Fungicide sensitivity of Colletotrichum isolates and efficacy in controlling persimmon anthracnose

To control persimmon anthracnose, fungicides are applied from flowering until fruit harvest. Systemic fungicides registered for this crop are mainly from the group of quinone outside inhibitors (QoIs) and demethylation inhibitors (DMIs), both presenting risks for resistance development. For this reason, sensitivity studies and fungicide efficacy tests are important to determine the levels of sensitivity of isolates from different Colletotrichum spp. from persimmon to fungicides. The objectives of this work were: (i) to investigate the sensitivity of Colletotrichum isolates obtained from persimmon twigs and flowers to registered and non-registered active ingredients; (ii) to evaluate the cross-resistance of Colletotrichum spp. among tested fungicide groups; and (iii) to test the efficacy of fungicides in controlling anthracnose on immature and mature detached fruit. There were differences between Colletotrichum spp. in levels of sensitivity to the active ingredients evaluated, with C. horii isolates being more sensitive to site-specific fungicides than C. chrysophilum , C. nymphaeae and C. melonis . There was a high risk of cross-resistance for the active ingredients of the QoIs, medium risk for the DMIs and multisite compounds, and low risk for the succinate dehydrogenase inhibitors (SDHIs). Negative cross-resistance correlation was observed for anilopyrimidines (APs). Anthracnose control in immature and mature fruit ex vivo varied between products. In general, isolates recovered from both twigs and flowers were sensitive to the fungicides tested. The SDHI fungicides were efficient in controlling Colletotrichum in the in vitro assay, appearing as an alternative to be tested in the control of the disease. Difenoconazole-based fungicides and mixed formulations of QoI and DMI were the most effective for controlling persimmon anthracnose both for immature and mature fruit.