The effect of aphid (Dysaphis plantaginea pass., Hom., Aphididae) feeding on apple fruit growth

Abstract

Abstract The effect of feeding of the rosy apple aphid, Dysaphis plantaginea , on apple fruit and leaf growth was studied on the branches of two-year-old Golden Delicious trees grafted on M26 rootstock. There was a small influence on leaf growth. The metabolic pool model was expressed in a multiple regression model which was parametrized with observations on plant growth and aphid densities. The calculated contribution of one aphid on fruit growth was highest at low aphid and fruit densities. At high fruit densities the contribution was relatively higher at high than at low aphid densities. Subsequently, the supply-demand ratios of 0.89 covering 95% and of 0.63 covering 75% of the fruit demand were investigated at the time of peak density. In addition, the ratios were related to the influence of aphid and fruit and aphid densities. Increasing fruit number and aphid densities increased the reduction in fruit growth rates. If the fruit number exceeds about 15, the model predicted that fruit growth is reduced by more than 25% for any aphid density. These results provide some interesting insight into aphid-tree interactions, but are not readily applicable to supervised pest-control programs.