Barnyard grass (Echinochloa crus-galli) is a fast-growing summer annual weed that poses a significant challenge in lawns, gardens, and agricultural fields. It is often called cockspur grass or watergrass due to its preference for moist, disturbed soils. A single plant can produce tens of thousands of seeds, ensuring rapid establishment and spread. Since the seeds can remain viable for several years, a comprehensive approach is necessary to manage current infestations and prevent recurrence. This article guides immediate and long-term strategies for controlling this weed.
Identifying Barnyard Grass and Understanding Its Growth Cycle
Accurate identification is the first step toward effective control. Barnyard grass is characterized by coarse, pale green leaves, typically ¼ to ½ inch wide, growing in dense, upright clumps up to five feet tall. A unique feature distinguishing it from many other weedy grasses is the complete absence of a ligule or auricles where the leaf blade meets the stem. The base of the stem often displays a reddish-purple color, and the leaves have a prominent, light-colored midvein.
Understanding the life cycle is essential for timing removal efforts. As a summer annual, it germinates when soil temperatures warm up, typically from mid-spring through early summer. Optimum germination temperatures range from 68 to 87°F. The plant rapidly produces tillers and vegetative growth, quickly entering its reproductive stage by forming dense, spiky seedheads (panicles) from July to September. Removal efforts must be timed before the plant sets seed, as this dramatically increases the soil seed bank for the following year.
Non-Chemical Strategies for Removal
For small infestations or where chemical use is not desired, physical and cultural methods offer effective non-chemical control. Manual removal (hand-pulling) is most successful when the plants are young seedlings and the soil is moist. Pulling mature plants is more difficult and can disturb the soil, potentially bringing new weed seeds to the surface.
Mowing can be employed as a cultural control, though it will not eradicate the weed. Barnyard grass does not tolerate low mowing heights for extended periods. Maintaining a frequent mowing schedule below three inches helps suppress the formation of viable seedheads. Always clean mowing equipment thoroughly after use, as it can spread seeds to new areas.
For garden beds, applying a thick layer of organic mulch, such as wood chips or straw, suppresses germination by keeping the soil cool and blocking light.
False Seedbed Technique
For larger, non-turf areas, the false seedbed technique manages the seed bank. This involves tilling the area to encourage a flush of weed germination. After seedlings emerge (typically one to two weeks), lightly cultivate or use a burndown product to eliminate the new growth before planting the desired crop.
Soil Solarization
Soil solarization is another technique where clear plastic sheeting is laid over moistened soil during the hottest months. This uses high temperatures to kill seeds and seedlings in the upper soil profile.
Effective Herbicide Treatments
Chemical control is often the most effective method for managing widespread or dense infestations. Treatments are categorized into pre-emergent and post-emergent herbicides, depending on the weed’s growth stage and environment. Pre-emergent herbicides prevent seeds from sprouting and must be applied before soil temperatures reach 62°F in the spring.
Pre-Emergent Herbicides
Common active ingredients include prodiamine, pendimethalin, and dithiopyr. These chemicals form a barrier in the soil that inhibits germination. Timing is critical; a late application will not prevent already germinated seeds from growing. In agricultural settings, residual herbicides containing Group 15 (e.g., S-metolachlor) or Group 13 (e.g., clomazone) are frequently used.
Post-Emergent Herbicides
Post-emergent herbicides are applied directly to the emerged plant and are most effective when the barnyard grass is young and actively growing. Selective products are necessary for use in lawns to avoid damaging the turfgrass. Active ingredients like fenoxaprop-p-ethyl, quinclorac, or topramezone are labeled for turf control. For spot-treating in non-turf areas, a non-selective herbicide like glyphosate can be used, but it will kill any plant it contacts. Using products with different modes of action is recommended to mitigate resistance development, as barnyard grass has evolved resistance to several herbicide groups.
Long-Term Prevention and Management
Long-term prevention is necessary to deplete the persistent seed bank. This involves altering the environment to create conditions unfavorable for barnyard grass germination and growth. Since this weed thrives in moist, disturbed, and poorly drained areas, improving soil drainage is a primary step.
Adjust irrigation practices to avoid frequent, shallow watering, which encourages surface germination. Deep, infrequent watering promotes robust root systems in desirable plants, making them more competitive. For turf, apply about one inch of water per week, all at once in the morning, to allow deep penetration and reduce surface moisture.
Enhancing turf density in lawn settings is effective, as a thick, healthy stand of grass will shade the soil and suppress emergence. This is achieved through regular fertilization and proper mowing heights. In agricultural or garden contexts, using narrow-row spacing or higher seeding rates establishes a dense canopy that shades the soil. Consistently preventing seed production, combined with the natural decay of seeds, will gradually reduce the existing seed bank.