As instances of resistance to multiple herbicides continue to rise, it is important that growers have the information needed to respond quickly. They need to understand which weeds are resistant to which herbicides and the strength of that resistance.

Unfortunately, though, the greenhouse screenings and population studies typically used for resistance analysis are time consuming and labor intensive – impeding a rapid response.

A team of scientists writing in the journal Weed Science say a new “leaf-disk assay” may be the answer. The test uses chlorophyll fluorescence emissions to determine whether a weed is resistant to various systemic or contact herbicides. Results are available in about 48 hours.

In a recent research study, scientists were able to use the fluorescence technique to detect resistance to glyphosate, dicamba and fomesafen in broadleaf and grass weeds, including Palmer amaranth, waterhemp, kochia and goosegrass.

The team says further work is needed to fine-tune the test for greater precision among plants with lower levels of resistance. But they are confident that the assay holds great promise. In addition to detection speed, an assay-based analysis requires fewer technical skills than traditional screenings and studies. That means more weed science labs should be able to identify multiple resistances and do it efficiently.

Want to learn more? Read the article “A nondestructive leaf-disk assay for rapid diagnosis of weed resistance to multiple herbicides”, which appears in Weed Science, and is available free for a month.

Photo of goosegrass, courtesy of Shutterstock.