Eriochloa villosa (Thunb.) Kunth - Woolly Cup Grass

Cyperales: Poaceae

Identification
Context
Geographical Distribution
Habitat
Field Recognition/Morphology
Biology/Life Cycle
Dispersal
Environmental Impacts
Economical Impacts
Control/Management
Reporting
Figures
Additional Web Links
References

Identification

Name: Eriochloa villosa (Thunb.) Kunth

Synonyms: Helopus villosus (Thunb.) Nees. ex Steud.; Paspalum distichum Houtt. (non L.) (Shaw and Webster, 1987); Paspalum villosum Thunb. [basionym] (USDA, ARS, 2004; Darbyshire et al., 2003).

Common names (E): Woolly cup grass, woolly cupgrass, hairy cupgrass, Chinese cupgrass (Darbyshire et al., 2003).

Common names (F): Ériochloé velue (Darbyshire et al., 2003).

Context

Woolly cup grass is a tall annual grass of the millet tribe. In North America, it is a summer annual weed of agronomic crops. It occurs mainly in the northern corn belt of the United States, in Illinois, Iowa, Minnesota, and Wisconsin where it is a weed of economic concern in corn and soybeans. In Canada, it has been reported in a number of sites in Quebec, and these sites are subject to phytosanitary measures.

The Canadian Food Inspection Agency (CFIA) initiated a Pest Risk Analysis in 2002 to assess the cost-effectiveness of requiring phytosanitary measures for controlling further introductions of woolly cup grass in Canada. This would be done under the authority of the Plant Protection Act. As a result of this analysis, and after consultations, the CFIA has decided to regulate woolly cup grass. Regulatory measures are now underway.

The Plant Protection Act and the Plant Protection Regulations provide the legislative authority to prevent the importation, exportation and spread of pests injurious to plants.

Woolly cup grass is regulated under the Seeds Act and Regulations. The Seeds Act provides authority covering the testing, inspection, quality and sale of seeds in Canada. Woolly cup grass is listed as a Class 1 Prohibited Noxious Weed Seed under the Weed Seeds Order, 2005. Its presence as a contaminant in domestic and imported seed is prohibited (Section 4(2), Seeds Act).

Acts and regulations we enforce include:

Geographical Distribution

Asia: Native in temperate and subtropical Asia; occurs in China, Japan, North and South Korea, Mongolia, Russia, Taiwan and Indochina (Yong, 1966; Hsu, 1975; Tsvelev, 1984; Koyama, 1987; Shaw and Webster, 1987; Darbyshire et al., 2003).

United States: Introduced in the United States; reported from California, Colorado, Illinois, Iowa, Kansas, Minnesota, Mississippi, Missouri, Nebraska, Oregon, Pennsylvania, and Wisconsin (Darbyshire et al., 2003; USDA, ARS, 2004). Reports from Florida appear to be based on cultivated material (Darbyshire et al., 2003).

Canada: Introduced in Québec (a number of sites are under monitoring by ministère de l'Agriculture, des Pêcheries et de l'Alimentation (MAPAQ) and CFIA). Woolly cup grass is not otherwise known in Canada, but has the potential to become a serious problem, particularly in the corn and soybean production areas of southern Ontario and Quebec.

Habitat

In its native range, woolly cup grass is reported to be a weed of rice fields (Tsvelev, 1984). It also occupies open grassy places (Koyama, 1987), hillsides (Hsu, 1975), roadsides and wasteland (Yong, 1966). In the United States, woolly cup grass is a weed of cultivated fields and other areas with disturbed soil (Allison and Darbyshire, 2001). It seems best adapted to corn-corn or corn-soybean crop rotations (Owen, 1990), which are grown primarily in the midwest corn belt (Figure 1). The diversity of habitats in which woolly cup grass is found (e.g. from the boreal region of eastern Russia to subtropical areas of Taiwan and California, Oregon and the northern Great Plains of North America) indicates that it is adapted to a wide variety of climatic conditions and is successful as a weed in temperate climates. "There is no evidence that it is limited by the climatic conditions in areas of agricultural production in southern Canada" (Darbyshire et al., 2003).

Field Recognition/Morphology

Woolly cup grass is a tall grass, with reported heights that range from 30-200 cm (Strand and Miller,1980; Koyama, 1987; Allison and Darbyshire, 2001) (Figure 2). Leaves are dark green in colour and wider than those of most other grass seedlings (Figure 3), including foxtails (Setaria spp.). They are densely hairy on both blades and sheaths which gives them a velvety feel (Strand and Miller,1980) (Figure 4). Only one edge of the leaf blade is typically crinkled (Mickelson et al., 2000) (Figure 5). There are no auricles but the ligule is present as a fringe of fine hairs (Strand and Miller, 1980; Koyama, 1987) (Figure 6). Stems are nodose, smooth and without hairs except at the tip, and at the inflorescence axis (Koyama, 1987) (Figure 7).

Flowers are borne in terminal panicles with 3-9 raceme-like branches extending out from one side, measuring between 4-7 cm in length (Figure 8). The central axis of the panicle, the racemes, and the pedicels of the spikelets are very woolly. Each raceme bears many spikelets in two rows on the lower side and has a single apical spikelet at the tip (Strand and Miller,1980; Koyama, 1987) (Figure 9).

Seeds are ovate-elliptic in shape, and are relatively large, measuring about 4.5-5 mm in length and 2-3 mm in width. They range in colour from light green to tan depending on maturity, and may also have varying amounts of purple when mature (Figure 10 and 11).

Similar species: Foxtails (Setaria spp.), Paspalum spp., Digitaria spp., Barnyard grass (Echinochloa crus-galli). Woolly cup grass can be distinguished by its wider leaf blades, its terminal panicles with raceme-like branches and its characteristic spikelets with their cup-like callus at the base (Figure 10) (Strand and Miller, 1980; Allison and Darbyshire, 2001).

Biology/Life Cycle

Woolly cup grass is an annual that reproduces by seed, so that only seeds need survive the winter. Woolly cup grass tends to emerge earlier than other grass weeds in the U.S., usually within the first month after planting of the crop (e.g. April-May). The species is also characterized by repeated germination events over the course of the growing season (Owen, 1990), and a small percentage of seeds in the seed bank may continue to emerge throughout June and into July (Hartzler et al., 1999; Mickelson and Harvey, 1999a). Plant growth is rapid (Rabaey and Harvey 1997) and seedlings initiate tillering at the two or three leaf stage (Owen, 1990; Mickelson and Harvey, 1999b; Bello et al., 2000). A single plant is capable of producing up to 164,000 seeds in a season under ideal conditions, some of which will germinate the following spring and some of which will enter the seed bank (Owen, 1990).

While woolly cup grass shows aggressive emergence in the first year, it appears to form less persistent seed banks than some other important weed species (Buhler and Hartzler, 2001). The seeds can germinate over a broad range of soil depths and temperatures (Owen, 1990; Bello et al., 2000); this flexibility provides a competitive edge to the specie (Owen, 1990).

Woolly cup grass plants use the C₄ photosynthetic pathway (Shaw and Smeins, 1981; Clayton and Renvoize, 1986).

Dispersal

Mechanisms for natural seed dispersal are not known, and it is assumed that seeds generally fall close to the parent plant or travel short distances on the wind. Species in the genus Eriochloa do not seem to have specialized dispersal structures (Darbyshire et al., 2003).

The most important long-distance dispersal method for woolly cup grass is human transportation. Contaminated farm machinery is considered the most common source of new infestations in the United States (Hartzler, 1996). The success of this dispersal method is illustrated by the extensive spread of woolly cup grass in the U.S. since its introduction in the 1940s.

Environmental Impacts

There is no evidence that woolly cup grass has direct impacts on natural ecosystems or native species in its introduced range in the United States. It appears to be primarily limited to agricultural areas, and specifically to the corn belt in the Midwest. Woolly cup grass is most likely to affect the environment indirectly, through the impacts of increased tillage and herbicides used in control programs.

Economical Impacts

The primary economic impacts of woolly cup grass are reduced crop yield caused by competition with corn and soybeans (Tapia et al., 1997), and increased cost of control (Owen, 1990). Impacts are more pronounced in corn than in soybeans, as woolly cup grass is most competitive with annual crops of similar growth habit. Weed control is a standard component of any crop production system, but woolly cup grass is more difficult to control than many other grass weeds (Owen, 1990).

Woolly cup grass is a difficult weed to control. Its management might require increased herbicide use combined with other methods such as sanitation, cultivation, and crop rotation. Woolly cup grass seeds germinate throughout the growing season and commonly used pre-emergence herbicides do not provide adequate weed control. Moderate to heavy woolly cup grass infestations would require a second post-emergent herbicide application (Mickelson et al., 2000). The additional cost would be between CAN$44 and CAN$59 per hectare, including application work. In Canada in 2007, corn was cultivated on 1.65 million hectares (Statistics Canada, 2007).

Control/Management

Woolly cup grass is extremely difficult to manage in agricultural systems (Owen, 1990). No single strategy will provide consistent control, and individual producers must develop programs to fit their specific conditions and cropping systems. In general, management recommendations include sequential herbicide applications combined with sanitation and cultural and mechanical strategies such as, crop rotation and cultivation. When the eradication is the final objective, it must be kept in mind that one single plant is able to produce seeds, which will feed the seed bank and reintroduce the weed for several years.

Sanitation:

To prevent the woolly cup grass from becoming established in new areas is the easiest way to control it. Recommendations include:

Clean machinery when moving between fields
Till and harvest in infested fields in last
Prevent woolly cup grass from growing in adjacent waterways, fencerows and terraces
Use certified seed, which must be free of woolly cup grass seeds.

Chemical control:

The woolly cup grass is tolerant to several herbicides commonly used in corn and soybean production.

Woolly cup grass shows an excellent response to glyphosate, even late in season (Mickelson et al., 2000).
Pre-emergence herbicides alone do not provide adequate weed control. Plants that emerge after an application of a nonresidual post emergence herbicide, will not be controlled (Mickelson et al., 2000).
In corn and soybeans: in general, it seems that herbicide control is easier to achieve in soybeans and more difficult in corn. Apply sequential herbicide treatments combining pre- and post- emergence herbicides (for more details see: Mickelson et al., 2000; Owen, 1990; Hartlzer, 1996; Rabaey et al., 1996, Rabeay and Harvey, 1997; Darbyshire et al., 2003).
Reduce woolly cup grass seed production by controlling late-emerging plants (Mickelson and Harvey, 1999a and 1999b).

Cultural / Mechanical control / Crop rotation:

A rotation of small grains or forage crops, omitting full-season annual crops for more than one year, might be used (Owen, 1990; Hartzler, 1996). However, even though alfalfa is competitive against the weed (Mickelson et al. 2000), woolly cup grass is able to persist and produce seeds (Néron, 2007 personal communication).
Rotary hoeing after woolly cup grass has germinated but before emergence or cultivation (preferably shallow) when weeds are small. Several trips with hoe or cultivator may be necessary (Owen, 1990).
Later in the season, easy rooting at the nodes confers resistance to mechanical control methods since cutting or breaking the main stems does not kill the flowering branches (Néron, 2006, personal communication).

Biological control:

No reports found.

Reporting

Reporting this invasive plant in Canada should be done through your local CFIA office. For a list of offices, please call 1-800-442-2342 or consult the list of regional offices online.