Does fruit-tree architecture manipulation affect the development of pests and pathogens? A case study in an organic apple orchard

Summary in the original language of the document

Centrifugal training, based on the extinction procedure, is an innovative type of apple tree training recently used in French apple orchards. The thinning cut of fruiting spurs along the trunk and on the proximal and underside parts of the fruiting branches modifies the within-tree leaf density and light environment, which is likely to affect the development of some apple pests and pathogens. In this study, the development of the most serious foliar pests (aphids, mites) and disease (apple scab) was assessed over 3 years in an organic apple orchard with two training systems: the centrifugal training (CT) system, and the original Solaxe (OS) system, using a bent axis with no removal of fruiting spurs, as a control. Infestation levels were significantly lower in 2002 and 2004 in the CT system than in the OS system for the most prevalent pest, the rosy aphid, Dysaphis plantaginea, and in 2003 for the red spider mite, Panonychus ulmi. Infestation by the green apple aphid, Aphis pomi, was higher in June 2002 and June 2004 and lower in 2003 in the CT system, compared to the control. The incidence of leaf scab was lower in the CT system than in the control in Spring 2002 and Spring 2004; but, later in the Summer, it increased more in CT trees, resulting in no difference between training systems in the level of fruit infection at harvest. Hypotheses considered were based mainly on: (i) the removal of pests or inoculum due to the thinning cut of fruiting spurs for CT trees; (ii) the within-tree microclimate, providing a more aerated canopy in the CT system; (iii) the shoot density and distribution, allowing greater distances between growing shoots in CT trees; and/or (iv) the shoot growth dynamics, allowing the presence of attractive or susceptible leaves in late June. Since the most serious apple pests and diseases were less prevalent in the CT system during the 3 years of the experiment, this proved to be a complementary, but sustainable, means to contribute to crop protection, especially in organic or integrated pest management orchards.