Fungicide control of Gnomoniopsis smithogilvyi, causal agent of chestnut rot in Australia

Chestnut rot caused by Gnomoniopsis smithogilvyi is considered a severe threat to the production of chestnuts from European chestnut (Castanea sativa Mill.) in Australia and overseas. Currently, most of the control strategies are applied post-harvest and little is known about the use of fungicides to reduce nut infection in orchards early in the season. This research evaluated the effectiveness of various fungicides against the pathogen in vitro and selected the most effective products for field trials. In vitro experiments showed that pyraclostrobin and difenoconazole-based fungicides effectively inhibited conidial germination and mycelial growth, respectively. The field trial showed that both active ingredients combined were more effective than single applications in suppressing the level of nut infection caused by G. smithogilvyi. Based on our results, using the selected fungicides can be an additional tool for growers to complement their current practices in the control of chestnut rot. To the best of our knowledge, this is the first study focused on the effectiveness of chemical treatments against G. smithogilvyi.