Efficiency of a Re-Formed Oil Against Citrus Red Mite Eggs and California Red Scale12

Abstract

Various considerations of a potential commercial source of plant spray oils of a new hydrocarbon type given the designation “re-formed” made it interesting to investigate its efficiency against citrus red mite eggs, Panonychus citri (McGregor), and California red scale, Aonidiella aurantii (Maskell). LD95 values were calculated from laboratory dosage-mortality spray trial data by a computer using the maximum likelihood solution of probit analysis. This was done for fractions of re-formed oil and for those of a highly paraffinic oil refined by processes based on solvent extraction with exhaustive acid finishing treatment. The critical molecular size of the 2 oils for California red scale appears to occur in the same area of distillation; slightly better efficiency of the re-formed oil is indicated by lower LD95 values. Against citrus red mite eggs LD95 values are distinctly lower for the re-formed oil than for the paraffinic for 50% distillation temperatures above 650°F at 760 mm; below this to 620°F the LD95 is lower for the paraffinic than for the re-formed. This phenomenon appears to be associated with a difference in the percent paraffinicity of the re-formed fraction 1 in comparison with the others. These comparisons of efficiency are made for applications utilizing an emulsifier soluble in the oil; with its use a decrease in the critical molecular size of the highly paraffinic oil against citrus red mite eggs was found in comparison to previous results obtained with blood albumin spreader. Careful and intensive studies of properties of selected fractions of the 2 oils by currently available analytical procedures did not disclose any differences of sufficient magnitude to account for the differences in efficiency.