ANNUAL REPORT, 1942 35 



killed and less than 80 percent commercially injured. The most severely injured 

 varieties were Copenhagen Market and Super-curled Savo>-; Early Jersey Wake- 

 field showed the least injury. 



Tests to determine the possibility of reducing the amounts of corrosive subli- 

 mate or calomiel in treatments for combating the cabbage maggot during the war 

 emergency showed that two applications of corrosive sublimate at 1 ounce in 15 

 gallons of water (1-1920) was equal to or more effective than two applications of 

 this material at 1 ounce in 10 gallons of water (1-1280) which is the normally 

 recommended concentration. Caloniel-talc dust containing 2 percent calomel 

 was very nearly as effective as the dust containing 4 percent calomel (the normal 

 recommendation) when applied by the mound method; but was significantly 

 inferior to the 4 percent dust when applied twice with a hand duster. 



Control of Squash Vine Borer. (\V. D. Whitcomb, Waltham.) As in previous 

 experiments, spraying with 1 percent \'olck plus nicotine sulfate 1-500 was the 

 most effective treatment. 



A rotenone-copper oxychloride sulfate dust containing .75 percent rotenone 

 was also effective and distinctly more satisfactory than a pyrethrum-yellow 

 cuprous oxide dust containing 3 percent of a petroleum solution of pyrethrins. 



A DNOCHP-gypsum compound containing 2C percent of the toxicant reduced 

 the borer infestation nearly two thirds but produced only slightly more mature 

 squash than the check. Vines treated with a calcium arsenate-copper oxychloride 

 dust (5.25 percent tricalcium arsenate) were more heavily infested with borers 

 than the untreated vines but produced the largest yield in the experiment, indi- 

 cating that a light borer infestation, especially after secondary roots have de- 

 veloped, does not seriously reduce the yield of mature squash. 



Control of Striped Cucumber Beetle. (W. D. Whitcomb, Waltham.) With the 

 existing light infestation which produced only about one tenth as many beetles 

 as in 1941, a calcium arsenate-copper oxychloride dust (5.25 percent tricalcium 

 arsenate) gave 90 percent protection to cucumbers and complete protection to 

 melons, which is very encouraging in view of restricted use of rotenone during the 

 war emergency. Rotenone-copper oxychloride sulfate dusts containing .75 per- 

 cent and .5 percent rotenone respectively were about equally effective, the 

 former giving slightly better protection on the cucumbers and the latter on the 

 melons. It is evident that the dust containing .5 percent rotenone will be satis- 

 factory if available. A pyrethrum-yellow cuprous oxide dust containing 3 per- 

 cent of a petroleum solution of pyrethrins was less effective than the rotenone 

 dusts but generally satisfactory. On the other hand the same pyrethrum dust 

 without yellow cuprous oxide gave only about 50 percent protection, although 

 the yield of melons following the treatment was the greatest in the experiments, 

 apparently because of a partial control of aphids and other sucking insects which 

 spread mosaic. 



Control of Onion Thrips. (A. I. Bourne.) In field tests with insecticides the 

 standard combination of nicotine sulfate and soap again proved superior to all 

 other treatments, giving 87 percent reduction of thrips. A commercial rotenone 

 solution proved nearly as effective and gave greater residual protection. A spray 

 composed of castor bean extractive proved ineffective, largely because of its oily 

 nature and poor wetting qualities. A pine oil derivative in a penetrating soap 

 gave 74 percent control. Its effectiveness was not materially increased when 

 derris was added. A commercial pyrethrum dust (Pyrocide) gave 70 percent 

 control, an excellent showing for dust application and good commercial control. 

 Fixed nicotine spray s were only moderately effective, but a nicotine tannate 

 spray gave 74 percent effective control. A nozzle adapted to deliver a solid-cone 



