52 MASS. EXPERIMENT STATION BULLETIN 327 



a combination of soluble and insoluble nicotine will reduce the infestation 75 

 percent or more for four or five days. Application before exposure to infes- 

 tation is more effective than after exposure. The spray both repels the fly 

 and kills the eggs and newly hatched maggots. Other experiments showed 

 that derris powder in water at the rate of 6 pounds in 100 gallons plus a neutral 

 spreader is effective for several days. 



A suggested schedule of treatments which should greatly reduce the abun- 

 dance of the midge and prevent its development into a serious pest is as follows: 

 Cultivation under trees before blossom period; application of 1 pound of 

 calcium cyanide or 2 pounds of naphthalene flakes per tree just before blossom 

 period; addition of nicotine to calyx and first apple maggot sprays; and appli- 

 cation of beta-naphthol treated corrugated paper bands to trunks of infested 

 trees about June 15. 



Adaptability of Cryptolaemus to Control of Mealybugs in the Green- 

 house. (W. D. Whitcomb and Wm. Garland, Waltham.) The use of the 

 ladybird beetle, Cryptolaemus montrouzieri, Muls. to control mealybugs in a 

 large commercial gardenia range was continued under the supervision of the 

 writer. As in 1934 the activity ol a large second generation of Cryptolaemus 

 larvae in late May and early June together with favorable temperatures not 

 only controlled the mealybugs but practically eliminated them from the aerial 

 parts of the plants. It was found, however, that a small number of mealybugs 

 were living at the base of the gardenia stems protected by soil and mulch, and 

 that the ladybird beetle larvae would not burrow and kill them in such places. 

 Aided by ants, these surviving mealybugs slowly spread over the plants and 

 built up a slight to moderate infestation during the summer so that the liber- 

 ation of more beetles in the early fall or the application of artificial control 

 measures was necessary. 



Preliminary studies leading toward the development of a method for keeping 

 surplus beetles until needed were unsuccessful but provided some information 

 which will be followed in further experimentation. 



Laboratory studies of the citrus mealybug showed that although about one- 

 third more eggs were laid at 80° than at 60°, their activity at the lower temper- 

 atures is considerably greater than that of Cryptolaemus. 



Oviposition studies of Cryptolaemus beetles at controlled constant tempera- 

 tures showed an average of 63 and 61 eggs laid by each female at 80° and 70°F. 

 respectively, but only 24 eggs at 60°. It required 13.7 days for these eggs to 

 hatch at 60°, but incubation was completed in 8.28 and 4.55 days at 70° and 

 80°F. 



The value of these larvae as mealybug destroyers was studied at 60°, 70°, 

 and 80°F. by feeding larvae from birth to prepupal dormancy with as many 

 mealybug eggs as they would eat, and recording that number each day. Of 

 the 66 larvae used in this experiment only 11 were raised to larval maturity 

 and none of them in the 60° cabinet. The average number of mealybug eggs 

 eaten by each larva each day at 60° was 1.74, while the number increased to 

 8.68 at 70°, and 9.15 at 80°F. The larvae which completed their growth at 

 80° ate 1427 mealybug eggs or an average of 26.67 per day, and at 70° the 

 total was 1397.8 or 23.23 eggs per day. 



From these records it is apparent that both 70° and 80° are favorable tem- 

 peratures for Cryptolaemus activity but that 60 D or less so retards their activity 

 that these insects have little or no value for mealybug control. 



