ANNUAL REPORT, 1932 33 



beetle was 41 at 55°, 169 at 65°, 240 at 75°, and 332 at 85° P., while the greatest 

 oviposition in one day was 22 at 85° F. 



Development of the immature stages was not completed at 55° and was very 

 slow at 65° F. At 75° all development increased rapidly, and a slight additional 

 stimulation occurred at 85° F. 



When the beetles had only poisoned apples for food, the average number of days 

 which they lived decreased with each increase in temperature and with each in- 

 crease in concentration of lead arsenate from 3 pounds in 100 gallons to 4, to 5, to 

 6 pounds. The number of days in which the poison killed the beetles was quite 

 consistent at the two higher temperatures, but at 55° and 65° F. the time was much 

 more variable among individuals. The activity of the beetles was inconsistent 

 when feeding on fruit sprayed with the lowest concentration of lead arsenate, but 

 at the higher concentrations the average number of punctures per beetle before 

 death decreased from 4.5 on 4 pounds to 3.3 on 5 pounds to 2.3 on 6 pounds of 

 lead arsenate per 100 gallons of water with no consistent variation In respect to 

 temperature. With one exception the average number of eggs per beetle was less 

 than two in all fruit sprayed with lead arsenate at the rate of 4 pounds or more per 

 100 gallons. In the majority of the experiments no eggs were laid in sprayed fruit 

 more than two days after the first activity took place. 



The comparative effectiveness of spray and dust for the control of the plum 

 curculio In apples was studied on Gravenstein at Westford. Applications were 

 made by the grower at the recommended time. Examination of 43,568 apples 

 showed 6.45 per cent of the dusted apples with curculio punctures and 2.80 per 

 cent of the sprayed apples. A similar percentage in favor of the spray treatment 

 was apparent in both the dropped fruit and harvested fruit. 



Naphthalene as a Fumigant for the Control of Greenhouse Insect 

 Pests. (W. D. Whitcomb.) Experimental fumigations with vaporized naphtha- 

 lene in a tight chamber at the rate of 1| ounces in 1,000 cubic feet resulted in 

 practically perfect control of red spider nymphs and adults from one fumigation of 

 six hours at 80° F. with relative humidities of 90, 80, 70, and 60 per cent. Two 

 and three fumigations at 75° F. gave perfect control at each relative humidity. 

 However, one fumigation at this temperature gave perfect control only at 90 per 

 cent humidity, and the mortality decreased with each decrease in relative humi- 

 dity from 80 to 60 per cent. 



When the dosage was diminished to 1 ounce In 1,000 cubic feet the control 

 was consistently satisfactory only after three fumigations, especially at 60 per 

 cent relative humidity. The natural mortality of the red spider on these plants 

 averaged 13.5 per cent. 



The mortality of red spiders when exposed without napthalene for six hours to 

 the humidities used in fumigating increased with each increase in relative humidity 

 and with each additional exposure. Two exposures of six hours at 80° F. and 90 

 per cent relative humidity killed over 50 per cent of the red spiders without 

 napthalene. 



Biology and Control of the Carrot Rust Fly. (W. D. Whitcomb.) The 

 potential infestation by the carrot rust fly in 1932 was 8.07 pupae per square foot 

 where carrots were left in the ground over winter and was almost identical with a 

 similar count (8.16) in 1931. However, the abnormally dry weather during June 

 and July practically eliminated economic injury and prevented the building up of a 

 normal second generation Infestation. This condition was at least partially 

 explained when none of the eggs confined at a constant temperature of 85° F. 

 hatched while 85 to 90 per cent of them hatched between 55° and 75° F. No 



