Selection of a Plant Spray Oil Combining Full Pesticidal Efficiency with Minimum Plant Injury Hazards1

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Abstract
Specifications are given for a "superior type" or paraffinic petroleum fraction of 60 seconds viscosity SUS/100°F. with an allowable range of 56 to 62 seconds for use as a plant spray oil. The specifications are based on the response of winter eggs of the European red mite (Panonychus ulmi (Koch)) to treatment. This 60-second product is believed to combine full pesticide efficiency with minimum phytotoxic hazards and is intended for use at any season. The physical and chemical tests employed to define this petroleum composition include: viscosity SUS/100°F., API gravity, unsulfonated residue, pour point and distillation range. Because of uncertainties that exist as to how the distillation characteristics of spray oils can best be defined, typical products were analyzed under both atmospheric and reduced pressure conditions. The latter procedure avoids the problem of thermal decomposition or "cracking" and appears to give more reliable results. Consequently, ASTM method D1160 conducted at 10 mm. Hg. was adopted for the distillation test in the new specifications.