Controlling Torpedograss

by | Aug 18, 2021 | Integrated Pest Management, Invasive Species, Lawns, Pesticides, Pests, Turf

One of the most conspicuous outcomes from Hurricane Michael was the complete disruption of local lawns and landscapes.  Giant holes where tree roots once existed, ruts and compacted ground from clean-up equipment, and formerly shaded acres flooded with fresh sunshine were three very common situations property owners suddenly found themselves faced with.  An unforeseen consequence of all this newly bare ground ripe was the intrusion by a variety of very aggressive weeds.  One invasive exotic weed that has made itself right at home in many county landscapes following Michael and that I’ve seen lots of lately is Torpedograss (Panicum repens).

Often brought into landscapes with “fill-dirt” and “topsoil” applications or spread through mowing, Torpedograss is an aggressive perennial grass in the same plant family as Bermudagrass and Cogongrass.  Like many invasive exotic species, Torpedograss was introduced into the United States in the late 1800’s from its native Africa and Asia as a potential forage crop.  Unlike its cousin Cogongrass, the Torpedograss is highly palatable to cattle and so gained a quick following among the ranching community.  Unfortunately, over the next century, Torpedograss had left the pasture and turned into one of the biggest pest plants in Florida, ruining many a lawn, taking over 70% of the state’s public waterways, disrupting native marshlands, and costing Florida over $2 million a year to control!

Torpedograss growing in a Calhoun County gravel driveway. Photo courtesy of Daniel Leonard.

Torpedograss spreads rapidly through underground, sharply pointed, white-colored, “torpedo-like” growing tips and can dominate wet or dry areas in short order.  The species often hides in lawns when mixed in and mowed with other turfgrasses (especially Zoysiagrass, which it closely resembles), growing unnoticed until infestations are severe and control options are few.  This makes scouting for the weed and accurate identification crucial!  Torpedograss can be identified by its bluish-green leaf and stem color, hairy leaf edges, stiff overall appearance, distinctive panicle-type flowers, and can grow quickly to 3’ or so in height, spreading indefinitely.  Though it initially can resemble other turf species, once you know what you’re looking for, Torpedograss stands out visually amongst its competitors.

After identifying Torpedograss, control methods can be chosen depending on the site it has infested.  In lawns, options vary based on turf species.  If infestation occurs in the common Centipedegrass and Bahiagrass lawns of the Panhandle, options are few.  Products with the active ingredient Sethoxydim (Poast, Fertilome Over the Top, Southern Ag Grass Killer, etc.) can suppress Torpedograss growth in these situations but will not destroy it and are not permanent options.  If the area infested is not large, killing the whole spot out with a non-selective herbicide like Glyphosate (Roundup and generics) and then resodding is probably a better option.  In Bermudagrass or Zoysiagrass lawns, products with the active ingredient quinclorac (Drive and generics) are very effective at controlling Torpedograss without having to go the “nuclear” glyphosate route.  Unfortunately, there are no effective controls for Torpedograss in St. Augustinegrass lawns.

In landscaped beds, Torpedograss is somewhat easier to control.  Hand pulling in beds can be effective where new invasions occur but are impractical once the weeds gain a strong foothold.  Once that occurs, chemical control is required.  In bare or mulched areas away from plants, careful spot spraying in bare areas with a 2-3% glyphosate solution is extremely effective.  Where the Torpedograss has grown into and through landscape plants, an “over-the-top” application of fluazifop (Fusilade) will take out the weed without harming most ornamental plant species!  (Be sure to check the Fusilade label to make sure your ornamental plant species are safe to apply to!)

Torpedograss is one of the most serious, yet overlooked, invasive plants that occurs in Florida.  However, through prevention and control techniques like cleaning mowers when mowing infested areas, accurate identification, and prompt, effective herbicide use, you can keep the weed from taking over your lawn and landscape!  For assistance in identifying and controlling Torpedograss and other lawn weeds, contact your local UF/IFAS County Extension office!  Happy gardening!

 

Daniel J. Leonard
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