rosy apple aphid galls reddish-grey leaf dysaphis plantaginea pest parasitic sick insect causes loss disease of crop

abdomen affected agriculture alatae aphid aphids apple arched blisters causes closeup colonies colony crop cultivated damage decreasing deformation detail disease dysaphis farm farming fruit galls garden harm harmful insect insects leaf leaves loss malus orchards organic parasitic pest plant plantaginea red reddishgrey rosy rubrum sick small transmission underside yields