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POSTERS: Chemical control

Etiology, biology and management of almond trunk and scaffold canker diseases in California
Leslie Holland - University of California. Florent Trouillas- University of California, Kearney, Renaud Travadon- University of California, Maria Crespo- Kearney Ag. Center, Daniel Lawrence- University of California, Mohamed Nouri- Department of Plant Pathology, UC Kearney Ag. Research and Extensi

Canker diseases are the main cause of tree mortality in almond orchards in California. Pruning wounds serve as the primary infection court for fungal pathogens. Protection of wounds using fungicides and sealers has been broadly employed to control canker diseases of woody crops. The aims of this study were to identify the principal fungal pathogens associated with almond trunk and scaffold canker diseases (TSCD), assess pathogenicity, and investigate management strategies through understanding of pruning wound susceptibility and pruning wound protectant efficacy. From 2015–2018 over 120 almond orchards with TSCD were surveyed. Isolations revealed numerous fungal species associated with cankers including Botryosphaeriaceae spp., Ceratocystis destructans, Cytospora spp., Diaporthe spp., Diatrypaceae spp., and Collophorina spp. Cankers caused by Botryosphaeriaceae spp. and C. destructans were the most prevalent in California. Field trials were conducted to evaluate pruning wound susceptibility according to the month of pruning. Fungi were inoculated on pruning wounds made between September and January and varying in age from 0- to 8-weeks-old. In the pruning wound protection trials, twenty-six products were tested against eight canker-causing fungi. Results show that pruning wound susceptibility was lowest for January pruning. Susceptibility of wounds decreased after two weeks following pruning. Thiophanate-methyl and a Trichoderma biocontrol agent were the most efficacious products for protection of pruning wounds against the various canker pathogens.