Predicting herbicide resistance in noxious weeds

Photo Credit

Courtesy Photo from the Natural Resources Conservation Service

A landowner sprays to control weeds along windbreak near Belgrade, MT. 

Noxious weeds are designated plant species in the United States that cause damage to crops, livestock, poultry or other resources. Therefore, managers often seek methods, such as herbicide, to control these species.

Herbicides have been used since the 1940s to reduce and control undesirable weed populations in agricultural, rangeland, and forest systems. However, repeated herbicide use can enable herbicide-resistant populations to develop.

Predicting which species are most likely to evolve herbicide resistance and which conditions support this evolution is critical knowledge for managers. Determining which plant traits are associated with herbicide resistance can assist managers in identifying species with the potential to develop herbicide resistance and allow us to identify species that are most likely to become herbicide resistant.

To examine plant characteristics that potentially contribute to herbicide resistance, we modeled herbicide resistance of 283 noxious weed species as a function of ten biological and ecological plant characteristics. Using model results, we created a ranked assessment of the risk that current, non-resistant noxious weed species may become resistant in the future. 

We found that species with persistent seed banks and with short life spans, such as annuals, that occurred outside of riparian or wetland areas were most likely to develop herbicide resistance. In 2022, 47 of the noxious weed species analyzed in this study are herbicide resistant and our models identified an additional 63 species with traits that that would be conducive to becoming herbicide resistant.