Protection of grapevine pruning wounds against Phaeomoniella chlamydospora and Diplodia seriata by biological and chemical methods

Abstract

The grapevine trunk diseases (GTDs) Botryosphaeria dieback and esca threaten the sustainability of the grapevine industry worldwide. This study aimed to evaluate and compare the efficacy of various liquid (pyraclostrobin + boscalid and thiophanate methyl) and paste (paste + tebuconazole) formulation fungicide treatments, and biological control agents (Trichoderma atroviride SC1 and T. atroviride I-1237), for their potential to prevent infection of grapevine pruning wounds by Diplodia seriata and Phaeomoniella chlamydospora in two field trials over two growing seasons. Treatments were applied to freshly pruned wounds following their label dosages recommendations. After 24 hours, wounds were artificially inoculated with 400 spores of D. seriata or 800 spores of P. chlamydospora. Isolations were made from the treated pruning wounds after 12 months to evaluate the efficacy of the treatments. Fungicide formulations were superior to Trichoderma-based treatments for the control of both pathogens during both growing seasons, with mean percent disease control of 44 to 95% for D. seriata and 46 to 67% for P. chlamydospora. Pyraclostrobin + boscalid was the most effective treatment. Trichoderma atroviride-based treatments did not reduce infection by D. seriata or P. chlamydospora compared to the untreated inoculated control in both vineyards and seasons. This study represents the first vineyard assessment of several chemical and biological treatments to protect pruning wounds against GTDs fungi in Europe and provides growers with tangible preventative control practices to minimize yield losses due to GTDs.