Biology and Control of the Grape Cane Girdler. (W. D. Whitcomb and Win. 

 E. Tomlinson, Jr., Waltham.) The grape cane girdler was naturally scarce in 

 1944, and the time allotted to this project was temporarilj' transferred to other 

 work. 



Apple Maggot Emergence. (W. D. Whitcomb.) Apple maggot flies began to 

 emerge in the cages at Waltham in 1944 on June 14, the earliest date since the 

 cages have been in operation. Favorable conditions permitted some of the flies 

 to live until early October and created an unusually long period of activity for 

 this pest. 



Cultivated Soil Sod 



First Fly Emerged June 14 June 14 



25 Percent of Flies Emerged June 23 June 26 



50 Percent of Flies Emerged July 3 July 3 



75 Percent of Flies Emerged July 14 July 13 



Last Fly Emerged June 26 June 26 



Percent of Flies Emerged 66 45 



