Susceptibilities of the citrus red mite, Panonychus citri MCGREGOR, collected from citrus orchards in Saga Prefecture to several acaricides.

Abstract

Susceptibilities to seven acaricides in the citrus red mite, Panonychus citri MCGREGOR, collected from 21 citrus orchards in Saga Prefecture were determined by dipping the mite eggs in the chemical solutions. The mites collected from all orchards showed high susceptibility only to phenothiocarb. The mites from 17 orchards have low susceptibility to pyridaben which was an effective control agent of the mites from 1991 to 1992. The mite populations resistant against pyridaben have high susceptibility to phenothiocarb, suggesting no cross resistance against the two chemicals. The mites from most orchards showed low susceptibilities to other acaricides; this tendency was particularly noticeable in the mites from greenhouses of the Satsuma mandarin, Citrus unshiu. A field experiment revealed that phenothiocarb effectively reduced the mite population for 30 days in autumn. The difference in susceptibility to pyridaben among the mite populations suggest that the frequency of use of the chemical in an orchard has affected development of resistance in the mite population against the chemical.