Weed Research Highlights Issues

Herbicide Update: We are currently working with one totally new herbicide in rice: Grasp, from Dow Agrosciences. It is somewhat like Regiment in that it is strong on barnyardgrass and several broadleaf weeds while being weaker on sprangletop. Grasp provided very good control of barnyardgrass in Delta Center research. BASF has obtained registration for a new mix product called "Clearpath". Clearpath is a package mix of Facet and Newpath (or Pursuit) for Clearfield Rice. We are continuing to evaluate Beyond in Clearfield rice for salvage purposes. We are also evaluating Beyond as a "no-carryover" replacement for Newpath. However, at this time, the rotational safety of Beyond in a rice system is unknown. Syngenta continues to offer new corn herbicides based on mixes with Callisto- Lumax and Lexar both contain Callisto, atrazine and Dual. The Lexar herbicide contains higher atrazine rates and is intended for Southern environments.

Roundup Ready Flex Cotton: This is our second year to work with Monsanto's Roundup Ready Flex Cotton (cotton that does not have the 4-leaf, over-the-top cutoff). Many growers ask what the application cutoff is. Monsanto has not set an over-the-top cutoff; however, it will be late enough that it should not be of any practical significance. The utility of the Flex cotton became clear in 2004. It was rainy when our post-direct treatments should have been applied and we lost our height differential and cotton reached the 6-leaf stage. Being able to spray just once more, over-the-top, would have solved this problem. In most fields, we think the Flex cotton will be managed more or less like Regular Roundup Ready. A few growers will make an extra over-the-top application, however existing Roundup Ready programs provide excellent weed management. Traditional layby treatments (Direx + MSMA or any of a number of alternative herbicides), help both programs since glyphosate has no residual activity. The added modes of action are also important for the sake of resistance prevention. Residual layby treatments will be the simplest, most economical way to "finish" a flex program.

Scouring Rush. Have you noticed a strange, dark green, "cane-looking", hollow weed creeping out of your ditches into your fields? This weed is called scouring rush. We have been researching control methods for the last two years and have had more failures than successes. Gallon rates of Roundup had virtually no effect on the weed. Full rates of Hyvar have provided less than 50% control. The active ingredients 2,4-D and triclopyr have given us 50 to 75% control when applied together; however, this control has not been permanent. The herbicide Crossbow is a premix of 2,4-D and triclopyr. One positive note is that rush seems to be linked to drainage ditches and does not spread any further than 20-feet out into a field.