APS Homepage

Poster: Biology & Disease Mgmt: Chemical Control


Monitoring Colletotrichum acutatum Resistance to Quinone-outside Inhibitor Fungicides in Strawberry
B. FORCELINI (1), B. Forcelini (1), N. Peres (1) (1) University of Florida, U.S.A.

Colletotrichum acutatum, the causal agent of anthracnose fruit rot (AFR) and anthracnose root necrosis (ARN), is a major fungal pathogen affecting strawberry. Control of AFR and ARN has been dependent on the use of Quinone-outside Inhibitor (QoI) fungicides. Resistance of C. acutatum isolates to QoI fungicides was reported for the first time in 2013 in Florida, and was linked to five specific strawberry nurseries from Canada and North Carolina. In 2016, C. acutatum isolates were collected after outbreaks of ARN in Florida and coastal California. Ninety isolates from four nurseries were tested for QoI sensitivity using a discriminatory dose mycelial growth assay. Forty-two isolates were not inhibited at 3 nor at 100 µg azoxystrobin per ml and were considered QoI-resistant. Resistant isolates originated from two of the four nurseries tested. C. acutatum resistance to QoI fungicides is becoming a widespread problem in strawberry nurseries located in different regions. This situation warrants immediate changes in anthracnose management strategies that integrate non-chemical strategies to limit selection and prevent spread of QoI-resistant populations.