The effect of foliar fertilizers on the occurrence of apple scab [Venturia inaequalis Cooke Aderh.]

Abstract

Apple scab caused by Venturia inaequalis is the most serious fungal disease of apple in Poland. The strategy for apple scab control relies mostly on multiple applications of fungicides, usually 8 to 15 times each gr owing season. Because of the reduction in the range of fungicides and the problem with resistance, alternative methods are being searched for to help control this disease. The objective of this work was to study the effect of different foliar fertilizers f rom Intermag Co., commonly used in apple orchards, against apple scab. Experiments were conducted in 2008 and 2009 on apple trees cv. McIntosh, very susceptible to V. inaequalis . In both seasons, which were favourable to apple scab infections, a significan t reduction in the occurrence of the disease was observed after the applications of a mixture of Chelat Cu 12 Forte + Bormax + Chelat Zn 14 Forte, Alkalin KB + Si, and Alkalin PK. These fertilizers reduced disease severity by more than 80% when used at the highest of the tested concentrations (2%), and by 60% when used at lower concentrations. Two products, Alkalin KB + Si used at 2% and a 1.0% copper solution were phytotoxic to both the leaves and fruits. The results obtained showed that some of the common ly used foliar fertilizers can be useful for controlling apple scab because they cause a reduction in disease intensity (by approx. 70%