Abstract
Petroleum oils of the following types were tested in the field during the summer of 1928 for their toxicity to the White Pine Scale, Chionaspis pinifoliae (Fitch):—(l) Lubricating oil, (2) Miscible oil, (3) Three grades of highly refined “white oil.” The tolerance of the various coniferous foliages to these oils was also determined. Little difference was noticed in the toxicity of the oils (when compared at strengths sufficient for control). An oil concentration of 2.5 per cent was sufficient to give commercial control (90-100%). Highly refined “white oils” (Baume 36.6°-35.4°, Saybolt viscosity 45-85 sec/100° F.) were the only oils which could be applied (at a concentration sufficient for control) without subsequent foliage injury. The conifers tested varied in their susceptibility to oil spray injury in the following order: (1) White Spruce (most susceptible), (2) White Pine, (3) Red Pine and Scotch Pine (least susceptible). The bloom normally present on conifers disappears when an oil spray is applied. It reappears within 5-10 weeks, depending on weather conditions and the volatility of the oil applied.
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