Examining Resistance to DMI Fungicides: Anti-resistance strategies

Dollar spot disease on Kentucky bluegrass (left) and creeping bentgrass (right). Photo courtesy Tom Hsiang

By Tom Hsiang, PhD

A case study on the development of DMI fungicide resistance illustrates some of the conditions that may lead to disease control failure. At a golf course outside of Chicago, where resistant isolates were found, an older variety of creeping bentgrass was used that was very susceptible to dollar spot. This likely led to greater frequency of fungicide use. Secondly, nitrogen levels were purposely kept low to prevent the occurrence of other diseases, such as Pythium blight, which again may have contributed to greater fungicide use because dollar spot disease is favoured by low-nitrogen regimes. Thirdly, DMI fungicides were used extensively for several years.

General recommendations to prevent DMI resistance problems in fungi include:
● not using repeated applications of DMI alone;
● using mixtures or alternating with non-DMI fungicides;
● reserving DMI use for the critical part of the season;
● using label rates rather than reduced doses; and
● using other measures such as resistant varieties and cultural practices.

Read the full article: Examining Resistance to DMI Fungicides

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