62 MASS. EXPERIMENT STATION BULLETIN 378 



after the first eggs were found) was slightly more effective than a treat- 

 ment applied May 11 when the first eggs were found. 



Calomel-talc dust (4 percent calomel) applied at the same time as 

 the liquid treatments was very effective and produced 80 to 90 percent 

 large and medium heads, being much more satisfactory than in previous 

 seasons. 



Root treatments at transplanting were less efifective than in 1939 pro- 

 viding 70 to 90 percent control and producing 60 to 80 percent large and 

 medium heads. Pure calomel dusted on the roots gave perfect commer- 

 cial control of the maggots but produced 36 percent small heads, the 

 greatest number of any treatment, indicating some plant injury. 



A direct comparison between fibrous talc and pyrophyllite talc as a 

 carrier for 25 percent and 50 percent calomel used as root treatments 

 favored the pyrophyllite by 10 percent, both in maggot control and in the 

 production of large and medium-sized heads. 



Control of Squash Vine Borer. (W. D. Whitcomb, Waltham.) Al- 

 though the emergence of the squash vine borer nlotll^ was 10 days later 

 than normal, the field infestation of 7.45 borers per vine in the experi- 

 mental field of Blue Hubbard squash at Waltham was the heaviest that 

 has occurred in the last five years. 



Experimental control treatments using three dusts and three sprays 

 were applied July 10, 18, 24 and 31. The dusts were applied with a hand 

 duster. For applying the sprays, a hand wheelbarrow sprayer at about 

 100 pounds pressure was used for the first treatment and a power sprayer 

 at 250 pounds pressure for the other applications. 



In spite of the heavy infestation, rotenone-talc dust, a spray of nicotine 

 sulfate 1-500 plus oil emulsion 1 per cent, nicotine sulfate spray 1-250, 

 and copper-rotenone dust all reduced the number of borers per vine 79 

 percent or more. The differences between these treatments were insig- 

 nificant, but the greatest protection was obtained from the rotenone-talc 

 dust (.75 percent rotenone) and the spray of nicotine sulfate 1-500 plus 

 oil emulsion 1 percent, with 83.22 and 82.96 percent reduction respectively. 

 A commercial calcium arsenate-copper uxide dust and a commercial 

 rotenone extract spray were not effective. 



Yields in the experimental planting were very low owing to unfavorable 

 growing conditions and to a late infection of bacterial wilt. Under these 

 conditions the best yields were obtained where a commercial copper- 

 rotenone dust and a commercial calcium arsenate dust were applied, and 

 it was apparent that the yield was improved more by the fungicidal 

 action of the copper than by maximum control of the squash vine borer. 



Control of Onion Thrips. (A. 1. Bourne.) Unusually cold, wet 

 weather in April and throughout most of May delayed both planting and 

 germination of (anions. In the experimental piuts the plants were very 

 late in appearing and made very slow growth until well into July. The 

 abnormally cold, cloudy weather in late June and early July also delayed 

 the appearance of thrips and retarded their development. Many fields of 

 set onions were practically free from thrips up to mid-July when the sets 

 were pulled. The abrupt appearance of hot weather in late July provided 

 conditions more favorable for both the growth of the seed onions and 

 the increase of thrips. In the 10-day period from July 21 to 31, the daily 

 temperature reached 83° F. or higher, and during the 5-day period from 



