ANNUAL REPORT, 1946-47 33 



DEPARTMENT OF ENTOMOLOGY 

 Charles P. Alexander in Charge 



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



Bourne and W. D. Whitcomb.) Work in connection with the cooperative project 

 with the Dow Chemical Company was continued in 1946, both at Amherst and 

 Waltham. 



Dormant applications of the experimental compounds D-608, D-610, D-542, 

 D-289 and D-2 on apples, all gave excellent kill ot overwintering eggs of apple 

 plant lice. Aphids on sprayed trees averaged two or less per bud as contrasted 

 with 50 per bud on unsprayed checks. There was also measurable reduction of 

 European red mites on sprayed trees. 



Pear psylla was very satisfactorily checked by D-542 and D-2. Eggs deposited 

 on sprayed trees averaged less than 3 per fruit spur as contrasted with 80-85 on 

 unsprayed trees. No further control measures were necessary on most of the 

 pear orchard throughout the balance of the season. 



D-542 on Viburnum prevented appearance of aphids on this ornamental shrub 

 and for the first time in many years the specimens which received this spray 

 produced a full bloom, and the unsightly appearance of distorted leaves and 

 twigs was avoided. 



At Waltham applications of experimental dinitro formulations prepared by 

 the Dow Chemical Company were applied to 20-year-old apple trees when buds 

 were in the silver-tip stage. The formulae were known as D-608, D-610, and 

 D-289; and were diluted for spraying at 2 percent, 2 percent, and 2 quarts per 

 100 gallons respectively. Examinations on May 2 when the center bud was open 

 showed no rosy aphis, green aphis, or newly hatched. European red mite on any 

 ot the trees, including those unsprayed. Where D-610 at 2 percent was used, 

 very slight but insignificant injury to the most advanced fruit buds was found. 

 No injury was observed from the other formulae. 



Orchard tests of a miticidal DDT containing 20 percent hydroxy penta methyl 

 fiavan were made at Waltham and in cooperation with orchardists at Bolton, 

 Groton, and Westford, Massachusetts. When this material was used at the rate 

 of 5 pounds in 100 gallons of spra^^ careful leaf counts showed a reduction in 

 the mite population varying from 60 to 80 percent after two applications. How- 

 ever, red mite eggs were not killed and there was no toxic residue to prevent a 

 serious reinfestation in two or three weeks. 



DDT for Control of Black Scale on Gardenias in a Commercial Greenhouse, 



(A. I. Bourne.) The black scale (Saisselia oleae), a native of tropical and sub- 

 tropical regions, occurs on many types of trees dnd shrubs and is one of the most 

 serious insect pests of citrus fruits. In Massachusetts and other northern areas, 

 it is almost entirely a pest ot greenhouse plants. This scale is so prolific and has 

 such a wide range of plants upon which it will thrive, that it is always a dangerous 

 pest and, when well established, has proved very difficult to control. Aside from 

 the direct damage from its feeding, the honeydew excreted by the scales serves 

 as an excellent medium for the growth of sooty fungus. On many greenhouse 

 crops such accumulation of black, sooty fungus on the foliage constitutes a de- 

 preciation in value second only to that caused by reduction of bloom. All these 

 factors combine to make this species one to be dreaded by all commercial growers 

 who encounter it in their houses. 



