Studies on the susceptibility of varieties of apple to the feeding of two strains of woolly aphis (Homoptera) and relation to the chemical content of the tissues of the host

Abstract

Two strains of woolly aphis have been demonstrated in South Australia, the one ('Blackwood strain') able to attack varieties of apple resistant to the other ('Clare strain'). Both strains display well-defined differences in the ease with which they can colonize different varieties of apple and different parts of any one variety. These differences tend to be related to the composition of the tissues with respect to α-amino nitrogen and phenolics, but the most clear-cut correlation is an inverse one between the susceptibility of tissues and the ratio of phenolics to α-amino nitrogen in the tissue.