Published on: 18:07PM Jan 26, 2010
At the recent 2010 Beltwide Cotton Conference in New Orleans, glyphosate weed resistance came up more than once. Weed scientists offered their solutions to manage against resistance.
For example, Jason Bond, Mississippi State University weed scientist, discussed glyphosate-resistant Italian ryegrass in Mississippi. Italian ryegrass is an example of a weed developing resistance in multiple cropping systems. This weed was first confirmed glyphosate-resistant in perennial crops – specifically Oregon orchards – in 2004. Although not listed on www.weedscience.org, California also has this problem. (In fact, it was mentioned at the recent state Weed Science Society Meeting.) Now confirmed in resistant in Mississippi, control problems have also been reported in Tennessee and North Carolina.
In orchards, pre-emergence and residual products are recommended for control. And the solution is similar for cotton growers. Bond recommended fall burndown programs if spring glyphosate applications fail to control Italian ryegrass. According to Bond, residual herbicides provided excellent residual control when applied in first two weeks of November. Of course, fall burndown timing has passed, but an early spring burndown may be an option. If you had a problem last year, expect a bigger problem in 2010…that’s the nature of glyphosate resistance.