Quickly extinguish your fireweed problem

Fireweed can be a major problem for LCOs because of how fast it spreads. (Photo: Personal Lawn Care)
Fireweed can be a major problem for LCOs because of how fast it spreads. (Photo: Personal Lawn Care)

Fireweed, a rapidly spreading weed, requires annual management by lawn care operators (LCOs). Its emergence in spring poses a threat to lawns, leading to potential takeovers.

Also referred to as American burnweed, this weed started appearing sporadically in lawns and turf areas in the late 1980s, according to Cullen Beard, owner of Personal Lawn Care in Brunswick, Tenn., which offers lawn care services to mostly residential customers.

The outbreaks raised concerns among clients, prompting questions about LCO’s programs. This caused considerable distress among many service providers.

“Fireweed germinates in the spring and grows exceptionally fast thereafter,” says Aaron Hathaway, technical services manager at Nufarm. “(Fireweed) flourishes in turf that lacks regular mowing, such as lawns in the south that undergo biweekly mowing. It commonly appears in dormant warm-season turf that has not been overseeded.”

Chemical control

Fireweed can generate and spread seeds that germinate and establish roots in the thatch above the soil. It can persist and thrive through a preemergence barrier, even if established before germination, Hathaway says.

In these cases, managing the surviving plants requires an LCO either mow them down or make a postemergent herbicide application.

Additionally, Hathaway says herbicides that contain a PPO inhibitor like carfentrazone or pyraflufen-ethyl can help with burndown.

Another approach is using nonselective herbicide applications in dormant turfgrass, like flumioxazin as a preemergent or glufosinate as a postemergent. Other preemergent herbicide options, including dithiopyr, indaziflam, pendimethalin and prodiamine, may offer some control for fireweed and are commonly used to control other problematic weeds found in turfgrass.

Adding a good surfactant with the broadleaf weed control herbicide will improve postemergent control of fireweed, Hathaway adds.

Beard points out that since fireweed emerges from the thatch layer, preemergent herbicides with good soil activity provide limited control. He emphasizes the challenge of timing herbicide applications correctly for effective control and product selection for preventive measures.

Managing fireweed becomes even more challenging due to the varying infestation levels in different years. In instances where fireweed is detected in turfgrass, postemergent herbicides like 2,4-D, triclopyr plus fluroxypyr and MCPA plus fluroxypyr plus dicamba offer effective control in warm-season turfgrass cultivars, Hathaway notes.

LCOs relying on preemergent herbicides need to be vigilant, especially considering fireweed’s emergence from the thatch layer.

A diverse approach?

Combining preemergent and postemergent herbicide treatments enhances fireweed control. For instance, products containing 2,4-D plus MCPP plus dicamba demonstrate superior control compared to 2,4-D alone, according to Beard.

Adding metsulfuron methyl to this mixture, along with close mowing every seven to 10 days, results in excellent fireweed control. He recommends a tactical approach for LCOs to reduce outbreaks, such as applying prodiamine within three weeks of fireweed germination.

Also, combining indaziflam with prodiamine in split applications not only enhances fireweed control but also addresses other troublesome turfgrass weeds like goosegrass and doveweed.

Mechanical control methods

Fireweed roots in the thatch layer, making hand pulling or mowing an effective method. Hathaway says that pulling or popping fireweed plants out of the ground with a tool can be effective unless there are too many plants to control mechanically or the area is too large to cover efficiently.

Ultimately, experts say combining carefully selected preemergent and postemergent herbicide applications with mechanical control methods proves to be the most effective approach to control fireweed and prevent its spread

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George Kegode, Ph.D.

George Kegode, Ph.D., is a consultant and writer specializing in pest and weed management based in Missouri.

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