254 MASS. EXPERIMENT STATION BULLETIN 271 



is of home construction, there should be at least 3 or 4 inches of cork or 

 its equivalent and this of course must be protected against moisture. Such 

 insulation saves more than its cost in saved refrigeration in one season. 

 Electric cooling of milk is entirely practicable. The machines tested are 

 convenient, reliable, and, if well adjusted, economical, although the prob- 

 able service cost and annual depreciation charge were not determined. 

 Electric milk cooling tanks are a distinct labor-saving device and are more 

 sanitary than natural ice. 



DEPARTMENT OF ENTOMOLOGY 

 A. I. Bourne in Charge 



Investigation of Materials Which Promise Value in Insect Control. 



(A. I. Bourne). Further studies were nuide of the different types of oil 

 sprays with special reference to European red mite control. Red mite in- 

 festation was comparatively light throughout all the college orchards. 

 Under such circumstances all the oils gave satisfactory control with but 

 slight distinctions between types. 



Quad and triplex nozzles proved to be as satisfactory as spray guns and 

 superior to old-type rod and nozzles. They were superior to guns in 

 maintaining a mistlike spray enveloping the trees, and coverage was prac- 

 tically as rapid. Guns were superior under unfavorable wind conditions. 



Weather conditions were favorable during the delayed dormant period. 

 The temi)erature was somewhat above normal, but not excessively so as 

 in 1929. No injury was noted following any oil spray used. 



Of the miscible oiLs, Sunoco, Scalecide and Dendrol showed their cus- 

 tomary high efficiency; well over 9.5 per cent control. Of the emulsions, 

 Kleenup at 4. gallons to 100 gave 9.5 ])er cent control, somewhat better 

 IJian results in 1929. 



Tests of miscil)le oils combined with coiuniorcial copper fungicides and 

 of soapless emulsions with lime-sulfur showed no mjury to the trees or 

 lessened insecticidal efficiency of the oils. 



Comiirehensive tests of relative coverage of different oil sprays and of 

 lime-sulfur, in a block of 15-year-old apples selected because of the 

 imiformity of size and spread of the trees, indicated a considerable super- 

 iority of the oils over lime-sulfur in material and time necessary to spray 

 the same number of trees. The differences between tlie various types of 

 oil sprays were comparatively small, and would not point to ai)i)reciable 

 {superiority of any one type over another when con.sidered on a commercial 

 basis. 



In cooperation witii Tiie Pomologx' Doparlmeiit, tests were made with 

 some of the materials or combinations of materials designed to replace lead 

 arsenate as a stomach poison or to furnish a fungicidal action equal to 

 lime-sulfur and at the same time avoid the toxic effects of tiie lead ar- 

 senate— lime-sulfur combination u])on fruit and foliage. 



Calcium arsenate in condiination with aluminum sidfate and lime-sulfur, 

 with lime-sulfur alone and with the addition of excess lime was used in a 

 block of five varieties of ajiples which included four of the so-called "New 

 England Seven", namely Baldwin, Northern Spy, R. I. Greening and Mc- 

 intosh. These sprays were compared with the standard lead arsenate— lime- 



