ANNUAL REPORT, 1943-44 35 



deaux plot, 35 percent greater. This would indicate that, regardless of the copper 

 content, in any low-calcium bordeaux the addition of calcium arsenate is impor- 

 tant for protection against flea beetle attack. 



In general, increased yields were recorded in the plots where calcium arsenate 

 was added to the bordeaux. In one small plot which received a low-copper - 

 high-calcium bordeaux, the yield fully equalled that in the standard 4-4-50 bor- 

 deaux plot. 



Castor Bean Extractives. (A. I. Bourne.) Preliminary tests of an insecticide 

 based on extractives of the castor bean plant with ricine as basic constituent 

 showed that the material had excellent wetting and spreading qualities, even on 

 plants with a waxy surface such as onions. As a contact spray against certain 

 species of aphids, the material has shown very definite promise. Several tests 

 were made to check the tolerance of various types of garden plants and orna- 

 mentals, and In no case was any injury to foliage noted. 



The material showed fairly good results against onion thrips. Apparently all 

 that were actually hit by the spray were killed; in other words, all those which 

 were feeding exposed on the leaves. 



The material seemed to have a repellent effect, as there was very little evidence 

 of feeding by the Mexican bean beetle after it was applied. 



Control of Onion Thrips. (A. I. Bourne.) There was a comparatively light 

 infestation of thrips in the Connecticut Valley in 1943, and most of it was well 

 distributed over the fields of set onions. The combination of thrips migration 

 in middle and late July and hot, dry weather in early August promoted a rapid 

 increase In thrips population on seed onions, which was maintained at a high 

 level until well beyond mid-August. 



A dinitro dust prepared for use on growing plants reduced the number of thrips 

 from 31 per plant to 3, a 91 percent reduction. The application was heavy and a 

 slight trace of burn was noted. The material gave definite promise. 



The standard combined spray of nicotine sulfate and soap gave 90.2 percent 

 reduction of thrips. Derris and Ultra wet reduced thrips from 100 per plant to 

 14, an 87 percent reduction, and also showed a pronounced residual action. A 

 dinitro spray (prepared for summer use) proved 92 percent effective but showed 

 little residual effect. A new antimony compound furnished for experimental use 

 by the Crop Protection Institute showed good killing action but possessed some- 

 what inferior wetting and spreading qualities on the smooth waxy leaves of onion. 

 In spite of this handicap it gave 84 percent Immediate reduction In the number 

 of thrips and reinfestation was slow. 



Control of Cabbage Maggot. (W. D. Whitcomb, Waltham.) For the second 

 consecutive year. Early Jersey Wakefield cabbage showed definite resistance to 

 injury by the cabbage maggot, 87 percent of the plants being commercially un- 

 injured, while seven other varieties of different types suffered from 20 to 64 per- 

 cent more injury. Golden Acre, with only 23 percent commercially uninjured 

 plants, showed the greatest damage. 



The first eggs were found on Ma^' 10, 1943, and the general field Infestation 

 was moderate, 77 percent of the untreated plants being commercially Injured. 



The most effective treatment was the application of calomel-talc dust In a 

 mound around the stem of the plant. Perfect commercial control was obtained 

 from dust containing either 4 percent calojnel or 2 percent calomel, although the 

 4 percent calomel-talc dust gave 10 percent more actual protection than the 2 

 percent dust. Corrosive sublimate solution in two applications at weekly inter- 

 vals gave good control at concentrations of 1-1280, 1-1920, and 1-2560. For 



