Effects of irrigation deprivation and ground cover (Trifolium repens) in the tree row on brown rot incidence in peach
Résumé
Brown rot can lead to considerable fruit losses in peach orchards and cultural practices likely to contend this major disease have to be promoted. In order to limit peach brown rot incidence in a three-year-old mid-season maturing peach orchard of the cultivar 'Ruby Bright', four combinations of irrigation and soil management treatments were assessed: conventional (Cony) irrigation (I) and soil management (S) (Convl+ConvS); modified (Mod) irrigation and soil management (Modl+ConvS); conventional irrigation and modified soil management (Convl+ModS); and modified irrigation and soil management (ModI+ModS). Conventional irrigation and soil management in the tree row consisted of irrigation scheduling using tensiometer readings and herbicide use, respectively. Modified irrigation and soil management in the tree row consisted of water deprivation during stage III of fruit development and ground cover with white clover, respectively. For four consecutive years (2010-2013), in the conditions of the Middle Rhone Valley in France, the lowest and highest brown rot incidence were detected under (Modl+ModS) and (Convl+ConvS), respectively, whereas brown rot incidence under (Modl+ConvS) and (Convl+ModS) was intermediate. This lower brown rot incidence under the modified treatments occurred from one to two weeks before fruit maturity and was still observed for several days in post-harvest storage. Ground cover with white clover was shown to limit water availability in the soil after heavy rainfall compared to bare soil, probably limiting peach growth variations, well-known as a possible source of detrimental micro cracks at the fruit surface. This suggests that under our conditions appropriate cultural practices, water deprivation and a clover crop cover in the tree row possibly decrease peach disease sensitivity, which might lead to the reduced use of pesticide sprays to control brown rot in the orchard.