46 MASS. EXPERIMENT STATION BULLETIN 327 



The emergence in 1935 was 17 percent less than in 1934. In general, in these 

 tests, flies emerged from 3 to 7 days later than in 1934 under similar conditions 

 of soil and exposure. The differences appeared to be greater in the beginning 

 of fly emergence. 



Introduction of Parasites of Oriental Fruit Moth in Peach Orchards. 



(A. I. Bourne. ) The winter of 1934-35, while not so severe as the previous one, 

 was marked by several periods of low temperature so that in most sections of 

 the State the fruit buds were killed. In many orchards trees weakened by 

 winter injury the previous year were killed outright. The oriental fruit moth 

 was greatly reduced in numbers and as a result of the severe winter and failure 

 to find fruit was nearly wiped out in many orchards. In view of this scarcity, 

 no new introductions of Macrocentrus parasites were made although some 

 growers in the southern part of the State purchased and released egg parasites. 

 Midseason collections of infested twigs showed some recovery of parasites, 

 indicating that Macrocentrus had survived the severe winter and under more 

 favorable conditions could undoubtedly establish itself successfully. 



Potato Spraying Experiments. (A. I. Bourne.) In general potato 

 flea beetles and leafhoppers were of apparently normal abundance. Leaf- 

 hoppers began to be prominent in early July and continued throughout 

 August, the hot, dry weather of late summer favoring their development. 

 Potato aphids were less abundant than usual since weather conditions during 

 early summer were unfavorable for their rapid increase. The Colorado 

 potato beetle was very scarce and its damage was negligible. Flea beetles and 

 leafhoppers, however, caused more injury than all other insects or diseases 

 combined and poorly sprayed fields suffered severely. 



Three rotenone compounds, Ku-ba-tox, Cubor and Derrisol; a barium fluo- 

 silicate compound, Dutox; and a calcium arsenate, Calrite, were used in field 

 tests the past season. All were combined with a 5-5-50 Bordeaux mixture, 

 and 14 applications were made at 7-day intervals from June 13 to September 11. 

 All tests were conducted on the standard variety, Green Mountain. 



The plants in the unsprayed check plots were badly riddled by flea beetles 

 and browned by leafhoppers and were practically all dead by the last of July. 

 The plants in the sprayed plots were thrifty and green until killed by frost on 

 October 9. The unsprayed checks yielded 179 bushels per acre while the average 

 yield in the sprayed plots was over 430 bushels per acre. 



Laboratory tests of the effect of the various sprays upon flea beetles gave 

 the following results. 



Percentage of Flea Beetles dead after — 



Material ■ — 



40 hours 62 hours 



Bordeaux mixture (5-5-50 ) 4 80 



*Ku-ba-tox 33 100 



♦Cubor 38 100 



*Derrisol 78 95 



*Calrite 30 75 



♦Dutox. 28 55 



♦Combined with Bordeaux 5-5-50. 



The rotenone products were all very effective and fully as rapid in their action 

 as Calrite. The results given by Dutox were rather unexpected since this 

 material in dust form has given a satisfactory control against flea beetles on 

 tobacco. 



