Protection of fruit-tree pruning wounds against silver-leaf disease by immediate spray applications of captafol

Abstract

Peach trees, which were pruned annually, had each pruning cut sprayed to wetness with 0.8% captafol immediately after pruning. After 4 years, 17.2%of these trees showed silver-leaf symptoms compared with 70% of trees in which pruning cuts had been left unsprayed. Nursery apple trees were decapitated and the cuts immediately sprayed to run-off with either 0.8% captafol or water. All trees were inoculated 1 h later by spraying the cuts with spores of Chondrostereumpurpureum (syn. Stereum purpureum) produced in pure culture. Silver-leaf disease symptoms developed in 8.3% of trees treated with captafol, and c'purpureum was re-isolated from 37.5% of the trees. All trees treated with water developed silver-leaf symptoms and all yielded C. purpureum. The appendix describes and illustrates modifications which were made to hand secateurs to facilitate the immediate spraying of each pruning cut.