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Confirmed Report of Fungicide Resistance in the FIELD PEA Ascochyta/Mycosphaerella Blight Pathogen (06/21/18)

Resistance to the QoI fungicides (FRAC group 11) has been confirmed in the pathogen that causes Ascochyta / Mycosphaerella blight in FIELD PEA.

Confirmed Report of Fungicide Resistance in the FIELD PEA Ascochyta/Mycosphaerella Blight Pathogen

Resistance to the QoI fungicides (FRAC group 11) has been confirmed in the pathogen that causes Ascochyta / Mycosphaerella blight in FIELD PEA. To be clear, this should be considered only a first report of resistance. We currently do not know how widespread this resistance is. However, if growers apply any FRAC 11 fungicides on field pea this growing season for Ascochyta/Mycosphaerella blight (such as Headline, Quadris) or premixes containing FRAC 11 fungicides, it is important to monitor fields for management of the disease.

The identification of the fungicide resistant pathogen was confirmed several ways. First, reduced control of FRAC 11 fungicides was observed in a fungicide trial on field’s peas at the Carrington Research Extension Center.  Isolates of the suspicious pathogen were sent to Dr. Pasche’s pulse crop and dry bean laboratory at NDSU. The pathogen isolates were grown in petri plates on agar (growth media) that contained different levels of FRAC 11 fungicides. The fungicide resistant isolates were able to grow on agar that contained levels of fungicide 50 to >1,000 higher than the control isolates. Thus, confirming a sensitivity shift (thus, ‘resistance’) in the laboratory.

Next, field pea plants were grown in the greenhouse and infected with the pathogen. When the control pathogen was used, the FRAC 11 fungicides controlled the disease. However, when the fungicide resistant isolates were used, the disease was not controlled. In the photo below, the fungicide resistant isolate was used to infect the field peas. From Left to Right, the plants were the control treatment (sprayed with only water), sprayed with headline (a FRAC 11 fungicide), and sprayed with Proline (a FRAC 3 fungicide).

markell

To determine how widespread the resistance is, we will actively be conducting a pathogen survey this summer. This will be critical knowledge for the development of management recommendations in the future. Without this knowledge, it is premature to make widespread changes to management recommendations. However, as stated before, it is very important that growers closely monitor fields for Ascochyta / Mycosphaerella blight after applying FRAC 11 fungicides to field peas.

To be clear, this information only applies to FRAC 11 fungicides, and only to the pathogen that causes ascochyta blight on field peas. The pathogen that causes ascochyta blight on chickpeas has been known to be resistant to FRAC 11 fungicides for over a decade. To the best of our knowledge, the pathogen that causes ascochyta blight on lentils is still sensitive to FRAC 11 fungicides (thus, Headline, Quadris, etc... are still effective).

 

Sam Markell

Extension Plant Pathologist, Broad-leaf Crops

 

Julie Pasche

Research Plant Pathologist

NDSU Dept. of Plant Pathology

 

Michael Wunsch

Research and Extension Pathologist

NDSU Carrington REC

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