Management of Twig Canker and Shoot Blight of Almond Caused by Diaporthe amygdali: Efficacy of Chemical Fungicides and Biological Control Agents.

This study evaluated the in vitro and in planta efficacy of six chemical fungicides (boscalid, captan, copper oxychloride, difenoconazole, pyraclostrobin, and potassium hydrogen carbonate) and two biological control agents (Bacillus amyloliquefaciens subsp. plantarum D747 and Trichoderma atroviride strain SC1) against Diaporthe amygdali, the causal agent of twig canker and shoot blight disease of almond. In vitro assays demonstrated that D. amygdali is highly sensitive to captan, difenoconazole, and pyraclostrobin. Regarding biological products, dual antagonism assays showed high efficacy for T. atroviride. Subsequently, the pre- and post-infection activity of all products was assessed on one-year-old almond plants. Efficacy varied significantly depending on the timing of application. Trichoderma atroviride was effective at all application times, achieving mean percent disease control (MPDC) values of 100% when applied preventively. Pre-infection applications of difenoconazole and pyraclostrobin resulted in 100% MPDC. However, their efficacy progressively decreased when applied post-infection. Bacillus amyloliquefaciens and captan showed variable results, reaching a maximum of 73% and 87% MPDC, respectively, when applied before inoculation. In contrast, boscalid, copper oxychloride, and potassium hydrogen carbonate exhibited very low MPDC values, regardless of application timing. These findings provide valuable information for improving management strategies against D. amygdali in almond orchards.