• Phytogen and Dow AgriSciences do not recommend or warrant use of glufosinate herbicides on Widestrike cotton and all risk of crop damage or loss associate with this practice is the responsibility of the grower.

Clemson University Cotton Specialist Mike Jones conducted a series of tests in the 2011 cropping season to determine the amount of damage from applying varying rates of glufosinate on Widestrike cotton.

Speaking at a recent field day, Jones stressed that Dow and Phytogen do not recommend this practice and, therefore, neither does Clemson University — or any other university.

In his research project at the PeeDee Agriculture Research and Extension Center near Florence, S.C., Jones looked at one-time applications of 29, 58, 87 and 116 ounces per acre of glufosinate on Widestrike cotton.

He notes that it is legal to apply up to 87 ounces of glufosinate on cotton during one growing season.

LibertyLink 1773, which is tolerant to glufosinate, was planted in side-by-side plots next to Phytogen 375 cotton, which contains the Widestrike gene. The cotton in this test was planted on May 16, in 40-foot long plots.

Glufosinate was sprayed on the plots at the three leaf stage, at various rates, at the nine leaf stage at varying rates and at both the three and nine leaf stage at various rates.

“Even at the lower rates we did see an interaction between varieties,” Jones says.  “That’s exactly what Dow and Phytogen predicted would happen,” he adds

The Clemson researchers used a 0-10 rating scale to measure overall plant health in the plots. Across all treatments there was more damage in the Widestrike plots than in the LibertyLink varieties, he points out.

How much the leaf loss and plant discoloration affects yield loss and cotton quality will be determined when the cotton plots are harvested.

In similar tests at the University of Georgia, researchers saw consistent 15-20 percent leaf loss, but there was no corresponding loss of yield.