ANNUAL REPORT, 1935 39 



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 winter of 1934-35 was marked by- 

 very low temperatures. The amount of damage caused was not so extensive 

 as in the previous year since the extreme periods were of comparatively short 

 duration. In many orchards trees on the way to recovery from the winter 

 injury of the previous year were again severely checked; and a few growers, 

 fearing that the use of oils would aggravate this condition, omitted them from 

 their spray program. No cases of oil injury were reported, however, where oil 

 sprays had been properly applied in the spring, although rather serious damage 

 was caused in at least one orchard following an application of oil spray in late 

 fall. 



Red mite infestation in the college orchard was approximately normal, but 

 uneven. In the test blocks the overwintering eggs were moderately abundant 

 so that differences in effectiveness of the various sprays were pronounced. 



The leading brands of standard commercial oil sprays again showed a very 

 high degree of control, and the number of young mites appearing on sprayed 

 trees was insignificant. 



Two new products were tested. Dendrine, a product of the Carbolineum 

 Wood Preserving Company, is a light-bodied, readily pourable material that 

 mixed readily with water, allowed excellent coverage, and was a good indicator. 

 Rawleigh's Dip and Disinfectant, a cresol-oil combination which also mixed 

 readily with water, possessed excellent spreading qualities. These were used in 

 delayed dormant application at temperatures ranging from 45° to 48°F. and 

 caused no trace of injury. Results were as follows: 



Number of Percentage of Average 



Mites per 100 Clusters Free Number of Percentage 



Treatments Leaf Clusters from Mites Mites per Leaf of Control 



Dendrine 1,248 72 1.8 79.2 



Rawleigh's Dip 2,732 60 4 54.5 



Check (unsprayed) 6,000 10 10 



Three tar washes and three commercial tar oil and mineral oil combinations 

 were applied as dormant sprays in a block of young apples. None of these 

 sprays caused any injury nor was any delay noted in bud development. These 

 results coincided with our experience with similar sprays in 1934 and, inasmuch 

 as they followed two winters marked by periods of extremely low temperatures, 

 indicate that oil sprays of this type can be used with safety in Massachusetts 

 orchards. This was confirmed by the experience of commerical growers who 

 applied such oil sprays. No opportunity was given to measure their effec- 

 tiveness against plant lice eggs because of the relative scarcity of eggs in the 

 college orchard and the heavy winter mortality of the few eggs that were 

 present. 



Spray Materials for the Control of Gladiolus Thrips. A study of the con- 

 trol of gladiolus thrips in the summer of 1935 was along two principal lines. 



1. Comparison of spray materials. Several stomach poisons including lead 

 arsenate, calcium arsenate, manganese arsenate, barium nuosilicate, sodium 

 aluminum fluoride, and a mixture of calcium arsenate and arsenite were tested. 

 These materials were used in combination with molasses alone and with 

 molasses and various wetting agents. The tests included the quality of the 



