Observations on the Reproductive Behaviour of Amphorophora rubi (Kalt.), with special Reference to the Phenomenon of Insect Resistance in Raspberries

Abstract

Sixteen varieties of Rubus, comprising four species, were tested with the Aphid, Amphorophora rubi (Kalt.), which is a vector of virus diseases of Rubus in Europe and N. America, to establish the range of resistance to the development of populations of the insect. The phenomenon of resistance was then further investigated from the aspect of fecundity, reproductive rate, length of life, growth rate and behaviour of the Aphid. In these latter investigations only four varieties of raspberry were employed. The varieties Malling Promise and Lloyd George showed no resistance. Malling Landmark proved to be highly resistant but showed a slight reduction in resistance in the autumn. Newburgh appeared to occupy an intermediate position between Malling Landmark and the other two varieties. There were indications, however, that under field conditions its degree of aphid resistance may be greater than was observed under experimental conditions. Resistance seems to involve a slowing down of the reproductive rate, a shortening of the length of life of adults and prevention of development of the nymphs. The practicability of using aphid-resistant varieties of raspberry to minimise virus spread is discussed.