Efficiency of Ethion in Oil Spray against California Red Scale and Citrus Red Mite1

Abstract

Combinations of ethion with kerosene and medium-grade spray oil in aqueous mixture were tested in the laboratory. Ethion as the essential toxic agent of the kerosene mixture was very effective against eggs of nonresistant citrus red mites ( Pallollychus citri (MeG)). However, against eggs of citrus red mites resistant to organic phosphate insecticides there was a dif- fercnce of more than a 15-fold increase in the LD95. In combina- tion with kerosene, malathion is more efficient than ethion adult female California red scale ( Aonidiella aurantii (Mask.)), but in combination with medium-grade spray oil ef- fidcncies of additions of ethion or malathion were comparable. Although the efficiency of a given deposit of spray oil is in- verscly proportional to the density of the scale population, this factor is nullified by incorporating ethion or malathion in oil at a deposit level in the upper range of efficiency against independ- ent individual scale. The trial deposits of ethion and malathion in spray oil were very effective in prcventing settling of newly born scale. The selected trial dosage of medium-grade spray oil was as effective against eggs of citrus red mites resistant to organic phosphate insecticides as against those of a nonresistant population. A direct relationship between efficiency and increasing concentra- tion of kerosene in aqueous mixture with a given concentration of ethion was found for adult female California red scale, but not for nonresistant citrus red mite eggs; however, a reduction in efficiency seemed to occur when the concentration of kerosene per 100 gallons of spray mixture was below 2 quarts for scale and 1 pint for mite eggs.