46 MASS. EXPERIMENT STATION BULLETIN 369 



snowfall in March and cold, wet, and generally disagreeable weather during most 

 of April. These combined to retard plant development and produce a season 

 10 to 14 days later than normal, while frequent high winds and sudden changes 

 of temperature interfered with the application of dormant and delayed dormant 

 sprays. 



The infestation of European red mite was very light throughout most of the 

 State and was practically nonexistent in most of the college blocks. On the 

 other hand the overwintering eggs of all species of orchard plant lice were very 

 abundant, and in the college blocks the infestation was the heaviest for many 

 years. Counts from 50 typical branches of both Mcintosh and Baldwin trees 

 showed 9,635 eggs on 918 inches of twig on Mcintosh, or an average of 10.5 

 eggs per linear inch; and 6,225 eggs on 683 inches of twig on Baldwin, an average 

 of 9.1 eggs per linear inch. 



In a cooperative project with the Dow Chemical Company, tests were made, 

 in the college orchard, of the ovicidal value of various oil sprays; one containing 

 dinitro-ortho-cyclo-hexyl phenol (DNOCHP), the oil having a viscosity of 110 

 sec. .Saybolt (the commercial Dowspray Dormant); a similar oil containing 

 dinitro-orthocresol; and a combination of a light oil, of 50 sec. Saybolt, and 

 dinitio-ortho-cyclo-hexylphenol. These sprays were prepared and furnished 

 by the Company. A home-made stock solution of a petroleum oil similar to that 

 used in the commercial DN spray above, combined with the DNOCHP powder 

 and emulsifier, was also prepared and applied. Tests were also made of a com- 

 mercial spray of this type supplied by the California Spray Chemical Company 

 (Nitro-Kleenup), and of a spray material consisting of a sodium salt of dinitro- 

 orthocresol manufactured by the Standard Agricultural Chemicals, Inc. (Elgetol) 

 and reported to contain no oil. All these sprays were applied while the trees were 

 in dormant condition. 



Comparison of sprayed trees and unsprayed checks indicated no mortality 

 to fruit or leaf buds nor any retardation of bud development. An application of 

 a commercial DN spray to a few young trees as the blossom buds were breaking, 

 however, was followed by considerable injury to both fruit and leaf buds. All 

 of the sprays proved very toxic to aphid eggs. 



Tests of both the commercial DNOCHP sprays and the home-prepared emul- 

 sion were carried on, in collaboration with Mr. Robert E. Huntley of Hanover, 

 in several commercial orchards and private estates in Plymouth County. In 

 most of the orchards rosy apple aphid had been so prevalent during recent years 

 that serious damage had been caused and in many cases the crop was practically 

 worthless. In these tests the sprays again demonstrated the fact that when 

 thorough coverage of the trees was secured very few aphids appeared, whereas 

 unsprayed trees showed from 10 to 50 aphids per bud. 



The Huntley estate offered the opportunity to observe for the first time the 

 results of dormant application of commercial DNOCHP spray on a wide range 

 of deciduous ornamentals including birch, catalpa, elm, hawthorn, lilac, maple, 

 oak, poplar, and willow including English laurel-leaf pussy willow, a tender vaiiety 

 quite susceptible to spray injury, as well as a dozen varieties of evergreens in- 

 cluding arborvitae, cedar, fir, juniper, pine, spruce, yew, and broad-leaved types 

 such as box, laurel, and rhododendron. Very little, if any, damage was noted 

 on the deciduous ornamentals sprayed, but very general injury, varying in 

 degree from slight burning to serious defoliation, resulted on practically all types 

 of evergreens. In addition to furnishing a very efficient control of those species 

 of aphids which had in the previous season attacked these ornamentals, the 

 sprays showed promising results against oystershell scale, elm scale, and tulip 

 scale. European red mite was so scarce throughout that area that no reliable 

 data could be secured. 



