Austrailians Confirm Roundup-Resistant Brome Grass

Australian weed scientists have confirmed a population of Roundup-resistant great brome grass in the state of South Australia.

"This is the first time that this highly competitive annual grass weed of crops and pastures has evolved resistance to glyphosate and is the third Australian weed species confirmed as resistant to glyphosate in the past 12 months," according to an announcement from the country's Grains Research and Development Corporation. "

The resistant brome grass was found surviving in a pasture where an old fence had been removed and cropped over and a pre-sowing application of glyphosate had been applied. The fence line had previously been sprayed with glyphosate for many years with no other weed control tactics used."

Brome grass test samples in 
Australia after Roundup applications. 
Photo Australian Grain Research 
and Development Corporation.

"This is a huge concern to Australian grain growers because this highly competitive weed has been becoming a major problem in reduced-tillage farming," said Associate Professor Chris Preston, chair of the Australian Glyphosate Sustainability Working Group and leader of the University of Adelaide team which confirmed the result. "Currently, the number of glyphosate-resistant ryegrass populations evolving along fence lines is exploding. That and this new discovery are a real 'wake-up call’ and show that any weed might develop glyphosate resistance and growers need to be vigilant."

Brome grass is a major weed of crop and pasture on lighter textured soils across the southern and western Australian cereal belts. In wheat, there are few effective in-crop herbicide options for this species, and it can reduce yields by 30 to 40%. It also emerges after crop establishment enabling it to compete strongly with the crop and produce large amounts of seed.

Brome grass is also a host to a range of cereal crop diseases including take-all and barley net-blotch, while the mature seeds can injure stock. Populations of brome grass are already resistant to grass selective Group A and Group B herbicides in Victoria and Group B and Group C herbicides in Western Australia.

Preston knows that managing brome grass and other weeds along fence lines requires a diverse approach. Herbicides with different modes-of-action to glyphosate need to be included. On erosion-prone sites ground cover needs to be maintained so control along fences and firebreaks should take place late winter to early spring. The older tactic of sowing crops to the fence line then baling and spraying an area along the edge of the crop for a firebreak is a valuable way of stopping weeds moving into the crop while protecting the soil.

Tankmix Options And Approaches When Dealing With Roundup-Resistant Weeds

Roundup resistance has made tankmix strategies more important than ever for growers who either want to delay its onset or deal with problems that already have developed.

Here's an article from DTN/Progress Farmer that covers resources, like apps and on-line videos, that cover proper tankmix procedures.

Roundup Resistance Management And Weed Control In Cotton And Grains Covered In Video Series

The National Cotton Council has created a series of short educational videos on weed resistance management and control strategies in cases where weed resistance has developed.

The videos cover cotton but also relate closely to the same issues in corn and soybeans. The programs include commentary from a number of Southern weed scientists involved with Roundup-resistant Palmer pigweed, horseweed - marestail and other weed pests that have gained varying degrees of resistance to Roundup and other glyphosate products.

The Weed Resistance Video includes interviews with four cotton producers who have firsthand experience with weed resistance. They discuss why this concern must not be ignored and provide valuable information on how to deal with weed resistance.

Other videos include:

• Biology and Management of Pigweed
• Field Day with the University of Georgia's Stanley Culpepper
• Horseweed: Control this Weed Early
• Field Day with University of Tennessee's Larry Steckel
• Corn Weed Management
• Weed Resistance Management

Roundup-Resistant Pigweed And Johnsongrass Now A Reality In Louisiana

Until just the last year or so, Louisiana has mostly dodged the bullet when it came to Roundup-resistant weeds, especially two severe problems: resistant pigweed and resistant johnsongrass.

But events caught up with the state, and Louisiana State University weed scientists have been confirming more cases of known resistance.

Don't Get Behind With Roundup-Resistant Pigweed, Says Arkansas Farmer

From February's National Conservation Cotton and Rice Conference in Baton Rouge, Louisiana:

Wayne Wiggins, of Arkansas, said herbicide-resistant pigweed appeared on his farm rapidly. “I was just stunned at how fast it came on.” He said it’s important to talk with neighbors about their weed problems and be prepared for resistance issues. 

“You’ve got a narrow window. When you get behind, you are over and done.” Wiggins said he uses atrazine on corn for its residual effects. “I’ll use a residual on all my bean fields this year.” 

He said rice is a good rotation crop to address pigweed, but the weed must be controlled on levees.

Source: Bruce Schultz, LSU Ag Center

Hooded Sprayer From Wilmar Aimed Directly At Roundup-Resistant Weed Control

Hooded sprayers were left to rust and rot in the weeds after Roundup Ready became the dominant weed control measure in cotton and other crops in the South.

Now, though, with the shift toward more Roundup-resistant weeds, hooded sprayers have been reentering fields, and more units are being sold.

Roundup-Resistant Ryegrass: Mississippi Schedules Symposium For March 10

Mississippi farmers are a few years into the fight against glyphosate-resistant weeds, a problem that is the focus of a March 10 field day in Stoneville.

Producers will take a close look at ways to manage herbicide resistance in the Glyphosate-Resistant Ryegrass Field Day at Mississippi State University’s Delta Research and Extension Center in Stoneville. Registration begins at 7:30 a.m. at the Capps Center, and the field day concludes with lunch. The program will move indoors if there is bad weather.

Conventional Cotton Herbicide Control: One Approach

Editor's Note: Rusty Harris, Extension Agent in Worth County, Georgia, developed the following systems approach for his farmers who want to grow cotton that lacks herbicide resistance traits:

This program should provide adequate control of palmer amaranth, ipomea morningglory species, yellow nutsedge, bristly starbur, and tropic croton.

Roundup-Resistant Pigweed Management Plan For 2011 From Georgia

R.J. Byrne, Extension Agent in Thomas County, Georgia, has produced a short video (see below) about Georgia's approach for controlling Roundup-resistant Palmer pigweed in cotton. In the video, Byrne interviews Stanley Culpepper, Georgia Extension Weed Scientist.

Here's a supplemental handout that goes into more detail about herbicides, rates and other factors touched on during the video.