Efficacy of paste and liquid fungicide formulations to protect pruning wounds against pathogens associated with grapevine trunk diseases in Chile

Abstract

Trunk diseases are important on grapevines (Vitis vinifera L.) in most countries where grapevines are grown. In Chile, Diplodia seriata, Inocutis sp. and Phaeomoniella (Pa.) chlamydospora are the most prevalent pathogens associated with this syndrome. It has been demonstrated that fresh pruning wounds are the main infection route for fungal trunk disease pathogens. The objective of this study was to evaluate the efficacy of paste and spray fungicide applications in protecting pruning wounds against D. seriata, Inocutis sp. and Pa. chlamydospora on ‘Cabernet Sauvignon’ grapevines in two important Chilean grapevine production areas. The fungicides used in this study were benomyl, pyraclostrobin, tebuconazole, and thiophanate-methyl, which were applied as paste and liquid fungicide on fresh pruning wounds pre- and post-inoculation with mycelium plugs of the different fungal pathogens used in this study. The efficacy of the fungicides was assessed by measuring the length of the discoloration of the vascular system and percent re-isolation obtained on fresh pruning wounds. The results obtained demonstrate that infections caused by D. seriata, Inocutis sp. and Pa. chlamydospora can be significantly reduced using both paste and spray applications of benomyl, pyraclostrobin, tebuconazole and thiophanate-methyl and that the paste formulations provided a better control than spray applications. Regardless of the fungicide and application method used, the pre-inoculation treatments (performed 24 h before inoculation) resulted in better control than the 24 h post-inoculation treatments. The current study showed that Inocutis sp. can induce vascular discoloration on grapevine spurs. This study supports a broader use of benzimidazole fungicides for the control of the devastating trunk diseases in all grape productions worldwide.