Quinclorac is a selective herbicide commonly used in lawn and turf management programs. Nutsedge is a persistent weed that can quickly invade a lawn, often mistaken for a common grass. This article explores the specific functions of Quinclorac and explains why a different chemical approach is necessary to effectively manage nutsedge.
What Quinclorac Effectively Controls
Quinclorac is a selective, post-emergent herbicide belonging to the quinoline carboxylic acid family. It functions systemically as a synthetic auxin, mimicking natural plant growth hormones after absorption through the foliage and roots. This chemical signal disruption leads to uncontrolled cell expansion and abnormal tissue development, ultimately causing the plant’s death.
This mechanism makes it highly effective against a variety of common, stubborn weeds in turfgrass. Its primary use is controlling annual grassy weeds, most notably crabgrass, even in mature stages. Quinclorac also eliminates certain broadleaf weeds, such as clover, dandelion, and speedwell. This selectivity allows it to target invasive weeds while leaving most desirable turfgrass species unharmed.
Why Quinclorac Fails Against Nutsedge
Quinclorac is ineffective against nutsedge because nutsedge is a sedge, not a grass, belonging to a taxonomically distinct plant family. Sedges have a unique physiological structure that prevents Quinclorac from working correctly, unlike the annual grasses it is designed to kill. The most significant difference is the stem structure; nutsedge has a characteristic triangular stem, while grasses have a hollow or rounded stem.
Nutsedge spreads aggressively through underground rhizomes and produces small, starchy tubers called nutlets, which can remain dormant in the soil for several years. Quinclorac’s systemic action is not potent enough to overcome this complex, regenerative growth pattern. Even if a small amount of Quinclorac is absorbed by the foliage, the herbicide typically only damages the shoot without translocating in high enough concentrations to kill the deeply buried, energy-rich nutlets. The tubers possess enough reserve energy to quickly sprout new shoots, making a single application of Quinclorac useless for long-term control.
Effective Herbicides for Nutsedge Control
Controlling nutsedge requires a specialized herbicide formulated to move throughout the plant and reach the underground tubers. These chemicals belong to different classifications than Quinclorac and are designed to target the unique sedge physiology. The most effective active ingredients for post-emergent nutsedge control are Halosulfuron-methyl and Sulfentrazone.
Halosulfuron-methyl is a sulfonylurea herbicide that works by inhibiting the acetolactate synthase (ALS) enzyme in the nutsedge plant, which is necessary for the synthesis of certain amino acids. This disruption halts cell division and growth, allowing the chemical to travel systemically and kill the nutlets.
Sulfentrazone is another powerful sedge control agent that works by inhibiting protoporphyrinogen oxidase (PPO), causing cell membrane disruption and rapid plant death. Both Halosulfuron-methyl and Sulfentrazone are selective herbicides, meaning they can be applied to most common turfgrasses without causing significant injury. Imazosulfuron is also effective, working by inhibiting the ALS enzyme. These chemicals are formulated to achieve the necessary systemic movement into the tubers, which is the only way to achieve long-term eradication of nutsedge.
Safe Application of Nutsedge Herbicides
Optimal timing for nutsedge herbicide application is when the weed is actively growing but before it begins to form tubers, typically in late spring or early summer. Applying the product when the nutsedge is young and growing rapidly allows for better absorption and systemic movement throughout the plant.
Since nutsedge leaves have a slick, waxy surface, a non-ionic surfactant must be included with the herbicide mixture to help spray droplets adhere and penetrate the foliage. The application should be made to dry grass. Check the product label for the required rain-fast period, which is the time needed for the herbicide to dry before rainfall or irrigation.
Many nutsedge herbicides require a follow-up application, typically four to six weeks later, to target new shoots emerging from previously dormant tubers. Always wear appropriate personal protective equipment (PPE), such as gloves and eye protection, and strictly follow the product label’s instructions for mixing ratios and safety precautions.