Creating the perfect weed control program is a strategy, says Dean Mosdell, technical manager for Syngenta.
“Just simply seeing a weed grow in a lawn and picking a post-emergent product is probably short term,” he says. “But for a long-term strategy, think about what the turf is, what weeds are present and how you can control them.”
A pre-emergent herbicide is important in preventing the weeds, but it’s equally important to have a post-emergent plan to control the ones that pop up.
“Post-emergents represent a curative approach instead of a preventative approach,” says George Furrer, director of specialty business for SipcamAdvan. “You can have a sound, preventative program and still require some curative products or post-emergent products.”
Furrer says some companies choose to forgo the preventative approach to weed control and instead focus on curative, but even companies that have a strong preventative program will still need to come back later in the season and touch up.
Jason Fausey, director of technical services, turf and ornamentals with Nufarm, says a sound weed program needs both pre- and post-control to be effective.
“We can’t control the weather, so it becomes difficult to expect perfect weed control,” he says. “(Pre-emergents are) a perfect foundation, but you always expect to see breakthrough and that’s where our post-emergent aspects come from.”
Making a choice.
Picking the right post-emergent requires a knowledge of what you want to treat and how you want to apply it.
First, you need to decide liquid versus granular. Jim Goodrich, a product manager with PBI-Gordon, says granular products need to be applied when the weed is wet.
“On a granular product, you need it to stick to the weed,” he says. “To make sure that your granular broadleaf product works, it really needs to be applied after the irrigation has applied in the morning, or a heavy due situation.”
For liquid products, he says you have to look at the temperature restrictions on the product, because you can’t apply a liquid post-emergent if it’s too hot or too cold.
In both situations, the weather can’t be windy.
“Most products have a wind restriction because you don’t want it to drift away from the target and hit flowers or ornamentals,” Goodrich says.
The second decision to make is whether you want a selective or non-selective product.
“You’ve got your selective you can put down on everything but it won’t kill your grass, it’ll only kill the broadleaf weed,” says Jeremy Bigler, landscape channel manager with Lebanon. “Or you’ve got the non-selective that will just kill everything. Whatever that stuff touches is going to die.”
He says non-selectives are often used in areas with a grassy weed that can’t be taken out with a pre-emerergent. The only option is to kill out everything in the area of the weed and then reseed and start from the ground up.
No matter the decision, when you apply is most important.
“I would say timing is going to be the key piece to make sure that they’re as effective as they can be,” Bigler says.
Make sure the lawn where the application will occur hasn’t been mowed for a few days so there’s enough foliage growth for the product to stick to the leaves. It’s also important to make sure there will be no watering or rain for the next 24 hours.
Not picture perfect.
“Weed ID is really important,” says Laurence Mudge, green solutions team manager at Bayer. “Making sure you understand what you’re controlling, so you can select the best product for the weed.”
The best product isn’t quite black and white. It depends on your location in the country, the type of grass the weeds are in, and what the current climate is.
Along with a good product, it’s important for your crews to be knowledgeable on what they’re treating. Mudge says there are numerous weeds that are tough to control, and even though there are good products on the market, they’re not perfect.
“It really comes down to expectations,” Mudge says. “Some companies understand these weeds are harder to control and they do a little better job.”
Mudge says the struggle to treat these weeds will depend more on the chemical companies, than the applicator.
“We need more products,” he says. “We need different active ingredients. We just don’t have that many tools in the toolbox for post-emergent herbicides. We’re relying on chemistry that’s really old, but we just haven’t had a lot of active new ingredients come into the post-emergent world.”
Not a cure-all.
Ask any chemical company what LCOs wish their herbicide could do, and the answer is the same.
“There’s really a desire for products that control multiple weed species in a single jug,” Furrer says.
“As the manufacturer, we try to lean that way as well, and make it as easy and simple as possible,” Fausey says.
In the end, the effectiveness of the post-emergent you apply depends on how you apply it.
“The better coverage you can obtain, the more consistent the results will be,” Fausey says. “People that try to cut back on the spray volume or have larger droplets just do not obtain great coverage with the application. Results are going to be variable, but the best way to get more consistent results is to focus on the application itself.”