t MASS. EXPERIMENT STATION BULLETIN 347 



DEPARTMENT OF ENTOMOLOGY 

 A. I. Bourne in Charge 



Investigation of Materials which Promise Value in Insect Control. (A. I. 



Bourne and W. D. Whitcomb, Waltham.) 



Oil Sprays for Dormant Applications. The outstanding features of the winter 

 of 1936-37 were the unusually high temperature and the light snowfall. The high 

 mean temperatures of January and February have only been exceeded three or 

 four times since the weather records were first taken in 1889. The weather during 

 March, however, was somewhat colder than usual and there was very little devel- 

 opment of fruit buds, so that by early April the season was approximately normal. 

 The snowfall was light throughout the entire winter and most of it melted soon 

 after it appeared; consequently, by early spring the ground was clear of snow, 

 free from frost, and conditions in the orchards for spraying were the best in years. 



During April the normally cool weather was interrupted by occasional very 

 warm days which stimulated rapid development of fruit buds. These warm periods 

 were often followed by sudden drops to comparatively low temperatures. Growers 

 found it difficult to cover their orchards in time, and considerable oil injury to 

 the opening buds occurred as a result of the low temperature immediately fol- 

 lowing application. 



European red mite was so scarce in the college orchard that there was not 

 sufficient material on which to check the efficiency of different oil sprays. Most 

 of the trees showed no infestation at all. One new type of oil, which had just 

 appeared on the market, was tested as to its relative safety on different varieties 

 of fruit trees. This oil spray comprised a mixture of 96 percent petroleum oil and 

 4 percent phenol derivatives. It contained no emulsifying agent but was prepared 

 for spraying by the addition of a goulac-bentonite emulsifier to the water before 

 the oil was poured into the spray tank. The use of such an oil involved extra steps 

 in preparation. The final spray mixture, however, proved very stable and no 

 injury to buds or retardation in seasonal development was evident. 



Substitutes for Lime-sulfur in Summer Sprays for Orchards. These tests were 

 conducted in cooperation with the Departments of Pomology and Botany. Two 

 copper fungicides were used in post-blossom sprays following the standard spray 

 program through the calyx application. One of these was also used throughout 

 the season. Liquid lime-sulfur 2-100 with spray catalizer, 2 pounds in 100 gallons, 

 was used in pre-blossom and calyx sprays, and wettable sulfur thereafter. Spray 

 catalizer is a spreader, sticker, and corrective agent in the lime-sulfur-lead arsenate 

 combination. Tests were continued with diminishing strength lime-sulfur at 

 1-50 strength in pre-pink, 1-60 in the pink and 1-75 in the calyx, to secure adequate 

 scab control and avoid injury to foliage. A mixture of dry lime-sulfur and 325- 

 mesh sulfur was applied in a complete schedule throughout the season. All of 

 these materials were used in combination with lead arsenate at the strength of 

 4 pounds per 100 gallons in the calyx, 1st and 2d cover sprays; 3 pounds per 100 

 gallons in the pre-pink, pink and 3d cover; and 2 pounds per 100 gallons in the 

 4th cover. They were also compared with the standard spray program recom- 

 mended for Massachusetts, including liquid lime-sulfur in the pre-blossom and 

 calyx sprays and wettable sulfur thereafter. Because of the prevalence of scab 

 an emergency application of fungicides was made on June 22 between the 2d 

 and 3d cover sprays. 



Characteristic spotting and crimping of the leaves followed the application 

 of the copper sprays on all varieties; also considerable russeting of fruit. There 



