34 MASS. EXPERIMENT STATION BULLETIN 436 



The outstanding feature of June was excessive rainfall. Rain occurred on 17 

 days and the total rainfall for the month was 7.67 inches, a record exceeded only 

 three times since the weather station in Amherst was established. One of the 

 most severe hailstorms in recent years occurred on June 15, accompanied by 1.85 

 inches of rain. Hail knocked down some fruit and severely scarred most of 

 that which remained on the trees. The hail also caused severe breakage of 

 potato plants and the heavy rain washed some areas badly. The plots were 

 flooded for more than 24 hours and neither spraying nor cultivation could be 

 attempted for a week. 



July was marked by heavy and frequent rains. The potato plots were again 

 flooded and no spray equipment could be operated through them from July 9 

 to 23. Following this setback, plants in all but the higher areas began to turn 

 yellow and died prematurely. During this period also, blight began to appear. 

 Hot humid weather further aggravated the situation. Plants in most of the 

 plots never recovered, and yield records could be taken from only small areas of 

 higher elevation in the field. 



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



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

 ect with the Dow Chemical Company was continued in 1945, both at Amherst 

 and Waltham. 



Through the growing season, apple aphids were very scarce and there were 

 practically no leafhoppers. European red mites were not only scarce but prac- 

 tically nonexistent throughout the college orchards and commercial orchards 

 near by. It was not until about early September that there was any evidence 

 of this pest. Then a sudden outbreak occurred in which a moderate to heavy 

 infestation developed and some bronzing occurred. The attack was of com- 

 paratively short duration. 



The experimental materials, Dinitro compounds D 289, D 389, C 506, and 

 D 524, applied to apples while they were dormant, practically eliminated all 

 aphid infestation, while on unsprayed checks the infestation averaged 720 

 aphids per 100 buds. None of the materials caused any direct injury to opening 

 buds or retardation in seasonal development. 



D-542 Dinitro-ortho-cresol, at both 4 and 5 percent strengths, caused an 

 almost perfect kill of oyster shell scale on lilac. 



The outstanding feature of the season's program was the successful control 

 of the blueberry bud mite {Erophyes vaccinii) in commercial plantings by the 

 use of Dn-lU in early June. Previous to these tests no spray application had 

 been successful as a control measure. Dn-Ul, 20 ounces, plus Ultrawet spreader, 

 8 ounces, per 100 gallons reduced the number of mites per bud on the varieties 

 Pemberton and Wareham from 54 and 59 before spraying to an average of 2.5 

 mites per bud for the two varieties, within 24 hours. Some injury resulted. 



A second series of tests in which Dn was applied at strengths of 16-20 ounces 

 per 100 gallons and at 150 pounds pressure instead of 400 pounds as in the first 

 series, gave successful control of the mites in 24 to 48 hours and caused no serious 

 burning. The concentration of the spray seemed to make little difference, but 

 the reduction in pressure appeared to be an important factor in preventing 

 injury. 



In a late-season outbreak of European red mite on apples and beach plums, 

 both Dn-Ul and D-4 gave 98 to 99 percent control within 24 hours. 



Studies of Different Forms of DDT. (A. I. Bourne and W. D. Whitcomb.) 

 Materials tested were supplied by Geigy Company, Inc., and included Gesarol 

 AK-40, Gesarol A-20 (water aispersible powders), and A-5 dust. 



