38 MASS. EXPERIMENT STATION BULLETIN 339 



Cape than this or on Marthas Vineyard or Nantucket. It has done marked 

 injury in Wilmington, Mass., and in Rhode Island. 



Cranberry Spittle Insect (Clastoptera) . A spray of 5 pounds of derris powder 

 (4 percent rotenone) and 4 pounds of fish-oil soap in 100 gallons of water, 

 applied at the rate of 400 gallons an acre on June 16, gave a poor kill of the 

 nymphs in their spittle; but 6 pounds of derris powder (4 percent rotenone) and 

 4 pounds of fish-oil soap in 100 gallons of water, applied at the rate of 400 gallons 

 an acre, gave a fair kill; and 8 pounds of derris powder (4 percent rotenone) and 

 3 pounds of fish-oil soap in 100 gallons of water, used at the rate of 400 gallons 

 an acre on June 16, killed nearly all the nymphs. This last spray seems to 

 compete on even terms with nicotine sulfate in both cost and effectiveness as a 

 treatment for this pest, and, as the cost of derris is in time likely to fall much 

 more than that of nicotine sulfate, it should perhaps be preferred. 



A spray of 200 gallons of water-white kerosene an acre, applied on June 16, 

 did not kill many of the nymphs. This treatment destroyed the crop but in- 

 jured the vines only moderately. 



Gypsy Moth (Porthetria) . The nearly full-grown caterpillars were treated 

 with derris sprays with results as follows: 



1. Four pounds of derris powder (4 percent rotenone) and 4 pounds of fish- 

 oil soap in 100 gallons of water, 400 gallons to an acre, killed only 40 percent. 



2. Six pounds of derris powder (4 percent rotenone) and 4 pounds of fish-oil 

 soap in 100 gallons of water, 400 gallons to an acre, killed only 75 percent. 



Black-headed Fireworm {Rhopobota). A spray of 5 pounds of derris powder 

 (4 percent rotenone) and 4 pounds of fish-oil soap in 100 gallons of water, 

 400 gallons to an acre, killed 75 percent of the worms; 6 pounds of derris 

 powder (4 percent rotenone) and 4 pounds of fish-oil soap in 100 gallons of water, 

 400 gallons to an acre, killed 85 percent of the worms; and 8 pounds of derris 

 (4 percent rotenone) and 3 pounds of fish-oil soap in 100 gallons of water, 400 

 gallons to an acre, killed 98 percent of the worms. While this last spray is 

 very effective, it is too costly at present to compete as a treatment for this 

 pest. However, as the price of derris is likely to decline very materially as 

 time goes on, it has good long-range promise. 



Cranberry Fruit Worm (Mineola vaccinii). The following special attempts 

 were made to find a more effective insecticidal control for this pest: 



1. Undiluted high-grade pyrethrum dust (0.9 percent pyrethrin content) 

 was applied at about sunset at the rate of 100 pounds an acre to the same area 

 of a cranberry bog on each of the following dates, with the vine conditions 

 noted: 



June 29 — Vines in full bloom. 



July 5 — Vines in bloom. 



July 11 — Vines going out of bloom. 

 The dust did not appear to affect the setting of the fruit. It was estimated that 

 fruit worms took about 35 percent of the berries on the dusted area as com- 

 pared with 50 to 90 percent on untreated bog nearby. 



2. A spray of 10 pounds of derris powder (4 percent rotenone) and 2 pounds 

 of fish-oil soap in 100 gallons of water, applied at the rate of 400 gallons to an 

 acre on July 13, the vines being out of bloom, controlled the insect much better 

 than any insecticide ever tried before, it being estimated that the worms took 

 less than 10 percent of the berries as compared with 35 to 90 percent on sur- 

 rounding areas. The treatment did not seem to affect the vines or crop. 



3. The derris spray just mentioned was also used early in August on plots 

 where fruit worms were abundant. It killed fully a third of the worms in the 

 berries. 



Trichogramma minutum. Work with this important parasite of the fruit worm 



