Stay a step ahead of herbicide resistance in crabgrass and goosegrass

Fertility management, combined with disease and insect control are keys to keep crabgrass at bay. (Photo: Syngenta)

Crabgrass and goosegrass are annual weeds that germinate in the spring, grow rapidly throughout the summer, mature in late summer and produce numerous seeds before dying out at the first frost in autumn. Both species have a history of developing herbicide resistance. When weeds become resistant to a herbicide, lawn care operators (LCOs) lose a valuable tool and it becomes more difficult to control the weed.

Ian Rodriguez, Ph.D., technical services manager for Quali-Pro; Bret Corbett, product development manager for Albaugh; Lisa Beirn, Ph.D., technical services representative for Syngenta; and Aaron Hathaway, technical services manager for Nufarm, share what LCOs should know about managing crabgrass and goosegrass to minimize or prevent herbicide resistance.

Factoring in resistance

Corbett says LCOs have few herbicide active ingredients available for crabgrass and goosegrass control, which makes resistance management challenging. 

“Crabgrass and goosegrass can both produce numerous seeds with a variety of herbicide resistance mutations,”
says Rodriguez. 

Both species can easily cross-pollinate with other biotypes, which helps spread resistant genes, Hathaway says. The problem is exacerbated when crabgrass and goosegrass seeds spread to new areas.

Applying an active ingredient or using herbicides with a similar mode of action repeatedly for several years can cause resistance, Beirn says. 

Experts say dinitroaniline herbicides — such as pendimethalin, indaziflam, trifluralin and prodiamine — are good options for preemergent crabgrass control. The dinitroaniline herbicides dithiopyr and indaziflam are good options for goosegrass control. LCOs often use quinclorac and mesotrione for postemergent crabgrass control. When used with a non-ionic surfactant, sulfentrazone or topramezone are postemergent options for goosegrass. LCOs could also opt for fenoxaprop-p-ethyl for postemergent control of crabgrass and goosegrass on cool-season grasses.

Timing matters

When it comes to crabgrass and goosegrass, preemergence herbicides are the best option, says Hathaway. 

Corbett notes LCOs can opt for split applications to help extend control of crabgrass and goosegrass. According to the University of Nebraska Extension, to make a split application, LCOs put half the highest recommended rate in early spring and the other half 6-8 weeks later.

Crabgrass starts emerging when the soil temperature reaches 55 degrees F for three to four days in a row, Rodriguez says. LCOs should apply preemergent herbicides as soon as soil temperatures reach that threshold.

“Depending on your location in the U.S., goosegrass begins to emerge when the soil temperature is between 63 and 65 degrees F,” Beirn says.

She stresses that LCOs need to time preemergent applications to coincide with the soil temperature to ensure herbicide efficacy.

Keys to success

It’s critical for LCOs to choose the right preemergent herbicide for their growing zone, Corbett says. 

“Picking the right herbicide, making timely application and dealing with the elements as they come (are important),” he says.

Next, LCOs must ensure their equipment is properly calibrated, their application timing is correct, and they irrigate after application. 

Other keys to crabgrass- and goosegrass-free turf are good cultural controls like fertility management and disease and insect control, Rodriguez says.

“Develop a good turfgrass management program that combines cultural practices with proper herbicide use and use a soil temperature prediction tool to help with timing preemergent applications,” Beirn says. “Mowing at a height of 2 to 3 inches and irrigating deeply and less frequently (once weekly) are good cultural management practices LCOs should always remember.”