Growing Conditions Influence Mite Damage on Apple and Peach Leaves

Abstract

The effect of growing conditions on the physiological damage caused by mite feeding was evaluated. Control and twospotted spider mite (Tetranychus urticae Koch)-infested `Imperial Delicious' apple (Malus domestica Borkh.) and `Redhaven' peach [Prunus persica L. (Batsch.)] trees were grown under winter and summer greenhouse conditions. Mite feeding reduced net photosynthesis (Pn) of apple in both winter and summer, with equivalent regression models (Pn on mite days). Total chlorophyll content (TCHL) was decreased, and specific leaf weight (SLW) was increased by mite feeding in both winter and summer. In peach, Pn was also reduced by mite feeding, with equivalent regression models in winter and summer. SLW was unaffected, and TCHL was reduced by mite feeding in both seasons. Transpiration (Tr) of apple and peach was inconsistently affected by mites in winter and summer. In another experiment, control and European red mite (ERM) [Panonychus ulmi (Koch)]-infested `Red-chief Delicious' apple trees were grown in the summer under both greenhouse and field conditions. ERM feeding negatively affected Pn in both the greenhouse and the field, but reductions were less under field conditions. Mites reduced Tr 28% in the greenhouse and 12% in the field. TCHL, SLW, and leaf N content (LFN) were reduced by 16%, 24%, and 26%, respectively, in the greenhouse. In the field, TCHL was not significantly reduced, and SLW and LFN were reduced by 6% and 13%, respectively.