GRASSES & SEDGES
GENERAL GUIDANCE FOR GRASSES AND GRASSLIKE PLANTS
A variety of methods are available for control of grasses, depending on the extent of the infestation, the type of habitat, and the availability of labor and other resources. Preventing the introduction of invasive grasses from infested to non-infested areas should always be a priority. Early control of new infestations will also reduce the likelihood of establishment and expansion. When deciding between physical and chemical methods, keep in mind that manual removal of plants can result in disturbance to the soil which can further encourage the invasive species and open the site up to new introductions. Using an herbicide leaves the plants and soil in place, thus minimizing that likelihood. The use of grass-specific herbicides will reduce impacts to non-target broadleaf plants.
Use pesticides wisely: always read the entire pesticide label carefully, follow all mixing and application instructions and wear all recommended personal protective gear and clothing. Contact your state department of agriculture for any additional pesticide use requirements, restrictions or recommendations. Notice: mention of a trade name does not constitute the endorsement of the product by authors, agencies or organizations involved in the production of this publication.
Biological control is not available for these species.
The following method is effective for control of most exotic invasive bamboos such as common bamboo (Bambusa vulgaris), golden bamboo (Phyllostachys aurea), arrow bamboo (Pseudosasa japonica) and others. It was developed by Dr. Francis Gouin, formerly the University of Maryland Agronomist and is presented here with slight modification.
Cut the bamboo down to the ground in spring (e.g., June). Depending on the type of bamboo you are working with, you will need a chain saw, weed whip or weed whacker, Swedish brush axe, pruning snips or other tool that will cut through the bamboo stems. Hand-held pruning snips work fine for the thinner stemmed running bamboos (Psuedosasa), but it is more labor intensive and time consuming. Cut down as low as is comfortable and leave alone for the summer, allowing it to regrow. In October or early November, on a sunny, non-breezy day, spray the leaves of regrown plants with a 2% rate of glyphosate (e.g., Accord® or Roundup Pro®), mixed with water, according to the label directions. Apply thoroughly just to the point of drip. Wait 10-14 days and reapply the glyphosate at the same rate. After the second treatment, leave the bamboo alone. Do not cut, mow, or remove plant material. The following spring, the bamboo will be browned out and should not grow back. At this point, you can cut and remove the dead vegetation. If any bamboo remains or does reappear, repeat the procedure.
See General Guidance.
Hand-pulling can be effective for young plants and light infestations.
For plants with established root mass, treat with a systemic herbicide such as glyphosate to kill the entire plant to the roots. Mature seeds may be present anytime from June through October, depending on local conditions. If present, clip and bag the seed heads. Power wash any equipment when moving between sites to remove seeds.
Biological control is not available at this time but is under active investigation. Finding an appropriate control agent for the U.S. is complicated by the co-occurrence of native and exotic genotypes.
Foliar. Systemic herbicides such as Accord®, Glypro® or Rodeo® and similar products containing 53-54% glyphosate, which moves through the plant to kill the roots, are most effective. Products must be labeled for wetland use. Low rates of herbicide (1.5-2%) mixed with water and a low toxicity surfactant approved for wetland use, can be applied to foliage using a backpack sprayer or power-driven hand sprayer. The most effective timing for treatments is after flowering into the fall, but applications can be made from June and early October as long as plants are actively growing and not under drought stress. Annual followup treatments should be made after July to allow for sufficient regrowth of plants affected by previous treatments and may be slower to emerge. For large infestations, truck-based applications or aerial treatments are the most practical and can be highly effective. The U.S. Fish and Wildlife Service, Chesapeake Bay Field Office, uses 1.25% glyphosate mixed with water and 0.625% surfactant (e.g., LI-700® made by UAP) from September through October applied to mature green plants. Treatments are followed with burning or mowing which helps the native vegetation recover. Another product to consider is Habitat® (imazapyr), which can be applied August-September in our region using 48-64 oz/acre (higher rate is best). To avoid damage to nontarget plants, maintain a 50-ft. buffer between the Phragmites and any desirable vegetation. Target vegetation in the buffer can be treated with glyphosate. Follow label precautions and avoid application to roots of desirable plants.
Cut-stem. Another method practical for small infestations is the following cut-stem treatment developed by The Nature Conservancy. Phragmites stems are cut at waist height for convenience for the applicator, cutting between the nodes to expose a hollow portion of the stem. Use a Nalgene® squirt bottle with a bent and pointed tip and fill with a 50:50 glyphosate and water mixture plus a blue marking dye to help track applications. Insert the tip into the stem and apply about ½ tsp. into the stem and around the cut edge. This can be done mid-summer through fall. Treated areas must be monitored and retreated as necessary for several years until the Phragmites has been eradicated.
Altering water levels can be an effective, non-chemical option for certain sites and conditions. For more information on this method, refer to The Nature Conservancy’s Element Stewardship report on Phragmites (see References).
Hand-pulling of plants is not feasible due to the extensive tough rhizomes.
Biological control is not available for this species, but pathogens have been observed infecting stiltgrass populations naturally.
For extensive stiltgrass infestations, use of a systemic herbicide such as glyphosate (e.g., Roundup Pro®) is a practical and effective method if used with some caution. Glyphosate is a non-specific herbicide that will kill or damage almost any herbaceous plant and possibly some woody plants it contacts. Roundup Pro® is surfactant-loaded (no additional surfactant needed) and the surfactant is not lethal to amphibians and aquatic invertebrates like the polyoxyethyleneamine surfactant in Roundup Classic® is. Roundup Pro® carries the ‘Caution’ signal word while Roundup Classic® carries ‘Warning’. When treating stiltgrass in wetland sites, use Rodeo® or other formulation labeled for wetlands. Apply a 0.5 to 1% solution of Roundup® or Rodeo® mixed with water (8 oz. per 3 gals. mix) and a surfactant in late summer. Be careful to avoid application to non-target plants.
Grass-specific herbicides (graminicides) such as sethoxydim and clethodim fluazifop-p-butyl work very well on stiltgrass and if used correctly can reduce potential damage to woody or broadleaf plants. Grass-out®, and Grass-B-Gon® are homeowner versions of these products. Some success has also been reported using pre-emergent herbicide imazapic applied in March in the Mid-Atlantic region. For more details on these methods, refer to the fact sheet on the Plant Conservation Alliance’s ‘Weeds Gone Wild’ website (see References).
Stiltgrass is a shallow-rooted annual that can be pulled by hand throughout the growing season, especially when the soil is moist and entire plants with roots can be removed. Pulling is easier and probably more effective in mid-to-late summer when the plants are much taller and more branched however if not done early enough, there’s a risk of plants flowering and producing seed. At this stage, entire plants can be easily removed by grabbing the basal portion of a plant and pulling firmly. In short time, a fair amount of stiltgrass can be pulled and piled up to dehydrate on site. If plants are already in the fruiting stage, they should be bagged and disposed of offsite to prevent dispersal of seed. Also, try to avoid pulling native grasses like Virginia cutgrass (Leersia virginica) that often grow intermingled with stiltgrass and may be difficult to distinguish from it. Because hand-pulling plants disturbs the soil and may expose stiltgrass seed from previous seasons, late season pulling will avoid the likelihood of survival of any seeds that germinate. Hand-pulling of plants needs to be repeated and continued for many seasons until the seed bank is exhausted. Stiltgrass can be mowed in late summer (i.e., August through September) when the plants are flowering but preferably before seed is produced. This can be done using a lawn mower or “weed whacker” type machine or a scythe. Because stiltgrass is an annual plant, cutting late in the season before the plants would die back naturally avoids the possibility of regrowth. Recent information suggests that stiltgrass plants that are cut early in the summer respond by regrowing and flowering soon after cutting, much earlier than they would normally flower. This is another reason to consider cutting in late summer to fall rather than during the early summer months.
Biological control is not available for this species.
In herbicide trials in Maryland, clethodim and glyphosate were effective. Clethodim is grass-selective, so it leaves behind the woodland wildflowers and the sedges. More detailed information on its use can be obtained from the Maryland Department of Natural Resources. In areas where basketgrass has formed a monoculture, a 1-2% solution of glyphosate (53.8%) mixed with water and a non-ionic surfactant can be applied using a backpack sprayer. The spray should be applied to wet the plants but not to the point of run-off. Applications should be made in a slow and careful manner to avoid harming or killing native plants. Prior to herbicide treatments, applicators must be taught to recognize native plants on site. It is important to control basketgrass before seed is produced and check each following year for results in June.
Where basketgrass is mixed with many native plants, manual removal of individual plants will help to retain the native flora. Plants can be pulled by hand fairly easily anytime. If not in flower, pulled material can be left on-site to desiccate and disintegrate. If plants are flowering and the possibility of seeds exists, it is best to bag and remove pulled material. However, once the awns become sticky it is probably best to stop pulling or working in basketgrass infestation because of the likelihood of spreading seeds.
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