36 MASS. EXPERIMENT STATION BULLETIN 428 



tions, the value of nonarsenical insecticides to supplement the standard schedule, 

 and a study of one form of DDT (Gesarol-20) as an orchard spray mateiial. 



All materials were used in combination with wettable sulfur to determine their 

 compatibility and effectiveness in disease control. Special emphasis was laid 

 on the emergency codling moth spra>- interposed betweeq the 2d and 3d cover 

 sprays and intended to fill the gap existing between mid-June and early Julj^ 

 Records were taken from the Mcintosh variety. Fruit from these trees was 

 harvested just before the hurricane of September 14-15. Scab proved to be a 

 minor factor and was well controlled in all plots. 



Although in the unsprayed check plot 66 percent of the fruit was more or less 

 scarred by curculio, yet the spray applications timed on temperature ranges were 

 sufficiently accurate to hold the pest in check very satisfactorily except in the 

 plots where DDT replaced lead arsenate. DDT failed to check curculio and 35.6 

 percent of the fruit in this plot showed curculio damage. 



Codling moth proved to be a more difficult problem. Following the standard 

 schedule there was 15 percent injury. One application of fixed nicotine reduced 

 codling moth injury by approximately 2 percent. Two applications of fixed 

 nicotine, however, reduced injury by this species to 5 percent, and a modified 

 schedule employing DX-nicotine in combination with reduced dosage of lead 

 arsenate held codling moth injury to approximately 3 percent. An emergency 

 application interposed between the 2d and 3d cover sprays still further reduced 

 codling moth damage to 1.4 percent. 



DDT failed to check plum curculio activity to any marked degree and allowed 

 10 percent codling moth damage but proved slightly superior to the standard 

 schedule against apple maggot. 



The addition of magnesium sulfate to the spray combination, to correct mag- 

 nesium deficiency, caused no injury to leaves or russeting of fruit and had little 

 or no effect upon the toxicity of the sprays to either insect pests or plant diseases. 



A heavy deposit-building dust to protect fruit from late-season stings by cod- 

 ling moth showed definite possibilities. Codling moth damage in dusted plots 

 was only slightly more than half that in adjoining sprayed plots. The dust also 

 held scab successfulh'. 



Insecticides for the Control of European Corn Borer. (A. I. Bourne.) A large 

 second brood of European corn borer in 1943, coupled with a mild winter and 

 very little snowfall, produced one of the heaviest carry-overs of larvae in Massa- 

 chusetts in recent years. Relaxing of clean-up measures left much of the corn 

 standing in the fields, and winter mortality was practically nil. There was every 

 indication of a very heavy infestation for the 1944 season. Hot, dry weather 

 throughout May evidently retarded pupation, which was very slow until the 

 period of one or two light rains about mid-May but proceeded rapidly thereafter. 

 However, during the period of moth activity very unfavorable weather inter- 

 vened and egg laying was seriously retarded. As a result, throughout practically 

 the entire state, the infestation of early sweet corn was not serious and was ver}- 

 much lighter than anticipated. 



DDT spray (Gesarol A-20 at 2 pounds to 100 gallons) and dust (A-3) gave 

 almost perfect control. 



Black Leaf 155 at the rate of 2 pounds to 100 gallons was sufficiently effective 

 to indicate that against a light infestation this dosage would give good commercial 

 control if the application was properly timed. Black Leaf 155 at 3 pounds to 

 100 gallons dosage and derris (4 percent rotenone) spray at 4 pounds to 100 

 gallons gave better than 97 percent control. As indicated above, the infestation 

 was too light to show any significant difference between treatments. The borer 

 population in the unsprayed checks averaged only 1 to 2 larvae per plant. 



