218 MASS. EXPERIMENT STATION BULLETIN 280 



AVERAGE NUMBER OF PUNCTURES PER BEETLE PER DAY 



When the beetles were confined with poisoned fruit at the same constant 

 temperatures, the number of days they lived decreased at each succeeding 

 higher temperature, with the greatest decrease occurring between 55° and 65° F. 

 With few exceptions, the average number of punctures per beetle increased at 

 each successive higher temperature, but the rate of increase was small and 

 somewhat inconsistent. At all temperatures the average length of life decreased 

 with the increased concentration of lead arsenate until 6 pounds per 100 gallons 

 of water was used when there was a slight increase in length of life, indicating a 

 repellant action. These records indicate that 5 pounds of lead arsenate in 100 

 gallons of water was the most effective concentration to use, but the difference 

 between that and 4 pounds per 100 gallons was slight. The addition of fish oil 

 showed little effect in these experiments, but its use is advisable in field appli- 

 cations to increase adherence and spreading. A complete orchard formula con- 

 taining lime-sulfur and hydrated lime was slightly less effective at the two 

 lower temperatures but one of the best at the two higher temperatures. 



The relative effectiveness of a dust and spray program for the control of the 

 plum curculio where the fruit grower made the applications was studied under 

 orchard conditions. The sprayed block contained Gravenstein and Astrachan, 

 and the dusted block was made up of Gravenstein and Wealthy. Standard 

 treatments were applied to all trees on the same day, as nearly as possible. 

 Both blocks received liquid sprays through the calyx application. Including the 

 "drops,'' 42,440 apples were examined with the following result: 



PERCENTAGE OF .\PPLES STUNG 



\'ariety. Sprayed Dusted 



Gravenstein 8.54 9.43 



Astrachan 4.28 



Wealthy 2.90 



Total 5.74 6.12 



Biology and Control of the Carrot Rust Fly. (W. D. Whitcomb, Wal- 

 tham). As in 1930, the carrot rust fly was not present in sufficient numbers in 

 eastern Massachusetts to be considered an important pest, although reports 

 from Maine and other northern localities indicated greater numbers there. 



When confined at constant temperatures, 68 per cent of the flies emerged at 

 both 55° and 65°F.; 42 per cent at 75°; and none at 85° F. In soil with a mois- 

 ture content of 25, 50, 75 and 100 per cent of its capacity at saturation, the 

 emergence decreased from 70 per cent at 25 per cent saturation to 2.5 per cent at 

 100 per cent saturation. The average date of emergence decreased consistently 

 from May 19 with 25 per cent saturation to May 25 with 100 per cent saturation, 

 with only one individual surviving in the extremely wet soil. The flies lived 

 longest at 55° F. but laid the greatest number of eggs at 65° F., these lower tem- 

 peratures being much more favorable than the higher (75° and 85° F.). Un- 

 doubtedly temperature and moisture during the oviposition period of the first 

 generation determine the abundance of the insect in each season. The use of an 



