Abstract
A high level of resistance to organophosphates has evolved in the white-backed planthopper (WBPH), Sogatella furcifera HORVÁTH, as topical LD50 values were monitored from 1985 to 1987 and compared with a reference laboratory strain. The seven filed strains collected in Hiroshima Pref. from 1985 to 1987 showed high levels of resistance (9- to 37-fold) to organophosphates (fenitrothion, malathion, fenthion and phenthoate) and low levels of resistance (2- to 3-fold) to carbamates (carbryl and BPMC). The two strains collected on the East China Sea during 1986 also showed similar levels of resistance, suggesting resistance development in migration origin of WBPH. Field trials were conducted during 1986 to evaluate the effects of three conventional insecticides used against WBPH in relation to insecticide resistance. Malathion dust and fenitrothion dust applied at rates of 0.9kg a.i./ha and 0.6kg a.i./ha, respectively, were not effective reflecting resistance development against organophosphates. BPMC dust, however, applied at 0.6kg a.i./ha provided perfect control.
