58 MASS. EXPERIMENT STATION BULLETIN 388 



In 1941 twelve varieties of cabbage were plaiilefl to fictermiiie their nntural 

 susceptibility to cabbage maggot injury. The results indicated that the early 

 maturing varieties such as Golden Acre and the Savoy types were most sus- 

 ceptible, and the red varietie*^ most resistant. Dry weather in the latter part of 

 the growing season interfered with the records on head development, but Red 

 Acre with 64.83 percent large and medium heads withstood the maggot injury 

 and drought the best, while Golden Acre, which suffered the most maggot injury, 

 gave the poorest yield with 7.69 percent marketable heads. 



Susceptibility of Cabbage Varieties to Cabbage Maggot Injury, Wnlthum, Mass., 194L 



l^ery Susceptible (80 percent or more commercial injur>). Golden Acre, 

 Enkhuizen Glory. 



Susceptible (65 to 80 percent conmiercial injur>). Super Curled Savo\-, 

 Cornell Early Savoy. 



Moderately Susceptible (40 to 65 percent commercial injury). — Premium 

 Flat Dutch, All Head Early, Danish Drumhead, Pearly Jersey Wake- 

 field, Pcnn State Railhead. 



Slightly Resistant (25 to 40 percent commercial iiijur\). - Mammoth Red 

 Rock, Red Drumhead, Refl Acre. 



Control of the Squash Vine Borer. (W. D. Whitcomb, Waltham.) The field 

 infestation of the squash \'ine borer was 7.52 borers per vine, which is one of the 

 greatest infestations vwr recorded in the experimental field of Blue. Hubbard 

 squash at Waltham. Experimental sprays and dusts were applied July 7, 14, 

 21, and 28. The sprats were applied at 275 pounds pressure with a small power 

 sprayer, and the dusts with a plunger t>'pe hand duster. The most effective 

 treatments were a rotenone-copper ox\'chloride sulfate dust, white oil emulsion 

 I percent with nicotine sulfate 1-500 spray, and nicotine sulfate 1-250 spra\'. 

 Rotenone -talc dust containing 0.75 percent rotenonc and a dust containing 20 

 percent cryolite with 5 percent metallic copper were moderatel}' effective. Lead 

 arsenate 3 pounds with fish oil 1 pint in 100 gallons of water as a spray was in- 

 effective, this plot having an infestation only 12 percent less than the untreated 

 check. 



Yield records showefl a significant increase in favor of the dusted plants, re- 

 flecting the beneficial action of a fungicide on the production of fruit. The plants 

 receiving the rotenone-copper o.xychloride sulfate dust yielded 594 pounds more 

 than the untreated check, an increase of 80 percent. As in previous experiments, 

 there was no consistent direct correlation between yield and borer injury. The 

 1941 experiments also strengthened the theory that an infestation of 2 borers or 

 less per vine before August 1 does not greatly reduce the yield. 



Control of Onion Thrips. (A. I. Bourne.) The early spring was characterized 

 by abnormally warm weather in April and was followed by more normal tem- 

 peratures in May with very little rain during that period. This was followed by 

 weather somewhat warmer than normal in June and rains which, although for 

 the most part small in amount, were so frequent that field crops such as onions 

 made an early start and grew rapidly. 



Such weather conditions would normalh' favor the early appearance and rapid 

 development of thrips but this was not the case in 1941. In the experimental 

 plots of seed onions, thrips appeared late and developed slowly. There were 

 practically no thrips on the plants throughout June, and by July 14 the average 

 population per plant was only 10 thrips. Very high temperature in early July 

 induced a rapid increase to the peak of 40 thrips per plant on July 21. Following 

 a rainfall of nearly one-half inch on the 25th and a heavy downpour during the 

 28th (1.9 inches) the number of thrips was reduced to approximately 12 per 



