Resistance to Boscalid, Fluopyram and Fluxapyroxad in from Michigan (U.S.A.): Molecular Characterization and Assessment of Practical Resistance in Commercial Cherry Orchards.

Management of cherry leaf spot disease, caused by the fungus , with succinate dehydrogenase inhibitor (SDHI) fungicides has been ongoing in Michigan tart cherry orchards for the past 17 years. After boscalid-resistant were first isolated from commercial orchards in 2010, premixes of SDHI fungicides fluopyram or fluxapyroxad with a quinone outside inhibitor were registered in 2012. Here, we report widespread resistance to fluopyram (Fluo), fluxapyroxad (Flux), and boscalid (Bosc) in commercial orchard populations of in Michigan from surveys conducted between 2016 and 2019.

A Method for the Examination of SDHI Fungicide Resistance Mechanisms in Phytopathogenic Fungi Using a Heterologous Expression System in .

Succinate dehydrogenase inhibitors (SDHIs) are a class of broad-spectrum fungicides used for management of diseases caused by phytopathogenic fungi. In many cases, reduced sensitivity to SDHI fungicides has been correlated with point mutations in the and target genes that encode components of the succinate dehydrogenase complex. However, the genetic basis of SDHI fungicide resistance mechanisms has been functionally characterized in very few fungi.

Survey and Genetic Analysis of Demethylation Inhibitor Fungicide Resistance in From Michigan Orchards.

Resistance to sterol demethylation inhibitor (DMI) fungicides in , causal agent of brown rot of stone fruit, has been reported in the southeastern and eastern United States and in Brazil. DMI resistance of some isolates, in particular those recovered from the southeastern United States, is associated with a sequence element termed "Mona" that causes overexpression of the cytochrome demethylase target gene . In this study, we conducted statewide surveys of Michigan stone fruit orchards from 2009 to 2011 and in 2019, and we determined the sensitivity to propiconazole of a total of 813 isolates of .

Draft Genome Sequence Resource for , the Cherry Leaf Spot Pathogen.

is the causal agent of cherry leaf spot (CLS), the most important disease of tart cherry in the Midwestern United States. Infection of leaves by leads to premature defoliation, which places trees at heightened risk of winter injury and death. Current management of CLS relies primarily on the application of three important fungicide classes, quinone outside inhibitors, sterol demethylation inhibitors, and succinate dehydrogenase inhibitors.

Boscalid Resistance in : Distribution, Effect on Field Efficacy, and Molecular Characterization.

Cherry leaf spot (CLS), caused by the fungus , is a major disease of tart cherry ( L.) trees, leading to early defoliation that results in uneven ripening and poor fruit quality in the current season, reduced fruit set in the following season, and increased potential for winter injury and tree death. Pristine (BASF Corporation, Research Triangle Park, NC), a commonly used fungicide for CLS management in Michigan, is a premix of boscalid, a succinate dehydrogenase inhibitor, and pyraclostrobin, a quinone outside inhibitor.

Evaluation of dodine, fluopyram and penthiopyrad for the management of leaf spot and powdery mildew of tart cherry, and fungicide sensitivity screening of Michigan populations of Blumeriella jaapii.

Background: Field trials were conducted on the tart cherry cultivar Montmorency to evaluate the efficacy of dodine and the succinate dehydrogenase inhibitor (SDHI) fungicides fluopyram and penthiopyrad for control of cherry leaf spot (CLS) and powdery mildew (PM). The in vitro sensitivity of Blumeriella jaapii (CLS) to the same fungicides was also tested.

Results: Treatments with dodine or fluopyram were among the most effective for controlling CLS, while fluopyram or penthiopyrad treatments were among the most effective for controlling PM.

Occurrence of QoI Resistance and Detection of the G143A Mutation in Michigan Populations of Venturia inaequalis.

Control strategies for Venturia inaequalis rely heavily on chemical fungicides. Single-site fungicides such as the quinone-outside inhibitors (QoI) have been used in Michigan apple orchards for more than 11 years. In 2008, we sampled eight commercial orchards in the Fruit Ridge growing region of Michigan in which apple scab control failures were observed on 'McIntosh' apple following applications of kresoxim-methyl or trifloxystrobin.

Occurrence, Distribution, and Polymerase Chain Reaction-Based Detection of Resistance to Sterol Demethylation Inhibitor Fungicides in Populations of Blumeriella jaapii in Michigan.

ABSTRACT The intensive use of site-specific fungicides in agricultural production provides a potent selective mechanism for increasing the frequency of fungicide-resistant isolates in pathogen populations. Practical resistance occurs when the frequency and levels of resistance are great enough to limit the effectiveness of disease control in the field. Cherry leaf spot (CLS), caused by the fungus Blumeriella jaapii, is a major disease of cherry trees in the Great Lakes region.

Integration of Copper-Based and Reduced-Risk Fungicides for Control of Blumeriella jaapii on Sour Cherry.

Practical resistance to sterol demethylation inhibitor (DMI) fungicides among populations of Blumeriella jaapii, the cherry leaf spot (CLS) pathogen, was documented in 2005. In the present study, strategies to reduce selection for DMI-resistant strains of B. jaapii and adapt to possible restrictions on the use of chlorothalonil are described.

Overexpression of the 14alpha-demethylase target gene (CYP51) mediates fungicide resistance in Blumeriella jaapii.

Sterol demethylation inhibitor (DMI) fungicides are widely used to control fungi pathogenic to humans and plants. Resistance to DMIs is mediated either through alterations in the structure of the target enzyme CYP51 (encoding 14alpha-demethylase), through increased expression of the CYP51 gene, or through increased expression of efflux pumps. We found that CYP51 expression in DMI-resistant (DMI(R)) isolates of the cherry leaf spot pathogen Blumeriella jaapii was increased 5- to 12-fold compared to that in DMI-sensitive (DMI(S)) isolates.