Are there concerns regarding development of resistance to fungicides among the ASR population?
Triazoles and strobilurins are among the fungicide classes registered for use on soybean to control ASR. There is a risk of resistance development with triazoles and, particularly, strobilurins. To ensure that these fungicides retain their activity against soybean rust, adhere to the following guidelines: • Limit solo applications (e.g. applying only a strobilurin or only a triazole fungicide). When a single fungicide class is used, apply only one strobilurin or two triazoles per growing season. • Do not apply consecutive solo applications of fungicides in the same class. Instead, alternate fungicide classes during the season (e.g. follow a strobilurin spray with a triazole spray, or vice-versa). • Use the rate recommended on the label. • Use a premixed fungicide product, containing both a strobilurin and a triazole. This allows more than a single mode of activity against ASR and decreases the likelihood of resistance development. Finally, growers should monitor fields after fungicide
