Aphid behaviour on healthy and on yellows-virus- infected sugar beet

Myzus persicae Sulz., M. ascalonicus Doncaster, Aphis fabae Scop. and Aulacorthum solani Kalt., when caged on sugar-beet leaves in the glasshouse preferred yellowsvirus- infected leaves to healthy ones; they chose those with the most severe symptoms on which they bred more rapidly and lived longer than on green leaves. M. persicae behaved similarly on whole plants in the glasshouse. The previous host influenced the aphid's preference. Differences between the multiplication rates of aphids on healthy plants of inbred sugar-beet varieties were eliminated or reversed by infection with yellows virus. Spraying healthy plants with either sugar solutions or hydrolysate of casein increased the multiplication rate of M. persicae, but much less than did virus infection.