Goosegrass is an annual grassy weed that has been a perennial pest for sports turf managers. In the turf care industry, there are two groups of weeds, generally characterized by difficulty of control. Sure, there are annual grasses, annual broadleaves, perennial grasses, perennial broadleaves, biennials and even those that really don’t fit into any of these, such as the sedges. Perhaps the best way to classify them, at least in a practical sense, is that there is an easy-to-control group of weeds and there is a hard-to-control group. As you probably know, goosegrass falls into the hard-to-control group.
- Goosegrass has many distinct features that make it relatively easy to identify.
- It has dark green leaves that grow on stems that become white toward the base.
- The leaf blades are folded in the bud, about .25 inches wide and taper to a point.
- The ligule is membranous, toothed and divided at the midrib. Generally, goosegrass is devoid of auricles.
- The sheath is light green on the upper parts and becomes white at the base. The sheath is flattened, with a few long, white hairs near the collar.
- The root system is shallow and fibrous.
- The seedhead is divided into finger-like segments, but thicker and more robust than crabgrass. The segments are often described as “zipper like.” If not mowed, seedheads grow to be 4 to 8 inches long.
Even as a mature plant, goosegrass appears flattened.
PHOTO BY JOHN FECH, UNL.
Life cycle and growth habit
- Goosegrass germinates in late spring, when soils have warmed and the soil temperature is consistently in the 60 to 65-degree range. Germination may continue all season until temperatures cool in the fall. This characteristic can come in handy when developing a plan for control.
- The stems of goosegrass are thick and grow low to the ground. These prostrate stems have several basal tillers that radiate from a common growing point. This low-growing habit allows it to persist and thrive under low heights of cut, as the majority of the leaf tissue remains after mowing. One of the most effective control methods of weed control is mowing, which works quite well for weeds like shepherd’s purse that have an upright growing habit, but not so well for goosegrass and prostrate knotweed.
Capacity to grow in compacted soils
- Like prostrate knotweed, goosegrass has the capacity to germinate and grow well in heavily compacted soils, even when the soil particles are smashed together so tight that you’d think it was an area being prepped for pouring concrete. The growth habit and the structure of goosegrass are features that allow it to grow well on football, baseball and soccer fields. Most weeds favor open, thin turfs. Goosegrass is no exception. Due to divots, diseases, insects and other injuries, fields are sometimes not as thick as desirable.
- As a result of intense sports play, the soil on most fields, or at least certain portions such as goalmouths and between the 20-yard lines, tends to be compaction-prone. Plants with a shallow, fibrous root system, such as goosegrass, can tolerate compacted soils. There is no evidence that goosegrass prefers compacted soils, rather that it simply outcompetes other plants when soil particles are excessively compressed. It has been speculated that plants like goosegrass have a competitive advantage in compacted soils because they can tolerate lower oxygen levels. Another consideration is that because compaction and wear occur concurrently in high-use areas, it is difficult to determine which is more problematic. Each can be damaging on their own, as well as the combination of the two. Clear research procedures are needed to examine their separate effects. Arguing the point may be of academic interest, but loses practicality in the real world.
- Integrated pest management (IPM) techniques are helpful when it comes to controlling weed species in the easy-to-control group, such as dandelion and plantain. Mowing height, for example, is particularly effective at reducing the population of crabgrass. When possible, mowing an inch or 2 higher will produce a canopy of plant tissue that shades the soil, making the soil surface less conducive for crabgrass germination.
- Most IPM techniques are generally not as effective for weeds in the hard-to-control group, including goosegrass. The following practices will provide benefits and a more competitive growing environment for desirable turfgrasses. In general, turf management practices that reduce soil compaction and excess soil moisture and maintain healthy turf will minimize goosegrass infestation.
- Fertilization: Turfgrass species such as bermudagrass and perennial rye are relatively rapid-growing grasses, and respond favorably to increased fertilization. One pound of nitrogen per 1,000 square feet per growing month helps regrow the turf canopy in areas damaged by traffic. Of course, these nitrogen rates can produce the negative side effect of encouraging succulent tissue, which tends to be more susceptible to foliar diseases such as leaf spot; keep this in mind as you increase turf fertility in an attempt to control goosegrass.
- Irrigation: Adequate to excessive moisture in the upper inch of soil is required for the germination of goosegrass. Reductions in the frequency and amount of irrigation water can limit germination; however, because the root systems of desirable turfs are also shallow, there is a fine line between creating a soil medium that is too dry for goosegrass germination, yet supports the vigorous growth of turf. In all situations, uniform irrigation distribution should be achieved to avoid having areas that are too dry or too wet.
- Compaction/wear: The areas where goosegrass is most commonly located on sports fields are exposed to frequent shearing from athletes as well as occasional vehicular and foot traffic, which results in soil compaction and wear of the turf. Core aeration will alleviate compaction if performed on a regular basis. In some parts of a field, turf wear can be decreased by diffusing and avoiding traffic, especially after rainfall.
- Timing of seeding in spring: Because perennial ryegrass will germinate at a cooler temperature than goosegrass, a short window exists in the spring to allow establishment of desirable turf before goosegrass is favored. This is a tricky technique to use, as both species are encouraged by moist growing conditions. Depending on the season, priming and pregermination techniques combined with early seeding of desirable turfgrasses may prove to be successful. Seeding of cool-season grasses after soil temperatures consistently reach the 60 to 65-degree range should be avoided in areas with a history of goosegrass infestation.
- Physical/mechanical removal: Hand-weeding, where roots are cut below the ground to avoid disturbance of the surface appearance, can be utilized on special occasions, such as before important games. Though not practical for large areas, it is useful in controlling mature goosegrass plants, and might be a more likely option if you have a ready source of seasonal labor
- Preemergence options: Many preemergence herbicide products are labeled for the control of goosegrass. The key to success, however, is timing. As previously mentioned, goosegrass is not an early-season germinating species. Applications of herbicides such as pendimethalin (several), dithiopyr (Dimension) or prodiamine (Barricade) made in early spring are not as likely to provide adequate control compared to ones timed to soil temperatures. Test soil at various depths and locations in the field to determine the actual temperature in the rootzone. These readings should be taken daily in the spring; endeavor to do so at the same time each day for consistency.
- Postemergence options: MSMA has been an option for sports turf managers in the past, but as of January 1, 2011, the EPA removed it from the marketplace. As with most product removals, existing inventories can be used according to label directions. Fortunately, several other options are available, including fluaziflop (Fusilade II), mesotrione (Tenacity), sulfentrazone (Dismiss) and foramsulfuron (Revolver).
Goosegrass plants that are not suppressed by a thick turf stand or preemergence herbicide application can be controlled with post- emergence herbicides. Often referred to as “escapes,” these weeds can sometimes blend with the desirable turf, especially when young. As Dr. Bobby Walls, product development manager for FMC Professional Solutions, suggests, “Young goosegrass is difficult to see in a dense turfgrass canopy. By the time it is large enough to see, goose- grass has progressed to the one to four-tiller stage.”
A study conducted by Dr. Fred Yelverton, extension specialist at North Carolina State University, evaluated Dismiss turf herbicide applied alone and in combinations for goosegrass control at the one- to four-tiller stage. Best results were achieved with a postemergence combination of Dismiss at the 8-ounce-per-acre rate and Revolver at the 17-ounce-per-acre rate.
As with any pest control agent, be sure to read and follow the pesticide label thoroughly. Take special note of tolerant species; reapplication guidelines; instructions on whether to follow the herbicide application with irrigation water; the need for additives, such as surfactants or crop oil concentrates; re-entry restrictions; pH of tank mix water; and the rates for effective control.