Combining irrigation, fertilisation and pruning techniques helps control aphid populations in apple and peach orchards

Abstract: Peach green aphid and rosy aphids can develop resistance to insecticides. Alternative strategies are therefore required to control these major pests in commercial orchards. To identify the key plant variables which determine tree resistance and could be manipulated by usual cultural practices we submitted potted peach and apple trees to contrasted water and nitrogen inputs. The trees were then artificially infected and the infestation dynamic followed in line with shoot development and apex composition. The high infested shoots grew faster, developed more secondary ramifications and their apices had higher amino acid and soluble sugar concentrations than the low infested shoots. Moreover, aphids preferred trees having a small number of fast growing shoots to others, having the same number of leaves being distributed among a higher number of smaller shoots. Irrigation and fertilisation could thus be used to improve tree resistance to aphids since those techniques contribute to the control of shoot development and composition.