ANNUAL REPORT, 1939 63 



serious. R. S. 380, a combination of Lethane and rotenone b\' Rohm and Haas, 

 diluted 1-400, gave good control of red spider but caused considerable foliage 

 injury at one of the applications. Stantex dispersing oil with rotenone and soap, 

 diluted 1-400, caused severe foliage injury after two applications and its use was 

 discontinued. 



In a third series of experimental sprayings, Dow's dinitro compound con- 

 tinued to give excellent control of red spider but caused slight foliage injury. 

 Cyclonox, diluted 1-400 in each of the four applications, was very effective. 

 Some plant injury resulted but none of it was severe or serious. R. S. 380 con- 

 tinued to give good control and was otherwise satisfactory. Bonox, a rotenone 

 material from the Bonide Chemical Company, was not effective when diluted 

 1-400, and caused slight to moderate plant injury. 



A fourth series of experiments showed that Dow's dinitro compound No. 2 

 with a diflferent spreader continued to cause a high mortality of red spider but 

 produced a moderate amount of injury in the form of marginal leaf burn. A 

 peanut oil-nicotine mixture 1-200 and a peanut oil-rotenone mixture 1-400 both 

 gave moderate kill of red spider but deposited an excessive oil residue on the 

 leaves and caused some defoliation. A Serrid rotenone spray 1-200 was safe on 

 plants but the mortality to red spider was low. Throughout this experiment, the 

 mortality of red spider was greater on the Talisman variety and least on White 

 Killarney. 



Biology and Control of the Apple Leaf Curling Midge. (W. D. Whitcomb, 

 Waltham.) The apple leaf curling midge, Dasyneura malt Kieff., was normally 

 abundant in 1939 and is not known to have spread greatly from the previously 

 known infested area. A new infestation was recorded in Shirley, Massachusetts, 

 but apparently this had been present for two years. 



Semi-weekly examinations from May 26 to October 4 showed that 49.93 percent 

 of the available bud tips were infested with midge eggs. The emergence of flies 

 and deposition of eggs was concentrated at three distinct periods, which indicate 

 the beginning of each generation of the insect: June 1 to 9 with a second peak 

 on June 20; July 7 to 18; and August 15 to 25. During the first infestation period 

 most of the new growth on a tree was infested but after June 20 the infestation 

 was confined to water sprouts which provided the only new growth available. 



The time at which midge maggots left the rolled leaves to spin cocoons was 

 considerably influenced by rainfall and was definitely concentrated in three 

 distinct periods. Of the 11,743 maggots collected in bands and cages, 27.51 per- 

 cent were taken on June 23 and 48.6 percent on August 1. Although only 302 

 maggots, representing 2.57 percent of the total, were collected on September 5, 

 this was a much larger number than was obtained at any other time after August 8. 



Under laboratory' conditions no flies emerged in 1939 from maggots collected 

 in June and July 1938 and held over winter, although about 50 percent had failed 

 to transform in 1938. However, 35 to 71 percent of the maggots collected in 

 August 1938 transformed to flies in 1939 after being held over winter under the 

 same conditions as the maggots collected in June and July. In 1939, 68 percent of 

 the maggots collected in June transformed; 52 percent of those collected in July; 

 21 percent of the August collection; and none of those collected in September. 



Soil treatments applied just before the emergence period of the flies indicated 

 that naphthalene flakes were an effective material for this purpose. Broadcast 

 application of these flakes, at the rate of 2 pounds per 100 square feet, was the 

 most effective treatment used and gave complete control in the experiment against 

 the second generation flies. An application of naphthalene flakes at the rate of 

 1 pound per 100 square feet followed by cultivation was nearly as effective and 

 gave better control than the same amount of naphthalene without cultivation. 



