Brent Sellers and Pratap Devkota
Weeds in pastures and rangeland cost ranchers more than $180 million annually in Florida by reducing forage yield, lowering forage quality, and causing animal injury through toxicity or specialized plant organs (thorns and spines). Effective weed management begins with a healthy pasture. Weeds are seldom a serious problem in a well-managed, vigorously growing pasture. Good pasture management involves the proper choice of the forage species and variety, an adequate fertility program, controlled grazing management, and pest management (weeds, insects, and diseases). This publication provides practical pasture and rangeland weed management information for landowners, Extension agents, state and federal agency personnel, and others interested in managing grazing lands in Florida.
If pasture health declines, weeds will become established. Unless the management problem that caused forage decline is corrected, the grass will not reestablish and weeds will continue to re-infest the area. Bare ground is the perfect environment for establishment of weeds. Once established, weeds must be effectively controlled with mechanical or chemical methods.
Integrated weed management is both an economically and environmentally sound approach to weed management. An integrated approach involves scouting, prevention, and control (biological, cultural, mechanical, and chemical) in a coordinated plan.
Scouting
Scouting pastures periodically, which is often overlooked, is the foundation of a sound weed management program. Scouting involves routinely walking or driving through pastures and identifying a weeds issue. This defines the scope of the problem and allows the best management practices to be implemented in a timely fashion. The number of weeds, the species present, and their locations are important. Note the dominant species as well as uncommon or perennial weeds. The management strategies adopted should focus on controlling the dominant species while preventing the spread of less common species. If not managed proactively, the less common weeds in a pasture may become dominant weed problems.
Proper identification of weeds is the first step toward weed control. A good example is knowing the difference between tropical soda apple (TSA) and red soda apple (cockroach berry). Of the two, only TSA is a troublesome invasive weed. However, these two species can be incorrectly identified. This costly mistake allows TSA to go uncontrolled and results in the weed spreading throughout the ranch and potentially onto neighboring ranches. If you have questions about weed identification, contact your local UF/IFAS Extension office for assistance.
Some weeds grow best in wet sites (maidencane ponds, depressional areas, ditches, etc.) while others can be found on dry sites (ditch banks, upland areas, and fencerows). Scout pastures for weeds in conjunction with other activities, such as checking calves, working cattle, and feeding. When you first discover a weed, remove it or spot treat with an appropriate herbicide. Do not allow that one plant to produce seeds and give rise to hundreds of new plants. It is less costly in terms of both time and money to control one plant than to wait and have to control hundreds of plants.
Poisonous plants (e.g., Crotalaria, black nightshade, spiny pigweed, lantana, etc.) are commonly found throughout Florida. Animals do not usually choose to graze most poisonous plants when forage is abundant; however, when quality forage is limited due to poor growing conditions or overstocking, they may graze these plants.
Prevention
Prevention is any activity that keeps weeds from infesting a pasture. Most of the weeds are spread by seed. Thus, preventing the movement of weed seeds onto the ranch reduces potential weed pressure. Weed seeds can be transported in hay, harvested grass seed, sod, cattle, and mowing equipment, or dispersed by wind, water, and wildlife. Producers should avoid buying hay or grass seed that is contaminated with weed seeds. Do not purchase hay from someone who cannot provide a weed-free product. Using certified forage seed reduces weed seed contamination and is highly recommended.
Also, consider prevention of TSA while moving cattle to a new location. Cattle have been shown to excrete TSA seeds for at least 7 days after consumption. If cattle are grazing in a TSA-infested pasture, holding them in a clean area for 10 days before moving them to a new pasture is recommended. This will reduce the likelihood of transporting TSA seeds. Remember that an ounce of prevention is worth a pound of cure.
Control
Cultural Control
Cultural practices improve weed control by increasing the competitiveness of the forage. This involves optimizing forage production through monitoring of soil pH, fertility, and potentially irrigation management. Generally, a thick sward will prevent weed emergence, outcompete emerged weeds, and capture the majority of environmental resources (light, water, nutrients) necessary for growth. The aim of cultural practices is to modify your management program so that the sward is as competitive as possible.
Soil pH is an important factor for forage growth as well as weed establishment. UF/IFAS forage agronomists and soil scientists have determined the optimum soil pH for most forages grown in Florida. Acidic soils limit plant growth and can result in aluminum and manganese toxicity as well as magnesium, calcium, phosphorus, molybdenum, and potassium deficiency. Soil acidity may also result in poor root growth, which can reduce water and nutrient uptake. Weeds that grow under such conditions can be indicators of low soil pH. For example, flat-top goldenrod tends to be found in pastures with soil pH levels between 4 and 5, which are too low for optimum forage growth. Thus, the presence of flat-top goldenrod in your pasture may warrant a soil test and corrective action.
Mechanical Control
Mowing is one of the most often-used weed control methods in pastures. Mowing improves the appearance of a pasture, temporarily increases forage production, and, if properly timed, prevents weeds from producing seed. Mowing is generally more effective on broadleaf weeds than grass weeds and on annual weeds than perennial weeds. Carefully consider the cost of mowing and the anticipated effectiveness. As fuel prices increase, it may be more cost-effective to avoid mowing and use other forms of weed control because other weed control methods may be more effective on a given species.
Mechanical weed control does have drawbacks. Large weeds with extensive root systems will not be controlled by mowing alone. Additionally, mowing misses prostrate-growing weeds such as crabgrass, spurges, and matchweed. Mowing can also spread vegetative plant stems, allowing the plant (e.g., prickly pear) to root elsewhere. If mowing is performed after seed set, seeds can accumulate on the mowing equipment and worsen the weed problem by spreading to other pastures.
Biological Control
Biological control involves the use of biotic agents (e.g., plants, herbivores, insects, nematodes, and phytopathogens) to suppress weeds. Overall, biological control is still in its infancy, but great strides are being made, especially against invasive plants. Two good examples are the tobacco mild green mosaic tobamovirus (TMGMV) and the insect, Gratiana boliviana, both used for TSA control. The virus TMGMV can be sprayed to control existing TSA plants, while the beetle is used primarily for suppression.
Most biological control agents rarely provide complete weed control, but they usually suppress the weed population to a manageable level. Additionally, biological control agents are rarely fast-acting, so time is needed for the agent to suppress a given weed population. For example, the effect of Gratiana boliviana is often not seen until the year after the release of the beetle.
Chemical Control
Chemical weed control includes the use of herbicides. Herbicides kill weeds by inhibiting plant processes necessary for growth. Herbicides should be selected based on the forage species being grown, the weed species present, the cost, and the ease of application. Application method and environmental impact should also be considered.
Proper herbicide choice and application rate are extremely important. Lower-than-recommended application rates will not provide consistent weed control, while excessive application rates may cause injury to the forage or result in only killing the aboveground portion of perennial weeds. Additionally, herbicides must be applied at the right time to be cost-effective.
Preemergence (PRE) applications are made before weeds germinate and emerge. Understanding the life cycle of the weed is important when using a preemergence herbicide. Some weed seeds germinate in the summer, while others germinate in the winter months. Always refer to the herbicide label for additional information about controlling specific weeds.
Postemergence (POST) applications are made after the weeds emerge. The most effective and cost-efficient applications are made when the weeds have recently emerged and are small (3 to 5 inches tall). For perennial weeds (regrowing from root storage organs), it is advisable to allow them to bloom before spraying. This allows sufficient leaf surface for coverage and ensures that the perennial is transporting photosynthates back to the roots.
Postemergence herbicides may be broadcast over the entire pasture or may be applied as a spot treatment to sparse weed patches. Spot treatment is less costly compared to broadcast spraying. Other application methods include wipers and mowers that dispense herbicide while mowing the weed. Carefully read the herbicide label before purchasing to determine if that herbicide controls the weeds in your situation.
Precautions When Using Phenoxy or Benzoic Acid Herbicides
- For information about growth-regulating herbicides not covered below, see https://edis.ifas.ufl.edu/wg051.
- Application of other pesticides from sprayers previously used for 2,4-D, dicamba, or other phenoxy or benzoic acid herbicides to susceptible crops may result in injury.
- Legumes in pastures or rangelands will be injured or killed by these herbicides.
- Avoid drift to susceptible crops by applying at low pressures and when wind speeds are low and blowing away from susceptible crops. The use of a drift-control additive is advisable.
- Clean the sprayer thoroughly as described on the herbicide label. If no instructions are provided, you may follow the procedure below using household ammonia:
a. Flush system with water. Drain.
b. Flush the system with ammonia (1 qt ammonia per 25 gallons water); let it circulate for at least 15 minutes, then flush the system again. Drain again.
c. Remove screens, strainers, and tips, and then clean in fresh water.
d. Repeat step 5b.
e. Thoroughly rinse the tank, hoses, booms, and nozzles.
f. Be sure to clean all other associated application equipment.
Forage Tolerance
Not all cultivars of a particular forage species respond similarly to a given herbicide (Table 5). Argentine bahiagrass tolerates most pasture herbicides except Roundup, while Pensacola bahiagrass may be severely injured by metsulfuron-containing products, such as Cimarron and others. All herbicides may be used on stargrass and bermudagrass, with some level of injury from Velpar (hexazinone). Hemarthria, also known as limpograss, is the most sensitive to herbicide applications of all forage grasses grown in Florida.
Note that the response to an herbicide application can vary. For example, the chance for forage injury can increase or decrease as the rate of herbicide applied either increases or decreases. Additionally, environmental conditions such as high temperature and high relative humidity may increase the potential for herbicide injury. For example, we have observed little or no injury to limpograss from 8 pt/acre 2,4-D amine when applied under cooler conditions, while 4 pt/acre in warmer weather caused moderate to severe injury.
The response of forages in Table 5 is for established forage cultivars. However, 2,4-D + dicamba (2 pt/acre) can be applied to sprigged forage cultivars, except for limpograss, seven days after planting/sprigging. A forage can be considered established when at least three tillers are present on bahiagrass or at least 6 in of new stolon growth are present on sprigged forages.
Summary
Maintaining healthy, productive pastures will minimize the risk associated with weeds. Good pasture management practices such as adequate fertilization, insect control, and controlled grazing will result in healthy pastures. Unfortunately, weeds are present in pastures, and the associated loss in forage production can have serious economic implications. An integrated weed management strategy combining prevention, detection, and control is the most economical and environmentally friendly approach to pasture weed management.
Table 1.Weed control suggestions for pastures and rangeland. Contacts: Brent Sellers (sellersb@ufl.edu) and Pratap Devkota (pdevkota@ufl.edu). This table lists registered herbicides that should be integrated with other pest management methods. Contact your local UF/IFAS Extension office for additional information (https://ifas.ufl.edu/maps/).
Table 2.Estimated effectiveness of herbicides on common broadleaf weeds in pastures and hayfields (2,4-D through Impose/Panoramic).1
Table 3.Estimated effectiveness of herbicides on common broadleaf weeds in pastures and hayfields (Milestone through WeedMaster or others).1
Table 4.Estimated effectiveness of herbicides on common grass and sedges in pastures and hayfields.1
Table 5. Tolerance of established (for at least 6 months) forage cultivars to commonly used herbicides.
Table 6.Days between herbicide application to forage or pasture and feeding, grazing, or animal slaughter.
FAQs
What is the best way to control weeds in pasture? ›
Weeds should be hoed, pulled, or cut before they set seed and spread. Mowing is another option for weed control in pastures. Mowing on an interval that allows weeds to re-grow between mowing will eventually kill or reduce the number of some weeds.
Can you spray 2,4-D on pasture? ›Use of 2,4-D and dicamba for pasture weed control As mentioned previously, a combination of 2,4-D and dicamba is the standard herbicide treatment for controlling most broadleaf weeds in permanent grass pastures.
What time of year do you spray pasture for weeds? ›Management guidelines for some problem weeds of pastures
Apply an effective herbicide in fall or spring prior to bolting. Prevent seed production to prevent spread.
The results of the 2017 study suggests that mowing in June and August works as good as mowing every month to control weeds, and the June mowing will remove the seed heads.
What are 6 methods for managing weeds? ›- Prevention. The most important factor in overall weed control is to prevent weeds from developing seed and perpetuating the weed problem. ...
- Cultivation. ...
- Cover Crops. ...
- Mowing. ...
- Flaming. ...
- Hand-removal. ...
- Mulches. ...
- Soil Solarization.
- Step 1: Identify the Weeds You Have. ...
- Step 2: Select a Proper Herbicide. ...
- Step 3: Apply the Treatment. ...
- Step 4: Wait It Out. ...
- Step 5: Rake and Till. ...
- Step 6: Dethatch and Aerate. ...
- Step 7: Amend the Soil. ...
- Step 8: Lay Down Seed or Sod.
Sprays containing MCPB+MCPA, MCPB, bentazone or flumetsulam are commonly used to control a large spectrum of broadleaf weeds in new pasture. As long as the seedling pasture grasses and other species are at the right growth stage, they are safe too.
How long do horses need to stay off pasture after spraying 2,4-D? ›VPG advises to wait a minimum of 30 days after application of Hi-Yield 2, 4-D Selective Weed Killer before allowing animals to graze. 126 of 144 people found this answer helpful.
What herbicides are safe for grazing? ›There are a number of herbi- cides that can be safely used on grass pastures to control both annual and perennial broadleaf weeds. These herbicides include: Ally, 2,4-D (sold under many different trade names), Banvel, Crossbow, Stinger, Spike, and Weed Master.
Should you mow pasture after applying herbicide? ›For best control, herbicide should generally be applied in September or October, and current recommendations for systemic broadleaf herbicides are to withhold mowing at least 2 days before or after an application.
What do you spray on pastures in the fall? ›
Systemic herbicides may be applied after a frost if the plant is still actively growing. In summary, consider fall herbicide applications to reduce biennial and perennial pasture weeds. Identify the weeds to be targeted, understand their growth stage and timely apply the applicable herbicide at the correct rate.
Is it better to spray weeds in the fall or spring? ›Broadleaf herbicides applied in fall will be absorbed by the broadleaf weed's foliage and transported to the roots along with the carbohydrates, resulting in the destruction of the broadleaf weeds. Spring applications are generally less effective than fall applications.
Does mowing improve pasture? ›Mowing pastures is a strategy often used to eliminate seed heads in an effort to keep forages in a vegetative state and promote additional growth. As plants mature to a reproductive stage, they become less palatable to livestock and forage quality quickly decreases.
Is it better to mow before or after weed and feed? ›Can I mow my lawn before or after application of Yates Weed 'n' Feed? We recommend not to mow your lawn for 7 days before or after applying Yates Weed 'n' Feed.
Should you pull weeds before or after mowing? ›Rake weeds before mowing to pull seed stems upright. After mowing, destroy or dispose of seeds – don't add to your compost pile. Be careful not to rake if seeds are dropping, or you risk spreading seeds. As soon as perennial weeds sprout, it's time to take action.
Which one is the oldest method of controlling weeds? ›Hand weeding
It is probably the oldest method of controlling weeds and it is still a practical and efficient method of eliminating weeds in cropped and non-cropped lands. It is very effective against annuals, biennials and controls only upper portions of perennials.
Mulching over weeds works well to smother them, but you do need to make sure you mulch thickly enough. Using a layer of cardboard or newspaper (about 10 sheets per layer) will help prevent weeds emerging through. Lay this directly on top of the weeds, then put down a nice thick layer of mulch on top.
What kills weeds permanently naturally? ›The most effective homemade option is a mixture of white vinegar, salt, and liquid dish soap. Each of these ingredients has special properties that combine to kill weeds. Both the salt and the vinegar contain acetic acid, which serves to dry out and kill the plants.
How do farmers control weeds in fields? ›Chemical, cultural and mechanical weed control are the primary weed control methods used on farms today. Chemical weed control uses herbicides to kill or prevent the emergence of weeds.
How do you rejuvenate an old pasture? ›Many pastures are just in need of some "restoration." Examples of restoration include fertilization, liming, weed control and improving the movement of animals through the pasture to control grass height. Often, "restoration" can be applied and to bring pastures back to productivity.
Can cattle graze after spraying Roundup? ›
Depending on application, cattle can graze on treated pastures with no restriction on time (depending on dose) or up to a 7-d restriction. Yet, because glyphosate kills growing grass, most pastures are rarely, if ever, treated. Therefore, the majority of grass fed to cattle would have no residue since it is untreated.
How long after spraying 2,4-D can cattle graze? ›2,4-D amine* 2, 4-dichlorophenoxy broadleaf weeds Do not apply later than 30 days prior to acetic acid hay harvest. Do not graze meat animals (several formulations) on treated areas within 3 days of slaughter. Do not graze dairy animals within 7 days of application.
How long after spraying can you graze? ›Spray in the cool of evening or early morning to avoid scorching of grass. Avoid grazing sprayed areas for 10 days post spraying.
Can you leave horse poop in pasture? ›You can use manure onsite by spreading it as a fertilizer on an open area, pasture or field. You can also haul manure offsite for fertilizing or composting. Use caution when spreading manure on pastures grazed by horses. Don't spread manure on pastures if there are more than 1 horse per 2 acres.
Can horses stay in pasture overnight? ›If you keep your horse in a lush pasture at night, there isn't much you can do to keep them from eating and eating to their heart's content. However, if you stable them at night, then you're able to track exactly what and how much they're eating.
How often should you drag your pasture? ›Dragging paddocks two to three times a year helps break up manure piles and kill parasites. Often, horses pick an area to defecate in and not graze. Dividing the pasture into smaller paddocks can help solve this problem.
What chemicals can farmers use to control weeds? ›The most effective and commonly used presowing herbicides are simazine and cyanazine at rates of 1–2 l ha− 1, while metribuzin and imazethapyr at 200 ml ha− 1 are used after sowing and before emergence.
What are the dangers of Grazon herbicide? ›Causes serious eye irritation. May cause damage to organs (Kidney) through prolonged or repeated exposure. Very toxic to aquatic life with long lasting effects. Keep away from heat/sparks/open flames/hot surfaces.
Does Roundup have grazing restrictions? ›Resource Do not graze animals on green forage or use as feed prior to 28 days after application. Roundup PowerMAX Allow a minimum of 7 days for corn and 14 days for soybeans between application and feeding of treated vegetation.
Can you spray pasture for weeds in summer? ›Early to mid-June is a popular time to spray pasture weeds and woody plants. I'm not always sure, though, that it's the smart thing to do. Why do you spray weeds in pasture?
How low should I mow my pasture? ›
Mowing helps promote a nutritionally higher quality pasture. Shorter grass species such as Kentucky bluegrass and perennial ryegrass should be mowed to 2-3 inches, while a 3-4 inch mowing height is recommended for taller grass species such as orchardgrass and tall fescue.
How long do herbicides stay in hay? ›These herbicides eventually break down through exposure to sunlight, soil microbes, heat and moisture. Depending on the situation, the herbicides can be deactivated in as few as 30 days, but some field reports indicate that breakdown can take as long as three to four years.
What do farmers spray the field with? ›Pesticides help protect plants from pests and diseases. They are used by farmers to control pests such as weeds or insects that damage and destroy food crops and to tackle diseases such as potato blight.
When should you overseed pasture in fall? ›On the other hand, if you plan on planting seed pasture for the winter, the best time to begin seeding is in the fall. You can start as early as July for some grasses, but most recommend between August and September for the best results.
What do farmers spray on fields in fall? ›Conventional farmers spray glyphosate on genetically engineered corn, oats, soybeans and wheat before it is harvested. Consumers also use glyphosate on their lawns and gardeners.
How many times a year should you spray for weeds? ›Generally speaking, a grass and weed killer needs to be applied before the seeds are set and before they have had a chance to begin growing. You should make sure that you apply weed killers at least two times each year because no weed killer is permanent. All weeds will grow back in time.
Is it better to pull weeds when the ground is wet or dry? ›Weed when the soil is wet and soft. Pull weeds soon after watering your plants or a rain shower; when the soil is moist, the whole weed is more likely to come out by the roots. It's perfectly fine to put pulled weeds in your compost bin, where the naturally hot temperatures will destroy any seeds.
How long does 2,4-D need to be on before rain? ›2,4-D No delay indicated on label. A 6- to 8-hour rain-free period is suggested for the amine formulations, while the suggested rain-free period for the ester is one hour. Herbicide Delay Assure II Do not apply if rain is expected within one hour of application.
How do you get rid of weeds in pastures? ›Weeds should be hoed, pulled, or cut before they set seed and spread. Mowing is another option for weed control in pastures. Mowing on an interval that allows weeds to re-grow between mowing will eventually kill or reduce the number of some weeds.
When should I spray pasture for weeds? ›When is the Best Time to Spray Pasture Weeds? According to Dow AgroSciences forage specialists, since pastures typically contain a mix of weeds, a general recommendation is to spray when they are actively growing. That's usually early in the season.
Does Bush hogging help pasture? ›
“The simple act of brush-hogging is important for weed management, maintaining forage quality, and reducing grazing patterns,” Martel says. “Brush-hogging after livestock have grazed and moved on to the next field can help maintain quality and reduce patterns.
Why is my weed and feed not killing weeds? ›The problem is that the timing for effectively controlling weeds and effectively feeding your lawn simply do not add up. The high nitrogen, quick release fertilizers found in weed and feeds are not effective until grass is actively growing and out of dormancy. By that time your lawn will be full of weeds.
What is an alternative to weed and feed? ›Corn gluten meal is an organic alternative to weed 'n feed. Another effective method of controlling dandelions is pulling them manually.
Is rain good for freshly cut grass? ›7: Don't Cut Wet Grass
The best time to mow is when grass is dry. When moisture from rain or the morning dew weighs grass down, the blades bend, making a straight cut difficult. You also can slip on wet grass, and the clippings tend to clump and not spread evenly.
Tip. Flame weeding is considered an organic method of weed removal. However, if the weather is hot and the fire danger is moderate to extreme, Roundup may be the better option to avoid accidentally starting a fire or risking fines from the local fire district or other government agency.
What time of year should you pull weeds? ›Pulling Annual Weeds by Hand
The best time to hand-pull weeds is after a good rain. In fact, there's a weeding technique called “pre-sprouting” where you purposefully wait until right after a good spring rain to weed the garden because they tend to miraculously pop up at this point.
Roundup will spill into the soil as those applying it spray the solution on and around weeds.
What are the four methods of controlling weeds? ›Such methods include pulling, digging, disking, plowing and mowing. Success of various mechanical control methods is dependent on the life cycle of the target weed species.
What kills weeds and makes grass grow? ›The most effective homemade option is a mixture of white vinegar, salt, and liquid dish soap. Each of these ingredients has special properties that combine to kill weeds. Both the salt and the vinegar contain acetic acid, which serves to dry out and kill the plants.
What is the #1 method of controlling weeds in crops? ›Hand hoeing and pulling are the earliest (historically) and simplest types of weed control. Still a major weed control method for about 70% of the world's farmers (primarily in less industrialized countries). Kills by severing, dislodging, or burying plants and seeds. All tillage operations will help to control weeds.
How do farmers get rid of weeds? ›
Crop rotation is the most effective form of cultural weed control used to minimize weed infestations. Crop rotation is planting different crops in succession on the same field — this aids in breaking up many pest cycles including insects, diseases and weeds.
What kills weeds permanently but not grass? ›Tenacity herbicide is an industry favorite for killing weeds in your lawn without killing your grass. Optimized for cool-season turf, Tenacity can be used as a pre and post-emergent herbicide control for over 46 broadleaf weed and grass species.
What is the best grass to choke out weeds? ›Zoysia is ideal because it actually grows differently. It sends out runners or "stolons," expanding sideways more than it grows tall. This is why it is so dense and effective at choking out most summer weeds and replacing existing grass.
What kills only weeds and not grass? ›Selective herbicides are the only weed killers that won't kill your grass. While pre-emergent herbicides won't kill the grass that is already growing, they will stop further seeds from germinating.
How do modern farmers control weeds? ›Herbicides are considered the most effective and time-efficient method of weed control. Some herbicides are formulated so as not to cause harm to the surrounding plants of the weed. Chemical control is an effective way of controlling weeds.
What are the two effective methods to control weeding? ›Fallow management: Kill weeds in fallow fields (e.g., use tillage) to prevent flowering, seed-set and the build-up of weed seeds in the soil (Remember: “one year of seeds, seven years of weeds”). Crop-weed competition: Select a weed-competitive variety with early seedling vigor, and high tillering to suppress weeds.