Crabgrass, a summer annual weed, poses a persistent challenge to homeowners cultivating a dense, healthy Bermuda grass lawn. It germinates rapidly and spreads quickly, often outcompeting the desired turf during warmer months. Bermuda grass is a resilient perennial turf that requires specific management to maintain its density. The primary difficulty is finding a solution that selectively targets the crabgrass without injuring the desirable Bermuda turf. A successful strategy requires a multi-faceted approach, combining proactive chemical applications with sound lawn maintenance practices.
Pre-Emergent Strategies for Prevention
Preventing crabgrass before it appears is the most effective approach to long-term control. Pre-emergent herbicides create a thin chemical barrier at the soil surface, inhibiting the root and shoot development of germinating weed seeds. This protective layer stops new seedlings from establishing themselves in the turf.
The timing of application is critical because the herbicide must be in place before the seeds begin to sprout. Germination typically begins when the soil temperature at a four-inch depth consistently reaches 55 to 60 degrees Fahrenheit. Applying the product too late renders it ineffective, allowing the weed to bypass the chemical barrier.
Products containing active ingredients like prodiamine or pendimethalin are effective choices that are safe for established Bermuda grass. These chemicals offer a long window of control, often lasting between 90 and 120 days. After application, water the lawn lightly to dissolve the product and move the chemical into the top layer of the soil.
Post-Emergent Herbicides Safe for Bermuda
When pre-emergent applications are missed, selective post-emergent herbicides are necessary to eliminate established plants. The primary active ingredient recommended for this task is Quinclorac, which is highly selective and well-tolerated by Bermuda grass. Quinclorac controls crabgrass by disrupting cell wall synthesis, leading to the weed’s eventual death.
This herbicide is effective on younger plants, but it is also capable of controlling more mature plants. For optimal results, Quinclorac should be mixed with a non-ionic or methylated seed oil surfactant. The surfactant helps the chemical adhere to the waxy surface of the crabgrass leaves, ensuring maximum absorption and translocation.
To prevent injury to the Bermuda grass, herbicides should not be applied when temperatures exceed 85 degrees Fahrenheit. High heat increases the risk of turf burn and diminishes the product’s selectivity. Established crabgrass often requires sequential applications, with a second treatment 7 to 10 days after the first, to fully eliminate the weed.
While the older herbicide MSMA was once a common tool for crabgrass control, its use is now highly restricted for residential lawns due to environmental concerns. Quinclorac serves as the modern, safer alternative for post-emergent control. Always check the product label to ensure it is rated for use on Bermuda grass and follow all instructions regarding application rates and temperature limits.
Cultural Practices for Long-Term Control
Long-term prevention relies on promoting a dense, healthy Bermuda grass lawn that naturally suppresses weeds, as chemical control is only one part of a comprehensive strategy.
Mowing Height
The turf’s mowing height plays a significant role in its ability to outcompete crabgrass for sunlight and soil resources. Bermuda grass thrives when mowed low, typically between one and two inches. This encourages dense lateral growth and reduces the space available for weed seeds to contact the soil.
Irrigation
Proper watering favors the deep-rooted Bermuda grass over the shallow-rooted crabgrass. Implementing a deep, infrequent irrigation schedule encourages the Bermuda grass roots to grow deep into the soil profile. Frequent, shallow watering keeps the soil surface moist, creating an ideal environment for crabgrass seed germination.
Fertilization
A consistent fertilization program provides the necessary nutrients for Bermuda grass to maintain its growth throughout the summer. Applying nitrogen during the active growing season ensures the turf is vigorous and dense enough to crowd out annual weeds. A well-fed, properly maintained Bermuda lawn is the best natural defense against crabgrass infestation.