| Abstract: | Feeding-avoidance response of the bulb mite Rhizoglyphus robini to various insecticidal and acaricidal pyrethroids and some of their cleavage products was examined using a two-choice cellulose disc bioassay. The mites were able to detect extremely low quantities of certain pyrethroids, down to 1–5ng of pesticide applied to a cellulose disc weighing 200 mg. The phagodeterrent potency of the pyrethroids was found to be in the following decreasing order: fenvalerate > cypermethrin > deltamethrin > bioresmetnrin > pyrethrin > bifenthrin > cis-permethrin > trans-permethrin. Fenpropathrin, bioallethrin, flucythrinate and tetramethrin were stimulatory up to a level of 50 ng disc?1. A 100-ng dose of fenpropathrin deterred the mites. Chemical and photochemical cleavage products of pyrethroids possessed phagodeterrent potencies comparable to those of the intact pesticides. 3-Phenoxybenzotc acid and cis-chrysanthemic acid were the most effective deterrents followed by dibromochrysanthemic acid and the cis and trans bifenthrin acid moiety. The probable relevance of the observed phagodeterrence by pyrethroid residues and their cleavage products, as related to induction of dispersal and eventual outbreaks of mites, is discussed. |
