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Is it Safe to Apply Herbicides
During Spring Green-up for Turfgrasses?

Patrick McCullough
Extension Turf Weed Scientist, University of Georgia

Tank-mixing herbicides may improve the spectrum of weeds controlled in single applications which saves time and labor in turf weed control programs. Mixing compatible herbicides from different chemical families may improve control of specific weed populations, such as 2,4-D applied with dicamba for broadleaf weeds.  Herbicide combinations may also provide control of several weed types at the same time, such as grassy and broadleaf weeds.  For example, turf managers often apply 2,4-D with quinclorac (Drive) to control broadleaf weeds and crabgrass in the summer.

Prepackaged formulated mixtures of herbicides have been effective tools for weed control in the turf industry for years. Mixtures of broadleaf weed herbicides in products like Trimec Classic (2,4-D + dicamba + MCPP), Speed Zone (carfentrazone + 2,4-D + dicamba + MCPP), and Escalade (fluroxypyr + 2,4-D + dicamba) are often more economical to apply than multiple treatments of individual components.  Recently, chemical companies have begun marketing new combination products containing three or four active ingredients for controlling grassy weeds, broadleaf weeds, and sedges.  These products include Echelon (sulfentrazone + prodiamine), One-Time (quinclorac + MCPP + dicamba), Q4 (sulfentrazone + quinclorac + 2,4-D + dicamba), and Surge (sulfentrazone + dicamba + 2,4-D + MCPP).

These new combination products offer unique tools for controlling many different types of weeds with one prepackaged formulated product.  Although these mixtures are interesting product concepts, turf managers must note the pounds of active ingredient of each individual component that are applied in these combinations and compare them with rates required for controlling targeted weeds.  For example, Q4 contains sulfentrazone, quinclorac, 2,4-D, and dicamba at 0.06, 0.5, 0.88, and 0.1 pounds per gallon, respectively.  This combination of herbicides may provide excellent broadleaf weed control but the product lacks sufficient concentrations of sulfentrazone and quinclorac for controlling sedges and crabgrass, respectively, at labeled rates.  Turf managers targeting broadleaf weeds, crabgrass, and sedges need to add at least 0.06 lb a.i. per acre of sulfentrazone (Dismiss) and 0.25 lb a.i. per acre of quinclorac (Drive) when applying Q4 at one gallon of product per acre (the highest labeled rate) to meet concentrations required for control.

Other herbicides like One-Time (quinclorac + dicamba + MCPP) and Echelon (sulfentrazone + prodiamine) offer similar opportunities for controlling different weed populations but it is important to note the concentrations of the components before application.  One-Time is labeled from 21 to 64 fluid ounces of product per acre and is marketed for crabgrass and broadleaf weed control.  In order to deliver the 0.75 lb a.i. per acre of quinclorac required for crabgrass control, One-Time must be applied at 64 oz per acre.  Lower label rates may control broadleaf weeds but quinclorac concentrations may be insufficient for effective crabgrass control in turf.

Echelon is a preemergence herbicide with prodiamine and sulfentrazone mixed at a 2:1 ratio, respectively, for crabgrass and sedge control.  Rates registered for bermudagrass (24 to 36 fl oz/acre) are higher than rates for other turfgrass species (8 to 24 fl oz/acre), and thus, turf managers may compromise pounds of active ingredients applied per acre in certain grass species.  At 24 fl oz of Echelon per acre, turf managers would apply 0.25 lb of sulfentrazone per acre but only 0.5 lb of prodiamine compared to 0.65 to 0.75 lb per acre that is required.  Turf mangers may wish to add more prodiamine (Barricade or Cavalcade) to raise the concentration for controlling annual weeds, such as crabgrass, in the spring and summer.

This trend in herbicide combination products will likely continue in the turf industry.  It is important for users to read product labels and calculate active ingredients of components in these products to effectively control weeds.  Furthermore, individual herbicides may need to be purchased separately if raising the concentration in combination products is required for specific weeds.  While these new products present new options for weed control, the concentration of components in these mixtures must be understood in order to meet turf weed control requirements. 

 

Please share this information with others in the landscape & turf industry. For more information:

Call your local Extension Agent at (800) ASK-UGA1 or locate your local Extension Office at http://www.caes.uga.edu/extension/statewide.cfm

www.georgiaturf.com has a section on identifying weeds under Pest Management and weed control recommendations under the 2009 Turfgrass Pest Control Recommendations.

Pest Management Handbook (Follow all label recommendations when using any pesticide) - www.ent.uga.edu/pmh/

 

For more Landscape Alerts please visit the Georgia Center for Urban Agriculture

 

   

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