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Title: The current state of resistance to acetohydroxyacid/acetolactate synthase inhibitors

item Shaner, Dale

Submitted to: International Plant Protection Congress
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2011
Publication Date: 8/6/2011
Citation: Shaner, D.L. 2011. The current state of resistance to acetohydroxyacid/acetolactate synthase inhibitors. 2011 American Phytopathology-International Plant Protection Congress Joint Meeting. August 6-10-2011 Honolulu, HI

Interpretive Summary:

Technical Abstract: The acetohydroxyacid/acetolactate synthase (ALS) inhibiting herbicides are used for weed management in multiple crop and non-crop situations. Herbicides with this mechanism of action were introduced in the early 1980s and quickly came to dominate many cropping situations due to their broad spectrum of weed control and favorable environmental profiles. However, the use of ALS inhibitors selected for herbicide resistant weed populations within a few years after growers began to apply these herbicides over broad areas. Although ALS inhibitors are extremely effective herbicides, multiple mutations can occur at the target site, acetohydroxyacid synthase, that prevent the binding of the inhibitors but that do not seem to have a deleterious effect on the enzyme activity. Currently ALS inhibitor resistance has been selected in 107 species and in over 300 biotypes. There is more resistance to ALS inhibitors than there is to any other mechanism of action. However, ALS inhibitors are still widely used and still provide effective weed management. New herbicides that are ALS inhibitors continue to be registered, in spite of the fact that resistance can be quickly selected. The introduction of glyphosate-resistant crops slowed the selection of ALS inhibitor resistance in major crops such as maize, soybeans, cotton and canola. The selection of glyphosate resistant weed populations has resulted in the re-introduction of ALS inhibitors into weed management programs. The judicious use of ALS inhibitors in an integrated weed management program can retain the effectiveness of these herbicides while still managing resistance.