62 MASS. EXPERIMENT STATION BULLETIN 388 



of 308 to 346 bushels per acre were recorded, while plots in the same field which 

 received bordeaux mixture yielded 420 bushels per acre. The plot which received 

 the low-calcium bordeaux plus calcium arsenate gave the highest yield — 474 

 bushes per acre, 76 percent of which was of number 1 grade. 



Introduction of Parasites of Oriental Fruit Moth in Peach Orchards. (A. I. 



Bourne.) The work of rearing parasites of the oriental fruit moth was con- 

 tinued in 1941. By agreement with the Department of Entomology of the 

 Connecticut Experiment Station, Mr. A. DeCaprio was again placed in charge 

 of the collection and shipment of breeding material for both institutions. Para- 

 sitism was comparatively high in the New Jersey strawberry fields in 1941 and 

 the season was early. Mr. DeCaprio, by benefit of his experience in past seasons, 

 was able to locate superb fields for collection. Cool weather during the shipping 

 period and rapid transit allowed the material to arrive at the laboratory in Am- 

 herst in very good condition. 



The strawberry leaf roller larvae were very nearly full grown when collected 

 so that very little migration took place after arrival in the laboratory. Emergence 

 of the parasites was such that all the orders from growers were filled by June 30, 

 and within the next few days a sufficient number of parasites emerged to duplicate 

 all original orders, fill late orders, and in most cases duplicate these. The surplus 

 material for distribution was made possible by the very proficient work of Mr. 

 DeCaprio in collecting breeding material, the very accurate estimates of para- 

 sitism, and the improved technique in the laboratory. Fifty-eight growers in 

 9 counties received a total of 140 colonies. More than half the growers received 

 their orders in half colonies to facilitate more uniform distribution in large orchards 

 or for use in small, isolated blocks. 



The warm weather, the unusually large number of hours of bright sunshine, 

 and the few rainy days during the period of liberation offered very favorable 

 weather conditions for the parasites. 



Naphthalene and Similar Compounds as Greenhouse Fumigants. (W. D. 



Whitcomb and Wm. Garland, Waltham.) A complete series of experimental 

 fumigations with a mixture of monochlor naphthalene oil 3 parts and commercial 

 flake naphthalene 1 part indicated that the vaporization of % to 1 ounce of the 

 fumigant in 1,000 cubic feet constitutes a lethal atmosphere which will kill 80 

 percent or more red spiders if they are exposed for three hours. These results 

 were obtained when the experiment was made at a constant temperature of 

 70° F. and a relative humidity of 50 percent, and also at 75° F. and 60 percent 

 humidity. At the higher temperature and humidity the mortality was about 

 3 percent higher, especially at the shorter exposures. 



A mortality of 30 to 40 percent resulted when the spiders were exposed for 

 three hours to ^ to ^ ounce per 1,000 cubic feet, and an exposure of one or two 

 hours to a lethal atmosphere killed only 15 to 25 percent. Potted carnations heav- 

 ily infested with the common red spider mite supplied the. experimental material, 

 and the fumigant was vaporized at the rate of l-i ounce per 1,000 cubic feet each 

 hour for six hours. An infested plant was entered and removed each hour during 

 the fumigation. 



Control of the Common Red Spider on Greenhouse Plants. (W. D. Whit- 

 comb, Wm. Garland, and W. E. Tomlinson, Jr., Waltham.) Life history studies 

 of the red spider on different host plants at constant temperatures were con- 

 tinued. Most of the studies were on potted snapdragon and showed that the 

 time required for development at 60°, 70° and 80° F. was approximately in a 

 3:2:1 ratio as follows: 



