Leaf litter is a major inoculum source for citrus diseases such citrus black spot caused by Phyllosticta citricarpa, and greasy spot caused by Mycosphaerella citri. In order to reduce this inoculum source, the efficacy of urea, dolomitic lime, a commercial compost accelerator, and an organic mulch, was assessed for enhanced leaf decomposition and reduction in sporocarps. However, due to the potential for run-off from high volume fungicide applications to disrupt leaf decomposition and microbial antagonism, the amendments were compared with and without simulated fungicide run-off. Mature green leaves of Citrus sinensis were removed from trees and placed inside mesh bags before being pinned to the orchard floor. The amendments were applied, and then simulated run-off from a typical citrus black spot fungicide program (copper, mancozeb, azoxystrobin) was applied. Leaf degradation was assessed every 2-3 weeks by visual ratings and dry weight. No direct effects on sporocarps could be observed due to insufficient infection. The results showed that the organic mulch was the most effective at enhancing decomposition, while there was significantly (P < 0.05) less decomposition in the presence of fungicide run-off.
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