By: Bonnie L. Grant, Certified Urban Agriculturist
Torpedograss (Panicum repens) is native to Asia and Africa and was introduced to North America as a forage crop. Now torpedograss weeds are among the most common and annoying pest plants here. It is a persistent plant that pierces soil with pointed rhizomes that grow a foot (0.3 m.) or more into the earth. Eliminating torpedograss in the lawn is a tricky business, requiring tenacity and usually multiple chemical applications. The weed is nearly indestructible and has been known to come out through weed barrier fabric.
The methods on how to get rid of torpedograss do not encompass selective herbicides or mechanical measures. This is bad news for those of us who prefer not to use chemicals on our landscape. You could just leave the stuff alone but it would first take over your lawn and then move to the garden beds.
Torpedograss weeds spread by their numerous seed but also from even tiny fragments of rhizome. This makes for a formidable foe and indicates the necessity of herbicide use as the primary torpedograss control.
The first step in any weed control is to correctly identify it. Torpedograss is a perennial that can grow up to 2.5 feet (0.7 m.) in height. It produces stiff stems with thick, rigid, flat or folded leaf blades. Stems are smooth but the leaves and sheaths are hairy. The color is grayish green. The inflorescence is a vertical loose panicle, 3 to 9 inches (7.5-23 cm.) long.
This annoying plant can flower all year long. The rhizomes are a key to torpedograss identification. They stab down into soil with pointed tips that spear soil and grow deeply. Any part of the rhizome that remains in soil will resprout and produce new plants.
Torpedograss control is nothing to jest about due to its difficulty and general unpredictability. As mentioned, weed barriers have little effect on the plant and hand pulling can leave behind rhizomes, causing more problems later.
There have been some studies showing burning as being effective but this is only in conjunction with herbicide use. In garden beds, use glyphosate applied directly to the weed. Do not get any of this non-selective chemical on your ornamental plants.
You may have to repeat again to ensure complete torpedograss control. You can also try a selective herbicide like fluazifop or sethoxydim. Repeated applications are again recommended. Both the latter chemicals will suppress torpedograss but likely not kill it.
The type of chemical you use in grass infestations will depend upon the species of grass growing in your lawn. Not all herbicides are safe on all types of sod. Kill patches of torpedograss in the lawn with glyphosate. It will take out a bit of the turf but you can remove the dead vegetation and reseed.
A kinder, gentler method in Bermuda grass or zoysia grass is to use a formula with quinclorac. In centipede turf, use sethoxydim. This will kill the torpedograss but not damage the lawn. Many other lawns have no recommended selective herbicide.
This article was last updated on
March 5 th : Torpedo Grass (Panicum repens) & Hydrilla (Hydrilla verticillata)
Torpedo Grass Photo Credit: Graves Lovell, Alabama Department of Conservation & Natural Resources, www.bugwood.org
Torpedo Grass: Torpedo grass (Panicum repens) is an invasive weed that invades lawns, flowerbeds, landscapes and wetlands. Even if introduced into a small area, this weed can rapidly spread to become a monoculture and crowd out native vegetation. Its name is derived from the hard, sharp point of the rhizome that looks like a torpedo.
Native to Africa and Asia, Torpedo Grass was introduced to the United States around 1876, primarily through seed used for forage crops. The real infestation came in the early part of the 20th century when the USDA imported and distributed seed for planting pastures as forage for cattle. It proved to be inferior for use as a forage crop. Now it is found in the Gulf South from Florida to Texas and in other coastal areas around the world.
Torpedo grass is nearly impossible to completely eliminate, so management of it is not a matter of how to get rid of it completely but instead how to prevent it from taking over an area. The only way that this can be accomplished is with repeated and frequent efforts. You will have to scout regularly and any time torpedo grass is seen, promptly take action. Prevention of torpedo grass centers on removal of the entire plant, as the plant can regrow from fragments left behind in the soil. There are few control options for torpedo grass. Options will depend on its location and surrounding vegetation. For management in lawns please refer to http://edis.ifas.ufl.edu/ep387 for specific herbicide controls based predominate lawn species. For management of invasive species in natural areas, refer to http://edis.ifas.ufl.edu/wg209 for a comprehensive list of species and their controls. As always, refer to instructions on herbicide label to ensure proper usage.
For more information contact the author Brooke Saari, Sea Grant Marine Science Extension Agent, 850-689-5850.
Hydrilla: Hydrilla is a perennial submerged plant that grows in dense mats up to the surface of freshwater habitats, including ponds, lakes, springs, and rivers. Growing at the rapid rate
Hydrilla Photo Credit: Vic Ramey, UF/IFAS Center for Aquatic and Invasive Plants.
of an inch a day and up to 25 feet long, hydrilla shades out beneficial native plants and clogs waterways, preventing flood control, boating, and fishing. In dense populations, the plant can alter oxygen levels and water chemistry and survive in a wide variety of nutrient conditions, sunlight availability, and temperatures.
Originating in Asia, it was introduced to Florida (likely through Tampa and Miami) in the 1950’s as part of the worldwide aquarium trade. Hydrilla has become a very expensive problem for the state. Millions are spent annually on chemical and mechanical treatment simply to maintain the plant. Adding to the problem is the fact that it is still available commercially, even though it has been placed on the US Federal Noxious Weed List. In the United States, the plant is found as far north as Connecticut and west to California and Washington.
Methods of control include mechanical harvesters and chopping machines (although fragments of hydrilla left in the water can regrow), introduced insects and fish (particularly the Chinese grass carp), aquatic herbicides, and lake drawdowns. Hydrilla is often transported from one body of water to the other by unknowing boaters moving fragments of the plant left on boats, trailers, or live wells, so learning to identify the plant and cleaning boats before leaving the ramp are helpful in prevention. Visit the Extension Hydrilla IPM site for more helpful tips.
For more information contact the author Carrie Stevenson, Coastal Sustainability Agent at 850-475-5230.
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If you want to kill monkey grass, herbicides with glyphosate can be quite effective. Glyphosate is a broad-spectrum herbicide and its application can kill normal grass and other plants too. You may need to use products like Roundup which contains glyphosate.
Rather than spraying on fully grown monkey grass, it is better to cut it first and then spray glyphosate. It may require two to three applications of glyphosate before you get rid of your monkey grass.
Applying Glyphosate is best done when the plants are actively growing. When using Roundup, apply it with a spray in a targeted manner to reduce the possibility of killing other plants.It is advisable to do the spraying or brushing on a sunny day.
Spray when there is not much wind to prevent the chemical from affecting other desirable plants.
However, you need to take adequate precautions while spraying glyphosate, such as wearing a mask, since this spray can cause eye irritation. Hence, avoid contact with eyes and clothing when you're using this chemical. As an extra precaution, you can also wear goggles when spraying.
After spraying, wash your hands thoroughly before having any food or drink.
Moreover, you should avoid using glyphosate when there are edible fruits or vegetables next to the monkey grass. Also, ensure that the pesticide does not get drained into the storm drains and other water bodies.
Please do not plan to apply the treatment when rain is forecasted in the next 24 hours.
Wire grass overtaking a stepping stone.
Our farm in North Carolina is infested with wire grass – and I do mean, infested! It’s growing in the fields it’s growing in the paths it’s tangling in the grapevines it’s everywhere! Next to the poison ivy, it’s probably the single most insidious weed we’ve got here.
Sometime back, I gave a cursory mention of wire grass in my article on How to Control Bermuda Grass, because, yes – botanically speaking – wire grass is an uncultivated form of Bermuda grass. But as someone who’s dealt with it in numerous yards in my life, I’m here to tell you that – metaphorically speaking – this stuff is the devil!
It grows right under garden edging. It grows right over landscape paper, mulch, gravel, sidewalks, and forgotten rakes. It even twines up into shrubs, where it reaches out to wave and laugh at you as you walk by. The roots are so deep that when you try to pull it, they break. And just when you think you’ve got wire grass under control, it releases seeds that fly into all the areas you just weeded. Remember my Weed-Proof Vegetable Garden? Well, it was – except for the wire grass.
When mowed, wire grass isn’t a bad looking lawn grass.
Back in the heyday of tobacco farming around here, farmers didn’t mess around with wire grass – they would patrol their hundred-acre fields and hand dig every tiny sprout. They wouldn’t dare allow even one patch to take hold.
It’s one of those weeds that doesn’t respond very well to “cultural practices,” meaning that if you want to be rid of it, you’re going to need an approach just one step shy of nuclear annihilation. Wire grass has to be tracked down and either completely killed or completely removed, and that’s likely to need doing more than once.
Like other forms of Bermuda grass, wire grass turns brown during the winter, so you can easily spot the telltale patches in a fescue or bluegrass lawn. If you’re planning to dig wire grass up, it’s best to do it while it’s brown and dormant. If you’re going to spray wire grass, take note of the patches in your lawn, then wait until it’s green and growing.
Here are some tips on controlling wire grass in your yard:
Once upon a time, I made peace with wire grass. At that time, I had a large fenced in backyard with four dogs running around in it, and the wire grass was the only thing that stood up to their energetic paws. As they trampled the regular lawn grass, the wire grass crept out into its place, so I fed it, watered it, mowed it, and everybody was happy. It’s not a bad looking grass if you can keep it out of your flower beds.
And I must confess that I didn’t pull it out of my vegetable garden this year. With the garden completely surrounded by wire grass, it seemed like a losing battle. And for all my preaching, I’m really not much of a weeder either. The veggie plants did just fine, though by summer’s end the garden was a bit of a tangle!
Wire grass is one of those plants that you can either live with or fight with. But if you’re willing to take an aggressive approach and stick with it, it’s possible to keep wire grass at bay.
Glyphosphate: (such as Roundup) is considered the most effective herbicide against torpedo grass, though it kills lawn grass and other plants, too. Protect Waterways: Torpedo grass often grows near and in water. Never use herbicides if the spray can come into contact with waterways.
Similarly, does vinegar kill Zoysia grass? Zoysia is a very tough grass, which is great in warm climates, as it grows so thick that it prevents the growth of weeds, and because it also grows more sideways than up, it requires less mowing. If boiling water does not work, you can kill it using a propane torch to burn it. Vinegar has also enjoyed good success.
Simply so, does Atrazine kill torpedo grass?
No herbicides can selectively control torpedograss, bermudagrass and most other grassy weed in St. Augustinegrass. You can kill patches of grassy weeds that grow in summer with glyphosate (keep this off the desirable grass as much as possible).
How do I get rid of rhizomes in my lawn?
Because it's so tough and persistent, most professionals and homeowners use an herbicide (generally glyphosate) to kill it. They spray, strip off the dying sod, irrigate to generate growth of any surviving rhizomes, and then repeat the process at least once (one treatment rarely kills a Bermuda lawn).
Common bermudagrass is the most widespread grass problem infesting flowerbeds.
Bushkiller vine. (Photos by Ron Strahan)
Chamberbitter is an extremely invasive summer annual.
Purple nutsedge is the most common weed infesting residential and commercial landscape plantings.
Louisianians take pride in the appearance of their landscapes, and weeds detract from this beauty. Along with being aesthetically displeasing, weeds in flower beds compete with desirable plants for water, nutrients and light and soon can get out of control.
Most people rely on back-breaking hand removal to remove weed problems. Hand pulling may be successful for a few weeds, but for most it is only partially effective. Weeds have defense mechanisms that reduce the effectiveness of hand pulling. Annual weeds often break at the stem when pulled, leaving the root or single stem available for potential reestablishment. However, for perennial weeds like purple nutsedge and bermudagrass hand removal is nearly impossible. Perennial weeds have underground structures that are left in the soil after hand removal.
In reality, hand pulling weeds is one of several practices that should be used together for optimum weed control in flowerbeds. These additional practices include the use of mulch, preemergence herbicides and, to a limited extent, postemergence herbicides.
Mulch is an extremely important tool for weed management in landscape beds. Mulch acts as a physical barrier to the emerging seedling, and it prevents sunlight from reaching the soil surface. Blocking sunlight is important because some weed seeds such as crabgrass will not germinate without stimulation from sunlight. Also, sunlight is critical for the new weed seedling to begin photosynthesis for growth and development.
Several materials are suitable for mulch including, compost, leaf litter, pine bark, pine mulch and pine straw. Even newspapers can be used as a barrier to weed emergence. Mulches must be thick enough to block light to be effective. As a rule, mulch trees to a depth of 3-4 inches and shrubs to a depth of 2-3 inches. Though mulch is beneficial, it will not hold back most weed infestations. It is important to use mulch in conjunction with preemergence herbicides.
Using herbicides for flowerbed weed control can be difficult because of the wide array of high-value ornamental plants grown and their varying tolerances to herbicides. When it comes to herbicide use in flowerbeds, ornamentals are most tolerant of preemergence herbicides.
Preemergence herbicides are weed preventers that are used in most every row crop to supplement a bevy of postemergence herbicide choices. However, these types of herbicides are almost exclusively relied upon for flowerbed weed management and are the backbone of chemical weed control in landscape beds. Preemergence herbicides work by forming a barrier in the upper ½ to 1 inch of the mulch or soil where most seeds germinate and kill weeds as they attempt to emerge.
Because these herbicides have no effect on existing weeds, timing the preemergence herbicide application properly is critical for success. Because they work prior to weed emergence, applications must occur before weed germination. Any existing weeds should be hand removed or carefully spot-treated with a nonselective herbicide prior to treatment. Add water after applying the herbicide. In most cases preemergence herbicides should be applied every 2½ to 3 months. Consult product labels concerning tolerances by desirable plants.
Preemergence herbicides can be effective on several annual weeds including crabgrass, goosegrass, spurges, common purslane and mulberry weed. Most perennial weeds such as purple nutsedge and Florida betony are not controlled with preemergence herbicides.
It is important to control weeds with mulch and preemergence herbicides because once they have emerged your options become more limited. Few selective postemergence herbicides are available, especially for broadleaf weeds. There is good news when it comes to selectively controlling most summer grasses like crabgrass and bermudagrass and sedges like purple and yellow nutsedge. Most summer grasses are controlled with herbicides containing the active ingredients fluazifop or sethoxydim. Sedges can be controlled by directed sprays of halosulfuron (Sedgehammer) or sulfosulfuron (Certainty). Additionally, glyphosate can be carefully spot-treated or applied as a wipe for hard-to-control weeds.
Common weeds infesting flowerbeds
Spurge – Several types of spurges are common in landscape beds. Members of the Euphorbaceae (poinsettia) family, spurges are prolific seed-producing annuals that thrive in hot weather. Under optimum growing conditions, plants can go from seed to flower in only three weeks. Some spurges have a more prostrate growth habit that can form dense mats, whereas many spurge species grow more upright. Spurges emit milky latex from broken stems that can be helpful in distinguishing this plant from other species. The plants are difficult to manage in flowerbeds due to heavy seed production and the inability to be successfully removed by hand. Plants often break at the stem during this process, leaving the root and several buds or a single stem available for potential reestablishment.
Control: Most preemergence herbicides work well on spurge. However, the problem usually is in the frequency of the application because spurge control starts failing four to six weeks after application. Professional herbicides that work well include Free Hand (dimethenamid + pendimethalin), Pendulum/PreM and other trade names (pendimethalin), Barricade and Regalkade (prodiamine), Surflan (oryzalin) and Snapshot (isoxaben + trifluralin). Consumer herbicide options include Preen (dithiopyr or trifluralin) and Amaze (benefin + oryzalin).
Chamberbitter (Phyllanthus urinaria) – A member of the Euphorbiaceae family, chamberbitter is an extremely invasive summer annual. Chamberbitter resembles hemp sesbania or mimosa seedlings. However, the most distinguishing characteristic is the round seed capsules located on the underside of slender branches. Chamberbitter needs temperatures consistently above 75 degrees therefore, these plants tend to germinate a little later in the spring than many other flowerbed weeds. Populations of chamberbitter have increased significantly since their introduction from Asia because of their prolific seed production and tolerance of most preemergence herbicides labeled for use in ornamental nurseries.
Control: Light may be necessary to stimulate chamberbitter germination, so thick mulch is helpful in reducing plant populations. Chamberbitter hand pulls very easily, but frequent germination and high populations make hand removal only partially effective. Preemergence herbicides have performed erratically, so using hand removal and mulch in conjunction with herbicides are important to optimize chamberbitter control. Professional herbicides that have activity on chamberbitter include Rout (oxyfluorfen + oryzalin), OH2 (oxyfluorfen + pendimethalin), and other oxyfluorfen containing herbicides. Sureguard and Broadstar (flumioxazin) are effective herbicides as well. Most consumer herbicides are weak on chamberbitter. However, Amaze (benefin+ oryzalin) provides partial control.
Common bermudagrass – Common bermudagrass is the most widespread grass problem infesting flowerbeds. It is a perennial, warm-season grass originating in Africa that grows well in our Louisiana climate. The grass is widely used for lawns, athletic fields and golf courses, but it is invasive in flowerbeds. Common bermudagrass is characterized by its dark green color, fine texture and the production of rhizomes (below-ground stems) and stolons (above-ground stems) that allow the plant to establish quickly in the landscape.
Control: Because of its complex stolon and rhizome system, hand removal is not effective for controlling common bermudagrass infestations in landscape beds. Because the weed mainly reproduces vegetatively and creeps into flowerbeds, preemergence herbicides have no effect on the weed either. Frequent applications of grass-killing herbicides like Fusilade and Segment can be effective in managing bermudagrass in landscape beds. These types of herbicides only work on grasses and are usually safe over the top of most nongrass landscape plants such as bedding plants, perennial ground covers and shrubs. Consumer versions of these herbicides include Ortho GrassBGon (fluazifop) and Fertilome Over the Top II (sethoxydim).
Nutsedges – Purple nutsedge ranks as the No. 1 weed problem in the world and is the most common weed infesting residential and commercial landscape plantings. Yellow nutsedge prefers moist environments and is more common in irrigated beds or during wet growing seasons. Both are grass-like plants with an extensive system of tubers that allow the plants to reproduce rapidly in landscape beds.
Control: Nutsedges are difficult to manage consistently in landscape beds. Neither purple nor yellow nutsedge can be controlled by hand removal, and mulches are only slightly effective. Yellow nutsedge can be partially managed with preemergence herbicides with the active ingredients metolachlor (Pennant Magnum) or dimethenamid (Tower and Free Hand). Unfortunately, there are no good preemergence options for purple nutsedge.
Postemergence herbicides Sedgehammer (halosulfuron) and Certainty (sulfosulfuron) are two effective herbicides registered for the selective removal of sedges in landscape beds. In most situations, these herbicides should be applied as directed sprays. Consult product labels for lists of tolerant plants and application techniques. For most situations, the best defense against weed infestations in the flowerbed is reliance on mulch, periodic hand pulling and an aggressive preemergence herbicide program.
Certain weeds prevalent in Louisiana landscapes are almost uncontrollable.These include torpedograss, bushkiller vine and cogongrass.
Torpedograss – Torpedograss is a perennial, rhizomatous grass that is considered one of the most invasive grasses in the world. Although the plant does produce seed, the seeds are not viable. The weedy grass solely reproduces vegetatively by robust rhizomes. The spread of torpedograss in Louisiana is mainly attributed to the movement of soils infested with torpedograss from the Bonnet Carré Spillway. The spillway is just west of New Orleans and is the main source of torpedograss for southeast Louisiana, especially within the New Orleans metro area. For years, there were no reports of infestations in north Louisiana however, torpedograss infestations have been confirmed at several locations in northern areas of the state.
Control: Complete control of torpedograss may not be possible. Grass-killing herbicides normally prescribed for flowerbeds like sethoxydim and fluazifop are just not very effective on torpedograss, although fluazifop is a little better than sethoxydim. Glyphosate is the best herbicide on the weed, but high rates are necessary for control. Directed sprays of glyphosate are not always safe in landscape plantings due to the potential for drift. It may be safer to wipe the weed with a glyphosate/water solution that is at least 10 percent glyphosate when it is in a landscape bed. Using a chemical-resistant glove inside a cotton glove to wipe the solution on the torpedograss foliage is an effective method of application. Repeated applications are always necessary for torpedograss.
Bushkiller vine – This perennial herbaceous vine has compound leaves containing five leaflets. It produces salmon colored flowers eventually producing fruit with two to four seeds. Thankfully, the seed are not thought to be viable. The plant solely reproduces vegetatively. Native to Asia, bushkiller gets its name because the vine climbs over desirable plants and kills other plants by blocking out sunlight. Few weeds take over areas as fast as bushkiller vine, and it rapidly overtakes landscape shrubs and groundcovers.
Control: Bushkiller vine can be suppressed with repeated applications of two herbicides, glyphosate and triclopyr, applied as directed sprays. Unfortunately, the vine intertwines in the landscape, making herbicide applications very difficult. Often it is necessary to treat fresh-cut plants or wipe the weed directly when spraying is too risky in the landscape. Don’t expect to get rid of it with one application. Be sure to treat properties nearby because the weed will rapidly re-infest treated areas.
Cogongrass – Cogongrass has been causing problems in the southeastern areas of the United States for several years. Thousands of acres are covered with the perennial grass, and millions of dollars have been spent to control this invasive weed. In Louisiana, St. Tammany Parish has the highest population of cogongrass, another 10 parishes may have some degree of infestation. Cogongrass is native to Southeast Asia and spreads by both wind-blown seeds and underground, creeping rhizomes. The plant produces fluffy, white, plume-like seed heads in early spring. Cogongrass makes about 3,000 seeds per plant, but the seeds need to land on bare soil to get the weed established. The main way the plant gets established is by rhizomes either transported on tillage equipment, through contaminated soil or by creeping into new areas. Rhizomes may make up 80 percent of the plant mass, which allows the plant to recover from most mowing and herbicide applications. Once the cogongrass is established, the area becomes a monoculture of cogongrass with nothing else able to grow.
Control: Cogongrass control is a long-term endeavor that requires the repeated use of glyphosate and imazapyr (Arsenal). Areas treated must be taken out of use potentially for years. This weed problem requires landscapers no option but to declare an all-out war to reclaim the land.
Ron Strahan, Associate Professor, School of Plant, Environmental & Soil Sciences, LSU AgCenter, Baton Rouge, La.
(This article was published in the winter 2012 issue of Louisiana Agriculture magazine.)