ANNUAL REPORT, 1940 43 



Cranberry Root Grub (Amphico»ia vulpina). One of the cranberry grow- 

 ers made an interesting attempt to kill the grubs of this pest by flooding 

 an infested bog on May 10 with a solution of sodium cyanide, 6 ounces 

 to 100 gallons of water. The cyanide was added by a measured feed to 

 the water of the flood at the flooding gate in the form of a strong stock 

 solution. This poisoned flood remained on the bog 27 hours, and analyses 

 made from time to time showed that the poison was disseminated over 

 the bog in quite even strength and that its strength was well maintained. 

 This treatment did not harm the cranberry vines noticeably, but it killed 

 hardly 70 percent of the grubs, being very definitely less effective than 

 the usual cyanide application with pumpitig rigs and hose. It was also, 

 of course, much more costly. 



On May 15, paradichlorobenzene was used to kill these grubs. It was 

 applied with a fertilizer distributor, at the rate of 600, 800, and 1200 pounds 

 to the acre on different plots, and then covered with nearly an inch of 

 sand. It was necessary to use the chemical in crystals of the particle 

 size of very coarse salt, for larger crystals did not feed through a dis- 

 tributor well and fine ones did not sift down through the cranberry vines 

 so as to cover the bog floor beneath them evenly. The chemical slowly 

 volatilizes into a non-inflammable gas five times as heavy as air and per- 

 meates the surface soil thoroughly. The gas acts slowly and takes several 

 weeks to kill insects. In these experiments, the kill was finally practically 

 complete with 1200 pounds to the acre, and 800 pounds killed half the 

 grubs. Further experience with this treatment is needed, but it may be 

 useful on bogs that drain into public water supplies or into waters with 

 fish, where cyanide cannot be used safely. It is much costlier than the 

 cyanide treatment, the price of paradichlorobenzene being about 12 cents 

 a pound. 



Paradichlorobenzene was also applied to a large plot on August 10, at 

 the rate of 1200 pounds to an acre, and the resulting kill in this case, as 

 determined on October 7, was very unsatisfactory. 



Gypsy Moth {Porthetria dispar). Cryolite used as a spray, 6 pounds in 

 100 gallons of water, 400 gallons to an acre, and as a dust, 30 pounds to 

 an acre, was eflfective in killing the caterpillars of the gypsy moth and of 

 the false armyworm in somewhat later stages of growth than is lead 

 arsenate, but it failed to check maturing gypsy moth caterpillars. Derris 

 powder (4 percent rotenone), 15 pounds in 100 gallons of water with 2 

 pounds of soap, 400 gallons to an acre, killed maturing gypsy moth cater- 

 pillars fully as well as pyrethrum dusts and at considerably less cost. 

 Basic copper arsenate, 6 pounds in 100 gallons of water, 250 gallons to 

 an acre, was more effective in killing maturing gypsy moth caterpillars 

 than any other strictly stomach poison ever tried in our cranberry investi- 

 gations. Though it was somewhat less effective than pyrethrum and 

 derris, it probably will often be useful against the largely grown cater- 

 pillars where the crop prospect is poor and the main object is to save 

 the vines. 



Grape Anomaia (Anotnala crrans). Grubs of this species were found early 

 in May throughout a bog of 17 acres in the Wenham section of Carver. 



Black-headed Firewornv {Rhopobota). Basic copper arsenate, 6 pounds in 

 100 gallons of water, 250 gallons to an acre, failed entirely as a treatment 



^ Named by Dr. Richard Dow, Curator of Insects ot the Boston Society of Natural 

 Histor}'. 



