This postemergent mesotrione application on crabgrass resulted in bleached plants. Similar effects could happen with topramezone applications. (Photo: Aaron Hathaway, Nufarm)
It’s that time of year again when crabgrass and goosegrass attempt to outcompete turfgrass species and take over lawns. However, there is hope. Aaron Hathaway, technical services manager for Nufarm, and Dean Mosdell, technical manager for Syngenta, share some expert advice on how preemergent and postemergent herbicide applications work to give you the best control of these turf weeds.
Postemergent control
Experts say it’s difficult to control crabgrass and goosegrass after emergence and usually provides mixed results. A commonly used herbicide for crabgrass control is quinclorac. However, lawn care operators (LCOs) should add a non-ionic surfactant to quinclorac for the best results. Hathaway adds that quinclorac does not work well with crabgrass seedlings between one- to three-tiller stages. Also, quinclorac does not control goosegrass.
Mesotrione is another postemergent herbicide option for LCOs to control crabgrass, but experts say it will not control goosegrass.
“Mesotrione can also provide some preemergence control because it persists in the soil after application and can prevent crabgrass seedlings from emerging,” Mosdell says.
Though there are few postemergent herbicide options for goosegrass, experts say sulfentrazone or topramezone — when applied with a non-ionic surfactant — will provide good control. Mosdell says applicators must pay close attention to turfgrass species and product labels to avoid herbicide injury when using these postemergent herbicides.
Many postemergent herbicides act systemically and have a narrow window when pros can apply them without injuring established turf. In contrast, preemergent herbicides are safe on established turf because they prevent seedling emergence.
In cool-season turf, pros can use fenoxaprop-p-ethyl for postemergent control of crabgrass and goosegrass. However, Hathaway says fenoxaprop-p-ethyl is incompatible with major broadleaf weed control herbicides commonly used as tank-mix partners.
To prevent crabgrass and goosegrass infestations, Mosdell says pros should not mow turf too low, should use proper irrigation and should aerate turf in the fall. Hathaway adds that if pros identify crabgrass and goosegrass infestations late in the season, the best option is to use postemergent herbicide applications to minimize weed seed production and begin the following season with a good preemergent crabgrass and goosegrass control program.
Preemergent control
For the best preemergent crabgrass control, experts say pros should apply dinitroaniline herbicides — such as pendimethalin, trifluralin and prodiamine — as soon as the snow melts.
“Dinitroaniline herbicides are safe to use on cool-season and warm-season turfgrass, and they have a residual effect that enhances the ability to prevent crabgrass from emerging,” says Hathaway. “The first split application should be the full label rate of the dinitroaniline herbicide while the second split application should be half the full rate.”
Alternatively, following the first split application of dinitroaniline herbicide, Hathaway says pros can apply a full label rate of dithiopyr as the second split treatment to control crabgrass.
“Dithiopyr can also be applied in two split applications for crabgrass control, and since it has some early postemergence activity, it can control crabgrass seedlings missed by the dinitroaniline herbicide used in the first split application,” says Hathaway.
Experts say indaziflam is another option for preemergent control of crabgrass and is safe to use on warm-season turfgrass.
Goosegrass control is more problematic because of late germination compared to crabgrass. Dinitroaniline herbicides such as dithiopyr and indaziflam will provide good control when LCOs use the highest label and properly time split applications.
Mosdell says because goosegrass is common along driveways and areas with compacted soil, such as walkways, using the highest label rate for both split applications of a dinitroaniline herbicide will provide good preemergent control of goosegrass.
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