The cotton plants, which were sprayed with different rates of glufosinate back in June, had grown out of the damage by the time the early August field day was held. Still attendees to the field day had little trouble telling which rows were Widestrike-containing Phytogen 375 and which were LibertyLink 1773, because of the number of dead leaves in the plot rows.

When researchers waited until the nine leaf stage to apply glufosinate, there was less visible damage. “At this growth stage coverage is an issue,” Jones explains. “If you don’t get good coverage, you don’t get good weed control. Likewise, you don’t get as much plant damage,” he notes.

Jones contends any time there is a loss of leaves on a cotton plant, there is a higher risk of reducing boll fill and thus reducing yield. The cotton plant usually compensates for the leaf loss, but any number of factors can prevent the cotton plant from making this compensation, Jones explains.

“To show visitors to the field day what the June damage looked like, we sprayed the two varieties with a high rate of glufosinate in late July, with temperatures at or near 100 degrees F. We actually knocked some bolls off of the Widestrike varieties.”

“If a grower used glufosinate in a late-season salvage treatment on Widestrike cotton, I think there could be significant yield loss, Jones says.

While the practice of using Liberty Link herbicide on Widestrike cotton varieties is legal, the combination of the high value of cotton and the lack of a corporate safety net if something goes wrong, make it a high risk strategy that could cost, rather than save, growers money.

rroberson@farmpress.com