Good defense

As grasses are preparing to go into dormancy, there’s a lot you can do to help them weather the winter and come out on top in the spring. But wet conditions in many parts of the country and drought in others are leading to some challenges throughout the U.S. moving into fall.

“Some of the growth that we have been able to get has been starting to stretch and grasses aren’t quite as healthy as we’d like for them to be,” says Clint Waltz, extension turfgrass specialist at the University of Georgia Turfgrass Research & Education Center. “Then you compound that with disease, so we’ve been fighting some things this year.”

What to watch for.

A wet end to the summer is leading to an increase in crabgrass in many parts of the country, even where preventative measures were taken with pre-emergent herbicides, says Grady Miller, professor and extension turf specialist at North Carolina State University.

“Some people may feel compelled to take out some of the crabgrass before beginning fall overseeding due to the ground coverage from the crabgrass,” he says. “Of course, crabgrass will fade once the temperatures drop.”

Abundant rain means Waltz is seeing a bumper crop of goosegrass and kyllinga, as well as crabgrass. “I don’t know if the wet weather has caused some of the pre-emergent herbicides to degrade a little bit quicker this year or what, but it seems like the crabgrass is a little more extreme this year than it has been,” he says.

Patch diseases are also common in the fall, says Becky Grubbs, Texas A&M AgriLife Extension Service statewide turfgrass specialist. Texas is also seeing a prevalence of take-all root rot in areas that were flooded by Hurrican Harvey.

Where there have been hot and dry conditions, drought stress leads many to believe they have a pest or disease problem, when, in fact, they don’t, says Lindsey Hoffman, assistant professor and extension turfgrass specialist at Texas A&M AgriLife Research and Extension Center. “We’ve been seeing that and sometimes we do see that as caused by some type of insect like a chinch bug but typically what we’re seeing is it’s due to the heat in combination with some sort of drought stress,” she says.

Control methods.

It’s key to know what you’re dealing with before making applications to ensure that you’re solving the right problem. Grubbs recommends sending samples to a diagnostic lab or having an expert visit the site or look at photos.

Once cold weather starts to set in, the first frost will knock back weeds in the lawn so experts don’t recommend applying post-emergent herbicides too late in the year.

“Since you’ve got the environmental conditions coming on to serve as your herbicide, I don’t see that being cost-effective,” Waltz says.

With an abundance of annual bluegrass, researchers have noticed issues with an herbicide resistance in annual bluegrass. Pre-emergents are the best way to deal with it because once annual bluegrass is mature and established, it’s increasingly difficult to get rid of, Grubbs says.

Another important strategy is to keep switching up herbicide chemistries. “We typically recommend not using the same product over and over and over again because you can increase the likelihood of that resistance,” Grubbs says.

“It’s very similar to the discussion around antibiotics or something that you might use to clean. If we are over-using a product or using it at a rate less than what is recommended or more than what is recommended, in all of these cases we increase the likelihood of creating a problem.”

“The best defense against any kind of weed is going to be a healthy stand of grass.” Becky Grubbs, turfgrass specialist, Texas A&M

Feeding time.

Waltz warns against winterizing fertilizer products for warm season grasses like Bermudagrass, centipedegrass, St. Augustine grass and zoysiagrass since the nitrogen content isn’t beneficial moving into cooler weather.

Hoffman and Grubbs also recommend cutting down on the amount of nitrogen going out, applying the last dose six weeks prior to the first frost predicted in your area.

“The reason for that is two-fold,” Grubbs says. “We want to make sure the grass has nitrogen reserves to take with it into the spring but we don’t want to give it too much nitrogen as we’re getting close to fall because nitrogen pushes growth and during that period leading up to dormancy we want that plant to be focusing on its reserves.”

Leading up to fall, grasses should be putting resources into roots and other vegetative tissue like rhizomes and stolons to help them make it through the winter. Applying fertilizer too late in the fall will lead to increased winter kill and applying too early in the spring can lead to a higher instance of disease, she says.

Good management.

Grubbs and Hoffman recommend soil testing twice a year – once in the spring and again two months before your predicted first frost date.

“That way you can make sure the plant has everything it needs to start preparing for dormancy – making sure there’s no imbalances or deficiencies in the soil,” Grubbs says.

Waltz says fall is also a great time to see if lawns are deficient in phosphorus or potassium and make applications, if necessary, to warm season grasses.

Aeration should be done late summer or early fall when grasses are still actively growing and can recover well, Hoffman says. And doing it at a time when there’s adequate water available will also help lawns recover.

That’s a good time to do overseeding or interseeding as well, according to Waltz. The caveat is that you can’t put down seed if you’ve applied herbicide in the past three months since the herbicide will kill the new grass as well as any weeds in the lawn.

“Make sure you know what your maintenance practices have been, what you’ve applied to the lawn because if you go out and apply a pre-emergent herbicide there’s no need to put the seed down,” he says.

Grubbs and Hoffman both recommend an integrated weed management approach, including mowing off weeds and seedheads in fall and winter, and collecting them to keep them from dispersing across customers’ lawns.

“The best defense against any kind of weed is going to be a healthy stand of grass so in the early fall when grass is still active, give it what it needs to compete with weeds,” Grubbs says.