Back to top

Active Ingredient Overview: Quinclorac

Printer-friendly version
December 15, 2016

Quinclorac is an herbicide used for managing weeds in turf, and is available alone as a single herbicide or in combination products with other turf herbicides. Quinclorac controls certain annual grasses, and also has activity on several annual and perennial broadleaf weeds. When herbicide products containing quinclorac are applied with the correct timing, these products can serve as a strong weed management tool.

Cool-season turfgrass species tolerance:

  • Kentucky bluegrass
  • tall fescue
  • perennial ryegrass
  • fine fescue (tolerance variable, use only when fine fescue is part of a turf stand with other cool-season turf species)

Mode of action and symptomology:

Quinclorac acts as an auxin mimic and is classified as a quinolone carboxylic acid. It is absorbed by the foliage and translocated throughout the plant. Symptoms exhibited by broadleaf weeds include leaf and stem curling or twisting, and necrosis. Susceptible grasses show signs of stunted growth, chlorosis (whitening) and slow reddening followed by necrosis and death.

Postemergence control of annual grassy weeds:

  • barnyardgrass
  • crabgrass (smooth and large) - not effectively controlled when grasses are in the 2- to 4-tiller stage of growth
  • yellow foxtail - not effectively controlled when grasses are in the 2- to 4-tiller stage of growth

Postemergence control of broadleaf weeds:

  • birdsfoot trefoil - not a common weed in quality turf, but can be useful in eliminating populations before renovation
  • dandelion
  • field bindweed - not a common weed in quality turf, but can be useful in eliminating populations before renovation
  • horseweed - can be used in late season to manage this winter annual
  • white clover - commonly accepted as one of the best herbicides for control of this weed

NOTE: combination products (quinclorac with other broadleaf herbicides) with increase this somewhat limited control spectrum of species.

Used as part of seeding/overseeding of cool-season turfgrasses:

Quinclorac, as a single component of a product, can be used as part of a weed management program during the establishment (seeding or overseeding) of cool-season turfgrasses. The product label will indicate the application timing during seeding/overseeding and the establishment period for particular turfgrass species.

Adjuvant/surfactants requirement for postemergence applications:

Dependable postemergence weed control results with quinclorac-only products require addition of a spray adjuvant (MSO – methylation seed oil or COC – crop oil concentrate) as a component of the final spray solution.

Some precautionary statements:

  • NOT for use in ornamental landscape beds, as quinclorac products are not labeled for this use.
  • Turf clippings from treated turf should NOT be used as a mulch or compost near flowers, vegetables, or ornamental trees and shrubs.
  • Avoid mist or overspray onto areas that are not turf.

Summary:

This active ingredient has great utility as a component of a turf weed management program. Some unique characteristics of the herbicide, including its performance on mature crabgrass and yellow foxtail, as well as providing very effective white clover control, set it apart from other turf herbicides.

 - Randall G. Prostak, UMass Extension Weed Specialist

Topics: 
Commercial Horticulture