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Angie Peltier

Angie Peltier
Former Extension Educator, Commercial Agriculture

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Hill and Furrow

Current topics about crop production in Western Illinois, including field crops research at the NWIARDC in Monmouth.
Figure. Growth regulator injury on cucumber.
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Communication is key when it comes to growth regulator herbicides

Posted by Angie Peltier - Weeds

Growth regulator herbicides (GRH)

Hormones (plant or animal) are chemicals that at very low concentrations regulate the activity of certain cells, tissues or organs. Auxin is a naturally occurring plant hormone and works in concert with other plant hormones to affect many different plant processes including: which type of plant cells will grow, how much these cells will grow, and in what direction. Growth regulator herbicides are also known as synthetic auxins.

Very low concentrations of auxins occur naturally in plants. This fact has been exploited in the development of synthetic auxins as herbicides for broad-leaf weed control. Unfortunately, in certain situations, these herbicides have been known to cause injury to sensitive, non-target plants (Figures).

In recent years, seed and chemical companies have been working through the US-EPA regulatory process to gain approval for the release of soybean varieties that, through genetic modification, are tolerant to the synthetic auxins dicamba (Monsanto) or 2,4-D (Dow AgroSciences). These companies are working to minimize off-target plant injury through the development of lower-volatility herbicide formulations, educational programs, and specific label requirements.

Perspectives on GRH may differ

Conventional soybean producers may be excited about the prospect of a new herbicide to add to their in-season weed control tool box, particularly those battling weeds that are resistant to other herbicides.

It is, however, important to keep in mind that not every Illinois citizen may be excited about this new technology. In visiting with Extension colleagues that serve clientele other than conventional corn and soybean producers (large- and small-scale producers of conventional or organic fruits, vegetables, and ornamental plants) there is quite a bit of uncertainty and apprehension about the release of this technology.

New online PSEP course

An online course, "Herbicide Tolerant Crop Stewardship" was recently developed by personnel in the University of Illinois Pesticide Safety Education Program (PSEP). This course focuses on good stewardship of growth regulator herbicides including strategies to minimize both particle and vapor drift and off-target plant injury. A portion of this course also addresses how important it is to keep open the lines of communication between neighbors. It might not be a bad idea to spend a little bit of time refreshing our knowledge about general GRH stewardship before the release of GRH-tolerant soybean varieties.

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