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POSTERS: Fungicide and antibiotic resistance

Monitoring Fungicide Resistance in Botrytis cinerea on grapes in Michigan
Safa Alzohairy - Michigan State University. Chang-Lin Xiao- USDA ARS, Rachel Naegele- USDA ARS, Seiya Saito- USDA ARS, Jerri Gillett- Michigan State University, Timothy Miles- Michigan State University

Botrytis cinerea is an important pathogen on small fruits worldwide. On grapes, it causes bunch rot at both pre- and post-harvest stages, where losses can reach up to 100%. Chemical control primarily relies on the prophylactic use of synthetic site-specific fungicides. Repeated applications of these products raise the risk of fungicide resistance development in B. cinerea populations, resulting in crop management failures. To determine the extent of resistance, B. cinerea isolates were collected from grape clusters in the northwest and southwest grape growing regions of Michigan in 2014 (n = 115) and 2018 (n = 125). These isolates were phenotyped using discriminatory doses of 8 fungicides to determine the levels of resistance. Fungicide resistance increased from 2014 to 2018 with a higher increase in fenhexamid, fluopyram, and iprodione resistance. B. cinerea isolates resistant to multiple fungicides were detected in 2014 and 2018 with a higher frequency being observed in 2018. Our data provide essential information to growers about the efficacy for B. cinerea control using the available botryticides. Future work will develop molecular markers for resistance that can be used for early fungicide resistance detection in the field and in fungicide stewardship programs. The developed markers will be transferred to diagnostic clinics to assist growers in the management of bunch rots before resistance related control failures occur.