58 MASS. EXPERIMENT STATION BULLETIN 339 



Sprays were applied to a block of young Starking trees in an infested orchard. 

 Four applications were made at the height of the oviposition period of the first 

 generation, May 20, 22, 25, and 29; and these were repeated at the corre- 

 sponding period of development for the second generation, July 7, 10, 14, and 

 17. By omitting the spray on certain trees at each application, records were 

 secured on the value of 1, 2, 3, and 4 treatments. 



On the unsprayed trees the average infestation by the first generation was 

 42.28 percent infested tips, varying on individual trees from 83 to 3 per- 

 cent. This variable infestation made conclusive deductions from the results 

 of spray treatments difficult. Average infestations in the sprayed blocks 

 varied from 19.08 to 6.3 percent infested tips, and represented a reduction 

 of 55 to 85 percent. Derris extract, summer oil emulsion, and lime-sulfur were 

 about equally efficient in reducing the number of curled leaves and were more 

 effective than nicotine sulfate and a combination of soluble and insoluble nic- 

 otine. Three and four applications were generally more effective than 1 or 2 

 treatments, and this is significant because the trees receiving 3 and 4 sprays were 

 nearer the most heavily infested unsprayed trees. 



During the spraying for the second generation, the infestation on the un- 

 sprayed trees increased to 69 percent, and the infestation in the sprayed trees 

 increased correspondingly. Summer oil emulsion gave the best protection in 

 this series with 17 percent infested tips, and the combination nicotine with 31 

 percent infested tips was the least effective. 



Adaptability of Cryptolaemus to Control of Mealybugs in the Green- 

 house. (W. D. Whitcomb and William Garland, Waltham.) Attempts to 

 hold over the mature larvae and pupae of Cryptolaemus in cold storage have 

 continued to be unsuccessful. In a room maintained at 45° F. for the cooling 

 of cut flowers, none of the 400 full-grown larvae or 200 pupae survived a storage 

 period of 2 months. When other larvae and pupae were stored in a typical cold 

 storage room at 30°-33° F., none survived exposures of 1 to 3 months. At 

 45° F. it appeared that the low temperature retarded but did not stop the 

 activity and permitted a partial development which results in death when 

 continued. 



Life history studies of the citrus mealybug continued to show that activity 

 is retarded by exposure to constant temperatures between 60° and 65° F., 

 but that development continues at a greater and more nearly normal rate at 

 these temperatures than does the development of Cryptolaemus or many 

 other greenhouse insects. 



When Cryptolaemus were confined in constant temperature cabinets, the 

 greatest activity and fastest development were at 80° F., but the average life 

 of the beetles was 7.2 days longer at 70°. A temperature of 70° was also more 

 favorable for the incubation of eggs, for larvae hatched from 49.7 percent of 

 them at 70° and from only 34.3 percent of those confined at 80°. The average 

 length of life of the larvae was 59.4 days at 70°, and 53.5 days at 80°. 



At 60° F. no Cryptolaemus larvae have been reared from hatching to pupa- 

 tion, the average life being 28.83 days, and they ate only 2.36 mealybug eggs 

 per day during that period. The feeding of the larvae at 70° and 80° was very 

 nearly equal, being only 1.4 eggs per day greater at the higher temperature. 

 The most active period of the larvae began after they had lived 20 days, when 

 they ate more than three times as many mealybug eggs per day as during the 

 first 20 days of their life. Just before pupation and before each moult feeding 

 decreased, especially at 80° F. 



