2009 Year in Review

From the Fields

Herbicide-resistant weeds are an increasing concern to production agriculture. Currently in Illinois, there are biotypes or populations of 11 different weed species that are resistant to one or more families of herbicides. In 1985, common lambsquarters was the first weed in Illinois found to be resistant to herbicides (triazine family).

With the high cost of developing a new herbicide, good management practices are the best option for dealing with herbicide-resistant weeds. University of Illinois Extension weed control specialists recommend the following strategies to help deter the development of herbicide resistance.

- Scout or monitor fields regularly to identify resistant weeds. Note changes in the pest population that may indicate resistance.

- Rotate herbicides with different sites of action as crops are rotated or in continuous crops. Site of action refers to the location within the plant where the herbicide “works’.

- Apply herbicides in tank-mixed, prepackaged, or sequential mixtures that include multiple sites of action. Herbicides in the mixture must have substantial activity against potentially resistant weeds, as well as similar soil persistence.

- Do not apply a herbicide with the same site of action more than once during the growing season.

- Combine mechanical weed control practices (rotary hoeing, cultivation, etc.) with herbicides. In other words, use multiple weed control methods and don’t rely 100 percent on chemical control.

- Clean tillage and harvest equipment before moving from fields infested with resistant weeds to fields that are not infested.

Knowing the site of action of the herbicide(s) one uses is an important step in managing weed resistance. To identify herbicides by their site of action, see the four-page color factsheet titled “Herbicide Classification by Site of Action”. It can be ordered from this web site or it may be available at local University of Illinois Extension offices.

by  Editor, theCity1.com
January 30, 2009