EFFINGHAM, Ill. — Weed management has become more complex as the list of documented herbicide-resistant species continues to grow.
There are now more than 100 species of weeds with resistance to two sites of action worldwide, over 50 species resistant to three SOAs and nearly 20 species resistant to five SOAs. There also is a documented case of six-way resistance, according to the International Herbicide-Resistant Weed Database.
To help farmers sort out their options, Beck’s Practical Farm Research sites are delving deep into the weed control issue with a broad range of in-field research.
Joe Bolte, Southern Illinois PFR operator and herbicide specialist, led a tour of trials at the facility adjacent to the “Cross of the Crossroads” along Interstate 57/70.
“Everyone has to get familiar with the dos and don’t in providing effecting weed control. It’s all a learning curve and that’s why we do these demonstration plots. We want growers to be successful,” Bolte said.
“We want them to have good weed control and manage the technology properly. We know how complicated weeds are and how hard they are to control.”
The trials provide a tool to help farmers make the right decisions in weed management while keeping their eye on the bottom line.
“The last thing you want to do right now is to reapply something because you didn’t have the right spray rate, or you didn’t have the right ratio,” Bolte said.
Here are some examples of the research being done at this PFR that Bolte described.
On Pre-Emerge Products
This trial features three different application timings and how that impacts yield and influences weed control.
A pre was applied and the soybeans were planted following another application right after the planter pass. The trial also compared herbicide that was and was not incorporated into the ground.
“I look at a residual as a blanket of protection and after four weeks we start getting holes in blanket. That’s why we talk about in-season residuals and layering that next blanket down to protect that before we have holes,” Bolte said.
The planting rate in this trial was 140,000 seeds per acre. The control stand count was 137,000. The no incorporation of the pre-emerge herbicide applied 21 days before planting, as well as the incorporation, both had stand counts of about 130,000. The stand count for pre-emerge right after planting with no soil disturbance was 120,000.
“We have less of a stand there, but soybeans can compensate and branch out, so we’ll check the yield. We know that gives us our best weed control, but now we’ll see what happens with the yield impact,” Bolte said.
On Cover Crops
A new trial this year looks at the potential for using cover crops for weed control as part of an integrated pest management system.
The trial includes planting 30 pounds and 60 pounds per acre of cereal rye, broadcast versus drill, a mix of rye and rapeseed and a 60-pound per acre mix of wheat, hairy vetch and hairy vetch. The cover crops were planted the end of October and the soybeans were planted into green this spring.
The trials also looked at termination ranging from using a pre 21 days before planting to terminating at planting.
The testing opens up a lot of possibilities in terms of another weed control tool.
“This is our first year of this trial. We still have a lot to learn. I think next year we can potentially do more work with cover crops. This was to kind of get our feet wet and see if the growers are interested in it,” Bolte said.
“The cover crops did an awesome job. This is maybe a way to take some of the pressure where we don’t have to rely so heavily on certain products and still have effective weed control.
“We know cover crops did help. As heavy as the waterhemp pressure is on this farm, and the only thing we did is cover crop and one residual and Roundup. What this tells me is if we maybe did an in-season residual or kind of change our timing maybe would have had better luck, but it shows me we’re really close to having an awesome program. That encapsulated acetochlor in Warrant is helping us out where we have a lot of biomass.”
On Canopy Closure
Numerous university trials confirm that canopy closure helps weed control, providing another to help take the pressure off of herbicides.
“We wanted to look at how the pre-emerge herbicide influences canopy closure. When we reach canopy closure and we don’t have weeds underneath that canopy, we won,” Bolte said.
“Mother Nature throws us a lot of curveballs to get to that point. For instance, this year we were so cool and wet in May that the soybeans didn’t get a lot of growth. So, that put more pressure on the pre-emerge herbicides because we essentially rely on canopy closure. That pre is only going to last 4 to 5 weeks and we’re hoping that we get canopy closure. When we spray an in-season overlapping residual with our post trip, that buys us another 4 weeks, which likely gets us to canopy closure.”
The trials include row widths of 7.5 inches, 15 inches and 30 inches and also look at populations of 100,000 and 150,000, as well as 100,000, 150,000 and 200,000 in the 15-inch rows.
“The first study of various row widths has three effective sites of action. The next 40 feet of trials has one effective site of action and has waterhemp pressure. This shows that if we don’t have canopy closure we probably can’t get away with one effective site of action. In the narrower rows, you don’t see as much waterhemp. It shows that canopy closure makes a big difference,” Bolte explained.
Other trials include looking at Enlist system’s herbicide options, the interaction between herbicides mixes and how certain mixes and rates can cause antagonism.
On ‘Pre’ Power
“The power is in the pre. An ounce of prevention is worth a pound of cure. If we never let the weed emerge, it’s going to be a lot easier to control and we’re going to be a lot more successful in that post trip. The more layers of residual we have, or the more power in the pre we have, the better the weed control,” Bolte said.
“This is the second year for the small plot weed management demonstrations. A lot of what we saw last year, we’re seeing this year. This year, we’ve focused more on fine-tuning carrier rates and things along those lines.
“Last year was more of just trying to understand the different mixtures. We’ve done less of that this year and more fine-tuning what carrier rate, what weed size.
Results of this year’s trials and will be featured in Beck’s comprehensive PFR book. A video of the demonstration plots will also be available, as well as one-page sheets with information on the various herbicide technologies available.