UNL Extension



Herbicide-Resistant Marestail

This Can You Guess It?? Photo is featured in the January 2007 Nebline Newsletter

Pesticide-resistant Marestail

UNL researchers have confirmed the first glyphosate-resistant weed species in Nebraska — marestail, also know as horseweed. While Nebraska researchers first suspected resistance had developed almost a year ago, it took tests and growing plants from last year's seeds to confirm it.

Horseweed, also known as marestail and Canada fleabane, is native to North America. Horseweed is a problem weed in areas where crops are grown. It competes for light, water, and nutrients. Horseweed can be a host for plant pests and plant diseases.

There are three factors causing an increase of horseweed in fields: the same crops are planted in the same location year after year, the soil is tilled less, and now herbicide resistance - in particular Glyphosate-resistantance (which is sold under the trade names Roundup®, Touchdown®, and others).

Weed resistance is not new to agriculture; researchers and farmers are constantly battling the resistance plants build up to herbicides. When a farmer uses a herbicide over and over again, eventually the weeds it is supposed to kill build up a resistance to the herbicide and fewer are killed. By changing some management practices, farmers can help slow down herbicide resistance.



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