Evaluation of biological control agents for the protection of almond pruning wounds against infection by fungal canker pathogens

• Published in: Phytopathology Vol. 113; no. 8; pp. 1417 - 1427
• Main Authors: Travadon, Renaud, Lawrence, Daniel P, Li, Sampson, Trouillas, Florent
• Format: Journal Article
• Language: English
• Published: United States 01.08.2023
• Subjects: Disease Control and Pest Management; Biological Control; Fungal Pathogens
• ISSN: 0031-949X; 1943-7684
• DOI: 10.1094/PHYTO-02-23-0075-R

Fungal canker pathogens of almond initiate infection in trees primarily through pruning wounds. Biological control agents (BCAs) have the potential to provide long-term protection of pruning wounds by colonizing the wound surfaces and underlying tissues. Laboratory and field tests were performed to assess the efficacy of various commercial and experimental BCAs as wound protectants against almond canker pathogens. Four Trichoderma-based BCAs were evaluated using detached almond stems in the laboratory against the canker pathogens Cytospora plurivora, Eutypa lata, Neofusicoccum parvum and Neoscytalidium dimidiatum. Results indicated that Trichoderma atroviride SC1 and T. paratroviride RTFT014 significantly reduced infections by all four pathogens. The ability of these four BCAs to protect almond pruning wounds against E. lata and N. parvum were further evaluated in field trials using two almond cultivars and during two consecutive years. Both T. atroviride SC1 and T. paratroviride RTFT014 protected almond pruning wounds against E. lata and N. parvum as efficiently as thiophanate-methyl, the recommended fungicide for treatment of almond pruning wounds. Comparisons of different application timings of BCA in relation to pathogen inoculations revealed a significant improvement in wound protection when inoculations were conducted 7d versus 24h post BCA application for N. parvum, but not for E. lata. Trichoderma atroviride SC1 and T. paratroviride RTFT014 are promising candidates for the preventive protection of almond pruning wounds and for inclusion in integrated pest management programs and organic almond production systems.