University weed scientists and Extension farm agents across the Cotton Belt are making a concerted effort to help growers understand the threat of herbicide resistant weeds and to help them make good management decisions that will extend the life of new technology and improve crop profitability.

There has been much written about the use of glufosinate, arguably the next best thing to glyphosate because of glyphosate resistance problems with Palmer pigweed and other weeds.

Though the most ‘in-the-news’, glyphosate is not the only herbicide with resistance issues. Several families of herbicides share the plight of glyphosate.

New chemistries, whether herbicides, fungicides or insecticides, all strive to delay or prevent seemingly inevitable resistance problems associated with over-use or miss-use.

The LibertyLink system is one of these technologies.

FiberMax and Stoneville LibertyLink cottonseed varieties, LibertyLink soybean varieties, multiple corn brands and InVigor LibertyLink canola contain the LibertyLink trait, which confers full tolerance to Liberty herbicide, or glufosinate.

Long-time North Carolina Weed Scientist Alan York says bluntly that there are no more silver bullets for weed control, especially for control of Palmer amaranth.

Glufosinate is the best next herbicide growers have, and they need to use it wisely to prevent a similar scenario that we now see with glyphosate resistant weeds, York says.

For several years a number of cotton growers in the Upper Southeast have used glufosinate on Phytogen brand cotton that contains a Widestrike gene and a marker gene similar to the resistant gene used in LibertyLink cotton varieties.

Phytogen Widestrike varieties do not have the LibertyLink trait, which is what confers tolerance to full labeled rates of glufosinate.

In some cases, best management practices are compromised in order to avoid injury to the crop.

When growers use glufosinate on Phytogen Widestrike cotton, they have to pay special attention to timing of application — even down to what time of the day it is sprayed on cotton plants.

They also risk damage to the cotton crop, and they often reduce the rate to reduce the risk of damaging their crop.