Foxtail is a problematic annual or perennial grass that rapidly invades pastures, hayfields, and disturbed soil. Its spiky, bristled seed heads are hazardous to grazing livestock and compete aggressively with desirable forage species. Foxtail is a prolific seed producer, and its presence devalues hay by making it unpalatable and potentially harmful to animals. Eliminating foxtail requires an integrated, multi-year strategy combining mechanical control, targeted herbicide use, and long-term improvements to pasture health.
Identifying Foxtail Varieties and Associated Risks in Pastures
The most common varieties found in pastures are the annual species: green foxtail (Setaria viridis), yellow foxtail (Setaria pumila), and giant foxtail (Setaria faberi). These summer annuals germinate in the spring when soil temperatures reach approximately 60°F and complete their life cycle by late autumn. Perennial species, such as knotroot foxtail (Setaria parviflora), are also persistent because they spread by short rhizomes.
Identification is possible before the distinctive, brush-like seed head appears by examining the collar region where the leaf blade meets the stem. Foxtail species feature a fringe of hairs, known as a ligule, which distinguishes them from many desirable forage grasses. The greatest danger occurs when the plant matures and produces its seed head, which contains sharp, backward-facing awns.
These awns can embed themselves in the soft tissues of grazing animals, commonly the gums, tongue, nostrils, and eyes of horses and cattle. Once embedded, the barbs prevent the awn from being expelled, allowing it to migrate deeper into the tissue. This mechanical damage leads to painful ulcers, abscesses, and infections, resulting in decreased feed intake and weight loss. Mature foxtail plants are also less palatable and have poor digestibility, reducing the quality of contaminated hay.
Mechanical and Cultural Eradication Strategies
Mechanical control aims to interrupt the foxtail’s life cycle before it can drop viable seed and replenish the soil’s seed bank. Strategic mowing is an effective cultural practice, but timing is paramount. Mowing must be performed when the seed head is in the “boot stage,” meaning the seeds are developing inside the sheath but have not yet fully emerged or hardened.
Regular, close mowing is ineffective because the plant adapts by producing new, shorter seed heads below the cutting height. Instead, a well-timed, high mowing followed by the removal of the cuttings can prevent seed dispersal for the season. For small, isolated patches, physical removal is the most immediate and effective method, but the entire plant, including the fibrous root system, must be dug out.
Proper disposal of plant material is necessary to prevent re-infestation. Never compost mature foxtail seed heads, as the seeds can remain viable and spread when the compost is used. For severely infested pastures, a complete renovation approach may be necessary, involving tilling the soil to bury the existing foxtail plants.
Tillage can bring dormant seeds to the surface, so the area should be allowed to germinate and then be tilled or sprayed again to exhaust the seed bank before re-seeding. Cultural controls include managing nutrient levels, as foxtail thrives on excessive nitrogen. Reducing nitrogen application during the foxtail’s peak spring germination period helps reduce its competitive advantage over desirable grasses.
Selective Herbicide Application for Control
Chemical control of foxtail is challenging because it is a grassy weed growing within a grass pasture, severely limiting the use of selective herbicides. The two primary chemical strategies involve using pre-emergent products to prevent germination and post-emergent products to kill actively growing plants.
Pre-emergent herbicides, which contain active ingredients like pendimethalin, must be applied in late fall or early spring before the soil temperature reaches the 55°F to 60°F range necessary for germination. These products form a chemical barrier on the soil surface, preventing the foxtail seed from sprouting. Split applications, with a second treatment following the first hay cutting, are recommended for season-long control of annual species.
Post-emergent products, such as those containing nicosulfuron and metsulfuron, are only effective when applied to young, actively growing plants before the seed head emerges. These selective options are primarily labeled for use in warm-season grasses like Bermudagrass. They often risk stunting the desirable forage, which can result in yield loss. Post-emergent applications require a careful review of the label, as many carry grazing or haying restrictions that must be observed for livestock safety.
Long-Term Pasture Management and Prevention
The most sustainable method for controlling foxtail is to modify the pasture environment to favor the growth of desirable forage species, as foxtail is highly susceptible to competition and shading. This process begins with a comprehensive soil analysis to determine the current pH and nutrient balance. Foxtail often capitalizes on compacted ground and soil that is deficient in nutrients or has an imbalanced pH.
Correcting the soil pH through the application of lime is a long-term cultural strategy that supports the growth of perennial grasses and legumes. For cool-season grasses like tall fescue, the optimal pH range is 6.2 to 6.5, while legumes require a slightly higher pH of 6.5 to 7.0. Ensuring adequate phosphorus and potassium levels promotes a dense, competitive stand of forage.
Overseeding the pasture with aggressive, shade-producing species, such as tall fescue, perennial ryegrass, or clover, helps to outcompete foxtail seedlings. These competitive forages establish a thick canopy that shades the soil surface, suppressing foxtail germination and growth. Overseeding is most effective when done in the late summer or early autumn to allow the new plants to establish before the foxtail begins spring germination.
Implementing a rotational grazing system is a key management practice. Overgrazing creates bare patches and exposes soil, providing the perfect environment for foxtail to colonize. Rotational grazing ensures that a minimum stubble height, such as three inches for fescue, is maintained, which promotes vigorous root growth and a dense canopy that shades out foxtail seedlings.