Resistance of young ezo-spruce, Picea jezoensis, to the fundatrix of the yezo-spruce gall aphid, Adelges japonicus Monzen (Homoptera, Adelgidae).
Fecundity of the winged form of Adelges japonicus, mortality of the following generation (fundatrix), and the number of galls caused by the fundatrices were examined using individuals that were oviposited artificially on galled or ungalled young Picea jezoensis trees in a monospecific plantation (in Japan). Five galled and four ungalled trees were selected based on the number of galls formed during the six to nine years prior to the study. During this period, a large number of galls were formed on galled trees but no galls were produced on ungalled trees. Neither number of eggs deposited by the winged form, nor number of pre-overwintering fundatrices differed between galled and ungalled trees. However, mortality rates differed significantly during the overwintering period, and fundatrices became more numerous on galled trees in mid-April. As a result, the number of galls on galled trees became larger than that on ungalled trees. Results suggest that ungalled trees are resistant to infestation by fundatrix.