ANNUAL REPORT, 1947-48 



41 



azobenzene aerosols gave 100 percent control of aphis on carnations and main- 

 tained the same effectiveness against the red spider mite. 



Experimental fumigations in a commercial greenhouse with four applications 

 of 17.5 percent azobenzene powder in a pressure fumigating can failed to give 

 satisfactory control of the citrus mealybug on gardenia, although aphis and red 

 spider mite were completely killed. The standard dosage of 2 pounds per 20,000 

 cubic feet was increased to 73^ pounds without controlling the mealj'bug. No 

 injury to gardenia plants occurred, but the blooms and the paint on the green- 

 house were noticeably stained. 



Biology and Control of the Celery Plant Bug. (W. D. Whitcomb, W. J. Gar- 

 land, and C. S. Hood, Waltham.) Although the first generation of the celery 

 plant bug (Lygus campestris L.) in July, 1947, was very small, the second genera- 

 tion in August and September was moderately abundant and control measures- 

 were necessary on many celery plantings in eastern Massachusetts. 



Life history studies showed the time for development from egg to adult was 

 18.3 days in August, and 32 days in September, the difference being due almost 

 entirely to the slow growth of the fourth nymphal instar during the cool weather 

 in late September. 



Sprays and dusts to control injury by bugs of the second generation were 

 applied August 15 and September 3. DDT wettable powder in sprays containing^ 

 0.12, 0.06, and 0.03 percent DDT gave excellent control with no significant dif- 

 ferences between the dosages, although reinfestation was prevented in direct 

 proportion to the dosage. A dust containing 0.5 percent DDT and 0.06 percent 

 pyrethrum was as effective as the sprays containing DDT. Dusts containing 

 40 percent ryania and 5 percent methoxy analog of DDT were unsatisfactory. 



The size and weight of the average celery plant were significantly correlated 

 with the injury by the celery plant bug in most control treatments, as shown in 

 the tabulation. 



Treatment 



Spray 

 DDT 50, 2 pounds per 100 gallons 

 DDT 50, 1 pound per 100 gallons 

 DDT 50, H pound per 100 gallons 



Dust 



DDT 0.5 percent-pyrethrins 0.06 percent 



DDT 3 percent 



Ryania 40 percent 



Methoxy 5 percent 



Check 



Preliminary analyses by A. F. Spelman of the Control Service showed DDT 

 residue well within the tolerance of 7 p. p.m. three weeks after treatment in July. 

 In August the residue on the stalks was satisfactory, although with the stronger 

 sprays the residue was excessive on the leaves but not on the stalks. Further 

 analyses are needed and are planned. 



Biology and Control of the Grape Cane Girdler. (W. D. Whitcomb, Waltham.) 

 Grape cane girdler beetles lived an average of 61 days when confined in cages 

 with a supply of fresh grape cants daily, and made an average of 234 feeding; 



