A REVIEW OF PRUNING TECHNIQUES FOR PEACH TREES IN RELATION TO THE INCIDENCE OF DIEBACK AND INFECTION BY LEUCOSTOMA SPP.

Three types of pruning cut were evaluated in ‘Redhaven’ and ‘Loring’ peach orchards. Trees were pruned 1) to leave the collar, a raised area of hard woody tissue that separates the branch from the main stem; 2) flush to the subtending limb, thus removing the collar region at the point of attachment; and 3) to leave stubs, 1 to 5 cm long, of the lateral branch beyond the collar area. In West Virginia, the degree of infection by Leucostoma spp., gumming, and internal discoloration was influenced significantly by the time of pruning as well as the type of pruning cut employed. The percentage of infected cuts was greater for stub cuts made during January. Trees pruned in March, however, showed that flush cuts had a higher incidence of infection by Leucostoma spp. Generally, flush cuts had more dieback than collar cuts but less than stub cuts. Collar cuts resulted in less surface area dieback, less infection by Leucostoma spp. and less internal discoloration. In Ontario, collar cuts showed less gumming relative to flush cuts and yielded fewer isolates of Leucostoma spp. than both stub and flush cuts. Visible callus surrounded a greater proportion of the wound circumference of flush cuts than of collar cuts, and stub cuts developed no visible wound callus on the cut surface. We conclude that pruning cuts that leave a raised collar of tissue at the branch junction will result in the least infection, external dieback and internal discoloration.