Atrazine is a widely used chemical in lawn care, often included in weed-and-feed products designed for specific warm-season grasses. Homeowners and turf managers frequently ask if this herbicide can eliminate aggressive perennial Bermuda grass (Cynodon dactylon). The confusion arises because Atrazine effectively controls many common lawn weeds while leaving desirable turf unharmed. Understanding its effect requires examining the chemical’s mechanism and the plant’s biology.
Atrazine’s Specific Mechanism and Target Weeds
Atrazine is classified as a triazine herbicide that disrupts photosynthesis in susceptible plants. It works as a photosystem II (PSII) inhibitor, binding to proteins in the chloroplasts responsible for the electron transport chain. This binding halts the plant’s ability to convert light energy into chemical energy, effectively starving the weed. The visible result is chlorosis, or yellowing, followed by necrosis and eventual plant death.
The herbicide is valued for its selectivity, controlling certain weeds without injuring the desired turfgrass. Atrazine is designed to control a wide spectrum of annual broadleaf weeds, such as clover, dollarweed, and henbit, along with certain annual grassy weeds like annual bluegrass. This selective action makes it a staple for maintaining Southern lawns, especially St. Augustine and Centipede grass. These grasses possess natural tolerance mechanisms that rapidly detoxify the chemical. The chemical is absorbed by the roots and foliage, making it effective as both a pre-emergent and post-emergent solution.
Atrazine’s Effect on Bermuda Grass
Despite its strength against many weeds, Atrazine is not an effective solution for killing established, perennial Bermuda grass. This is because Bermuda grass, like other tolerant warm-season turf species, has a robust metabolic defense system to counteract the herbicide. The plant quickly metabolizes or detoxifies the Atrazine before it reaches lethal concentrations in the tissues responsible for energy production.
This detoxification process often involves conjugation with glutathione, rendering the chemical harmless. While a heavy application may cause temporary damage, such as slight yellowing or stunting of the foliage, it will not provide systemic control. The deep, extensive network of rhizomes and stolons that characterizes established Bermuda grass is protected from the herbicide’s effects by rapid detoxification. Therefore, Atrazine is often used as a selective herbicide in Bermuda grass lawns to remove broadleaf weeds because the desirable grass is tolerant to it.
Selective Control of Bermuda Grass
Since Atrazine fails to eliminate established Bermuda grass, alternative strategies are required, depending heavily on the location of the invasive grass. For removal in non-turf areas, such as flowerbeds or alongside driveways, non-selective herbicides are the most reliable option. Products containing glyphosate are commonly used because they are absorbed by the foliage and translocated to the root system, offering a systemic kill. The product must be applied to actively growing grass, and multiple applications are often necessary to exhaust the energy reserves stored in the rhizomes.
Controlling Bermuda grass when it is invading a desirable lawn, such as St. Augustine or Zoysia, demands a highly selective approach. This is challenging because both the weed and the desired grass are technically grasses. Effective programs often rely on post-emergent selective herbicides containing active ingredients like fluazifop, fenoxaprop, or quinclorac, which offer a better margin of safety for the surrounding turf. Multiple, sequential applications of these selective herbicides are required to suppress the Bermuda grass over a period of weeks or months. Success also relies on maintaining the desired turf at a high mowing height and promoting its health to help it outcompete the weakened Bermuda grass.