Bermuda grass is a highly popular turf choice across warm climates because of its exceptional resilience, heat, and drought tolerance. This warm-season grass is known for its aggressive growth habit, using both above-ground runners (stolons) and underground stems (rhizomes) to create a dense, durable lawn surface. Even this tough turf is susceptible to various pests that can transform a lush green yard into a patchy brown landscape. Identifying what is eating your Bermuda grass is the first step in effective management, as different pests require completely different control strategies. This guide will help homeowners distinguish between pests that attack the grass blades and those that strike at the roots, providing specific solutions to protect the turf.
Identifying the Cause: Surface-Feeding Pests
Pests that feed on the grass blades and stems cause highly visible damage, often making a healthy lawn appear “scalped” or chewed overnight. Two common culprits are the Sod Webworm and the Fall Armyworm, both of which are the larval stage of moths. They feed primarily at or just above the soil line, consuming the green tissue of the plant.
Sod webworms are the larvae of small, brownish-gray moths that fly in a jerky, zigzag pattern low over the turf, typically at dusk. The caterpillars are about three-quarters of an inch long, ranging from greenish to tan, and often hide in silk-lined tunnels within the thatch layer during the day. Their damage appears as small, irregular brown patches that look like the grass was closely mowed, with blades chewed off near the soil surface. Webworms leave behind silken webbing and tiny, green fecal pellets, or frass, near their feeding sites.
Fall armyworms are destructive caterpillars known for appearing suddenly and moving in large groups. These pests are identified by a distinct inverted “Y” shape on their head capsule and stripes running down their bodies. Armyworm damage is characterized by rapid defoliation, where large sections of turf are eaten down to the crown, leaving a scorched or scalped appearance. The adult moths are migratory, often moving north from Gulf Coast states in late summer and fall, which can lead to unexpected, massive infestations that destroy turf quickly.
Distinguishing between the two often comes down to the speed and pattern of the damage. While both cause brown patches, armyworms tend to strip the leaf tissue down completely, often leaving a distinct line between damaged and healthy grass as they “march” across the lawn. Sod webworms, conversely, work from the thatch layer, leaving more scattered, smaller patches of chewed grass that contain their characteristic silk and frass. The “soap flush” test, involving pouring a mixture of dish soap and water over a small area, can bring both types of caterpillars to the surface for positive identification.
Subsurface Attackers and Mite Issues
Damage such as wilting or thinning despite adequate watering often points to pests that attack below the soil surface or are microscopic. These pests compromise the plant’s ability to absorb water and nutrients, leading to a decline in turf health.
Mole crickets, particularly the tawny and southern species, are subterranean insects that use their shovel-like front legs to tunnel just beneath the surface. While they consume roots, their main damage is mechanical: their tunneling activity severs the roots and uproots the turf, creating raised, spongy ridges or mounds of soil. The affected areas feel loose underfoot, and the grass quickly turns brown and dies because the root system is detached from the soil. The soap flush test can confirm the presence of mole crickets, which are about one to one-and-a-half inches long with beady eyes and a hard, brown body.
Nematodes, especially plant-parasitic species like the sting nematode, are microscopic roundworms that feed on grass roots. Sting nematodes are among the most damaging to Bermuda grass and thrive well in sandy soil environments. They use a needle-like mouthpart to puncture root cells and extract nutrients, causing the roots to become short, stubby, and dark. Above-ground symptoms include irregular patches of thinning, yellowing turf that fails to respond to fertilizer or irrigation. Diagnosing a nematode problem requires sending a soil sample to a diagnostic lab for a professional count and identification.
The Bermuda grass mite is a nearly invisible arachnid that feeds exclusively on Bermuda grass. These mites are so small they cannot be seen without a ten- to thirty-power hand lens. They feed by injecting toxins into the plant under the leaf sheath, which severely shortens the internodes. This toxic feeding leads to a distinct symptom known as “witches’ broom,” where the grass stems become stunted, distorted, and tufted, giving the turf a dense, matted, and unhealthy appearance. Infested turf often turns yellow and develops thin or bare patches, especially noticeable in late spring and summer.
Integrated Strategies for Pest Control
Effective control of Bermuda grass pests relies on an integrated pest management (IPM) approach, combining cultural practices, biological controls, and targeted chemical treatments. The goal is to build a healthy, resilient turf that can withstand pest pressure.
Cultural controls focus on maintaining optimal turf health to minimize stress and prevent infestations. Bermuda grass should be mowed at a low, appropriate height (typically 0.5 to 1.5 inches) to reduce leaf tissue available for surface-feeding pests and discourage mite habitat. Proper irrigation is equally important; deep, infrequent watering encourages a robust root system, making the turf more tolerant of root-feeding pests. Over-fertilizing with nitrogen should be avoided, as high nitrogen levels increase susceptibility to pests like mites and armyworms.
Biological controls use natural enemies to manage pest populations. For subterranean pests like mole crickets and certain nematodes, applying beneficial nematodes, such as Steinernema carpocapsae or Heterorhabditis bacteriophora, can be effective. Encouraging natural predators like birds, which feed heavily on surface caterpillars, also helps suppress populations of armyworms and webworms.
Chemical controls are reserved for severe infestations. For surface-feeding caterpillars, contact insecticides like spinosad or bifenthrin provide quick knockdown and are best applied in the late afternoon. Mole crickets respond well to granular baits or systemic insecticides, most effective when applied in late spring or early summer to target the younger nymph stage. Nematode control often requires specialized nematicides, typically applied by professionals.