Abstract
Several preparations of “milbemycins” obtained from Streptomyces hygroscopicus subsp. aureolacrimosus were evaluated for their acaricidal effect. 1. Three fractions, A3⋅A4, B2⋅B3, and C1⋅C2 mixtures, were highly effective against all the stages of the two-spotted spider mite and the motile stage of the citrus red mite in the laboratory. Young eggs of the citrus red mite, however, were much less sensitive to these fractions as well as to the other fractions. 2. The effect of a crude preparation of milbemycins, the brown oily mixture (BOM), seemed to exert the some effect as that of all fractions contained. 3. Sublethal doses of the effective fractions and of BOM caused anesthesia in adult mites from which they recovered later. 4. BOM was easily decomposed by sun light, and its residual effect was unstable on cowpea leaves even under dark conditions. 5. BOM and petroleum oil showed a remarkable degree of synergistic activity against the eggs of the citrus red mite in the laboratory. 6. The diluent of a single EC formulation containing both BOM (0.02%) and petroleum oil (0.2%) as active ingredients was remarkably effective in controlling field populations of the citrus red mite when sprayed in mandarin orange orchards. Moreover, populations of the two-spotted spider mite on kidney bean plants in a green house were also well controlled by EC formulation containing only BOM.
