The Potassium Phosphite-Based Fungicide Canon® Controls Basil Downy Mildew Under Greenhouse Conditions in Israel

Sweet basil downy mildew (BDM), caused by Peronospora belbahrii is the most destructive disease of commercially produced sweet basil in Israel and unless properly managed, may lead to 100% yield reduction. Four experiments were conducted over three growing seasons (fall 2021, fall 2022 and spring 2023) under commercial-like conditions to determine the efficacy of the phosphonic acid-based fungicide Canon ® following a conservative, seven-day protective spraying protocol. While Canon did not eradicate the pathogen, treated plants had 41 to 99.9% less (P<0.05) disease incidence and / or severity than the untreated control plants. The disease scores on plants treated with Canon were similar (P>0.05) to an alternation of Revus ® / Cabrio ® in fall 2021; less (P<0.05) than Revus in fall 2022 and higher (P<0.05) than an alternation of Acrobat ® / Cabrio at the end of the spring 2023 experiment. The inhibitory effect of Canon, its short pre-harvest application interval and low cost compared to other fungicides make it an excellent addition and a potential replacement for controlling BDM under greenhouse conditions that should be further explored.