Published online by Cambridge University Press: 09 March 2007
Ninety-nine and 476 clones of Myzus persicae (Sulzer) were sampled on tobacco at Kyoto (Shimogamo) (1996–2000) and at 23 other localities (1998–1999) in Japan, respectively. The clones were classified into colour-esterase forms, distinguished by combinations of body colour and electrophoretically detectable esterases, to verify the changes in genotypic composition during the past two decades. Fifteen and 31 colour-esterase forms were found at Kyoto (Shimogamo) and at 23 other localities, respectively. Fourteen (representing c. 95% of the total clones sampled) and 24 (c. 44%) colour-esterase forms, respectively, were different from those found on tobacco during 1978–1985. The frequency of the green form and the very highly insecticide-resistant form increased. More than half of the colour-esterase forms found in the present survey were newly detected. The factors associated with these changes are discussed.