We have sensitive fern in our horse pasture. How concerned should I be about...
In our OSU Horse Nutrition Bulletin 762, the Sensitive Fern (Onoclea sensibilis) is not included as a poisonous plant, bracken Fern (Pteridium aquilinum) is. However In Penn State publication,Sensitive fern is listed as a poisonous plant.see below. I would eliminate it by mechanical means and remove from the field. Spraying for a broadleaf would be OK just read the labels for use and effectiveness.
Weed Management in Pasture Systems
Agronomy Facts 62Weeds can produce allelopathic substances that are toxic to crop plants. In addition, plants such as poison hemlock (Conium maculatum), white snakeroot (Eupatorium rugosum), and black locust (Robinia pseudoacacia) have toxic properties that can cause livestock injury or loss under certain circumstances. To plan an effective weed management program, a producer must be able to identify weeds and understand how weed biology and ecology affects where weeds are found and their value or detriment.
CompetitionWeed competition in pasture systems has not been extensively examined. In addition, the bulk of the competition research in higher rainfall areas like the Northeast has been conducted in Australia or New Zealand, not in the United States. In pasture, weed control decisions are based largely on visual thresholds and intuition. Reliable biological information or cost-benefit analysis is rarely available to support weed management decisions. Without question, weeds can compete directly with forage grasses or pasture to reduce their nutritional value and longevity. However, the impacts of weed species, density, and soil and climatic factors are not well established in pasture systems.In general, biennial and perennial weeds pose the biggest problems for pasture producers. Both biennials and perennials produce seed each year, potentially starting new infestations. Perennial weeds such as tall ironweed (Vernonia altissima), Canada thistle (Cirsium arvense), and multiflora rose (Rosa multiflora) reproduce from underground roots or rhizomes. Perennial rooting structures can survive for several years in the soil and are often unaffected by occasional mowing or livestock grazing. Pasture-invading weed species should be assessed for their competitive ability, or their potential to reduce desirable forage species; their invasiveness—their potential to multiply and increase; their yield, quality, and nutritive value relative to desirable forage species; and the cost and effectiveness of control measures—cultural, mechanical, and chemical.General rules about weed competition in forages include:
- Assess weed competitive ability, invasiveness, nutritive value, and potential to control.
- Weeds that emerge with the crop in the spring are generally more destructive.
- Control problem weeds for the first 60 days after seedling establishment.
- Weeds that emerge beyond 60 days after establishment will not influence that year’s forage yield.
- Later-emerging weeds may still influence forage quality.
- Winter-annual weed competition in early spring is most damaging to early-season forage yield.
- Broadleaf weeds that are biennial or perennial are generally more competitive than grassy weeds.
Weed QualityUnlike most grain or fiber crops from which weeds are separated at harvest, weeds are often harvested along with forage crops, potentially reducing quality. In the case of pasture, they remain in the field where they continue to interfere with desirable forage. Reductions in quality often take the form of lower protein content, feed digestibility, or even reduced intake by the animals.Although weeds do have some feed value, the value differs among species. The feed value of many pasture species has not been extensively studied. However, based on traditional forage quality measures—crude protein and digestibility—many weeds are nutritious and readily digested during the growing season (Table 1). Wild carrot (Daucus carota), a common pasture weed in some fields, has about 16 percent crude protein in the vegetative stage. Common yarrow (Achillea millefolium) has only about 10 percent crude protein during the flowering stage.
Poisonous PlantsMany plants contain poisonous substances that may be toxic to livestock if consumed. In addition, certain plants may be problematic because of mechanical irritation when eaten, photosensitization, and disagreeable tastes or odors in meat, milk, or milk products. If you suspect livestock poisoning, call a veterinarian immediately. If death occurs, the stomach contents should be examined for consumed herbage. Identify the suspected plants and remove livestock from the grazing area until all poisonous plants have been removed or destroyed. Table 2 lists some common weeds and their poisonous properties.
Prunus serotinaLeaves (wilted leaves are worse), stems, bark, fruit—anxiety, staggering, breathing difficulty, dilated pupils, bloat, deathCyanogenic glycosides—less than 0.25 lb leaves (fresh wt) can be toxic to 100- lb animalClover species
Vegetation—hairballs; sweet clover— nose bleed, anemia, abdominal swellingCoumarin in sweet clover—variesFern, brackenPteridium aquilinumEntire plant—dullness, fever, bleeding, loss of appetite, salivationGlycoside thiaminase—toxic to cattle fed a diet of 50% bracken fern for 30–80 daysGarlic, wildAllium vinealeAll plant parts—tainted milk and meatOnly toxic in large quantitiesHemlock, poisonConium maculatumAll plant parts—salivation, vomiting, diarrhea, weakness, paralysis, trembling, dilation of pupils, convulsions, comaConiine and others—0.5 to 4% (fresh wt) equivalent of cattle wt is toxicJimsonweedDatura stramoniumEntire plant (seeds are most toxic)— thirst, mood swings, convulsions, coma, deathSolanaceous alkaloids—0.06 to 0.09% (dry wt) equivalent of animal body wt is toxicLocust, blackRobinia pseudoacaciaLeaves (especially wilted), seeds, and inner bark—weakness, depression, anorexia, vomiting, diarrheaPhytotoxin robin, glycoside robitin—bark extract and powder in amount equivalent to 0.04 to 0.1% of animal wt toxic to horses. Cattle 10 times more tolerant.MilkweedsAsclepias speciesStems, leaves, and roots—muscle tremors, spasms, bloat, difficulty breathingGlycosides and galitoxin—variesMustardsBrassica, Thlaspi, and Lepidium speciesAll parts (especially seeds)—oral and gastrointestinal irritation, shaking, salivation, abdominal pain, vomiting, diarrheaThiocyanates, irritant oils, nitrates (large quantities generally necessary for toxicity)Nightshade speciesSolanum speciesVegetation, unripe fruit—loss of appetite, salivation, weakness, trembling, paralysisSolanine—toxic at 42 mg/kg (LD50)Pigweed speciesAmaranthus speciesFoliage—kidney disease, weakness, edema, rapid respirationNitrates, nitrate oxalates, unknown— sheep, hogs, young calves most susceptiblePokeweed species
Phytolacca americanaEntire plant, especially roots— gastrointestinal cramps, weakened pulse, respiration, salivationPhytolacctinm—10 or more berries can result in toxicity to humansSnakeroot, white
Eupatorium rugosumLeaves and stem—constipation, loss of appetite, salivation, rapid respiration. Toxin passes through milk (milksickness).Trophine alkaloid—varies from 1 to 20% of animal body wt. Toxin cumulative.St. JohnswortHypericum perforatumFlowers and leaves—photosensitivityHypercin—uncertain
- Some weeds have excellent nutritive quality.
- Weeds in the vegetative stage of development usually are more desirable than mature weeds.
- Regardless of weed quality, livestock may avoid grazing certain plants because of taste, smell, or toxicity.
- Some plants contain poisonous substances that may be toxic to livestock if consumed. Properly identify potential problem weeds and consult with a veterinarian if necessary.
Problem WeedsBased on their life cycles, weeds are grouped into three categories. Annuals complete their life cycle within one year and reproduce only by seed.Annuals may produce as few as 100 seeds or as many as 500,000 seeds per plant, depending on species and growing conditions. Annual weeds are classified as winter or summer annuals. Winter annuals germinate in the fall, overwinter as a rosette or small clumps of leaves, and complete their reproductive cycle in the spring or early summer. These weeds are more likely to be found in perennial forages and pastures where soils are not disturbed over the winter. Examples of winter annuals are given in Table 3.Summer annuals germinate in the spring and set seed in late summer or fall. They thrive when summer annual crops like corn or soybean are grown. They can also be a problem for new spring forage seedings during the establishment year or if established forages become thin or irregular. Summer annuals complete their life cycle in late summer or fall. Examples of summer annual weeds are provided in Table 3.
(Setaria)Knapweed, spotted (Centaurea maculosa)Pokeweed, common (Phytolacca
americana)Heal-all (Prunella vulgaris) Rose, multiflora (Rosa multiflora)Henbit (Lamium amplexicaule)Jimsonweed (Datura stramonium)Mullein, common (Verbascum thapsus)
Hemp dogbane (Apocynum cannabinum)
Horseweed/ marestail (Conyza canadensis)Lambsquarters, common (Chenopodium album)Parsnip, wild (Pastinaca sativa)
Horsenettle (Solanum carolinense)
Lettuce, prickly (Lactuca serriola)Nightshade, eastern black (Solanum ptycanthum)Thistle, bull (Cirsium vulgare)
Johnsongrass (Sorghum halepense)
Pennycress, field (Thlaspi arvense)Panicum, fall (Panicum dichotomiflorum)Thistle, musk/ plumeless (Carduus nutans/C. acanthoides)
Milkweed, common (Asclepias syriaca)
Pepperweed, field (Lepidium campestre)Pigweed species (Amaranthus)Cockle, white (Lychnis alba)
Nettle, stinging (Urtica dioica)
Radish, wild (Raphanus raphanistrum)Ragweed, common (Ambrosia artemisiifolia)
Nutsedge, yellow (Cyperus esculentus)
Shepherds-purse (Capsella bursa- pastoris)Smartweed, Pennsylvania (Polygonum pensylvanicum)
Quackgrass (Elytrigia repens)
Yellow rocket (Barbarea vulgaris)Velvetleaf (Abutilon theophrasti)
Red sorrel (Rumex acetosella)
Wirestem muhly (Muhlenbergia frondosa)
Yarrow, common (Achillea millefolium)
Yellow toadflax (Linaria vulgaris)
Smooth bedstraw (Galium mollugo)
Weed ManagementManaging weeds in pasture systems begins long before crop establishment. Certain types of weeds are potentially serious problems for forages, so it is important to eliminate them in advance. In particular, perennial broadleaves and grasses such as dandelion, curly dock, Canada thistle, and quackgrass (Elytrigia repens) are much easier to manage before planting a forage crop. In addition, biennial weeds including musk thistle (Carduus nutans) and burdock (Arctium minus) should be eliminated before establishing forage. If these weeds are not removed before the seeding is made, they can persist for many years. The cost of controlling weeds before or at the time of seeding should be considered an investment that will be returned for the life of the forage.Cultural ManagementCultural practices that aid in weed control include anything that makes the crop more competitive against weeds. In the establishment year, these measures include: preparing the seedbed properly, planting at the optimum planting date, fertilizing properly, planting at higher densities, using the correct seeding rate, choosing high quality crop seed that is free of weeds, and selecting adapted species and varieties for the region. In general, perennial grasses are more competitive against weeds than legumes are.Provide a seedbed at planting that is free of live weeds. A weed-free seedbed can be achieved using either tillage or a burndown herbicide. It is important that emerging forage species not have to compete for limited resources as they try to gain a foothold in the early weeks of establishment. In addition, emerged vegetation can harbor certain insects or pathogens that could attack young, susceptible forage seedlings.Date of planting can influence the kinds and numbers of weeds that emerge. Most grass and legume forage species are relatively slow to establish. Think about spring versus fall establishment based on weed history and what you might anticipate as problems. For example, if the field has been planted to corn or some other summer annual crop, then summer annual weeds will likely be the biggest weed threat during establishment. Late summer may be a better time for establishment in this situation. In spring seedings, plant early before summer annuals emerge to give the new forage seedlings every advantage. With late summer seedings, plant before September, the month during which winter annual weeds generally begin to emerge. The weed species present in a field, along with its potential severity, may help determine the best time for planting.In established pasture systems, prevention is the most important tool for managing weeds. Research shows that pasture weeds can be controlled by increasing forage competition. In fact, crop growth rate stands as the single best measure of plant response to weed competition in forages. Maintaining a dense, competitive forage is a key to preventing weed invasion and interference.Weeds are opportunistic. Germination and establishment are favored by open areas and by disturbance. Overseed with desirable forage species when necessary to keep open areas at a minimum. Rotationally graze to keep traffic effects minimal, and do not overgraze to ensure that forages remain competitive with weeds. Test soils for nutrients and annually fertilize to keep forage stands healthy and competitive. Control harmful insects or pathogens when necessary—they weaken forage stands and give weeds the opportunity to establish. Develop monitoring programs to locate infestations and place priority on controlling small infestations so that they do not expand.Preventing weed infestations also means preventing dispersal of seeds or vegetative structures into uninfested areas. Vehicles, humans, wind, water, birds, and livestock can spread weed seeds. Animals may disperse seeds by picking them up in their coats or fur, or between the pads of their feet. Cattle have been shown to readily pick up burs of several weeds when grazing forested range. Clean infested animals regularly, particularly new animals that may be carrying new weed problems. Ruminants also ingest weed seeds in the field—between 5 and 15 percent pass safely through sheep, goats, cattle, and deer. Be cautious of feed or hay infested with noxious weed seed. In the western United States, certified weed-seed-free forage is required on public lands by federal land agencies.Key points about cultural weed management:
- Consider seedbed preparation, planting date, fertilization, planting population, and high-quality crop seed, and select adapted species and varieties.
- In established pasture systems, prevention is the most important tool for managing weeds.
- Overseed with desirable forage species when necessary to keep open areas to a minimum.
- Rotationally graze to keep traffic effects minimal and do not overgraze.
- Test soils for nutrients and annually fertilize to keep forage stands healthy and competitive.
- Prevent dispersal of seeds or vegetative structures into uninfested areas.
- Repeated mowing reduces competitive ability, depletes root carbohydrates, and prevents seed production.
- Mow at a height above the grass seedlings when weeds are 8 to 10 inches tall to reduce shading.
- If you see a new weed, dig it, pull it, or remove the seedhead before seeds can disperse.
- Thin or irregular stands do not thicken once weeds are removed. Be sure there are sufficient desirable species to fill in the gaps, or overseed if necessary.
- Weeds tolerant of the herbicide may invade the space left by susceptible species, ultimately creating a more severe weed problem.
- If weeds make up 50 percent or greater of the stand, it is time to renovate or rotate to a different crop.
- If weeds become a problem in established forages, several herbicide options are available. Many products have harvesting, feeding, or grazing restrictions following their use.
RemarksaInformation taken from Blossey et al. 1994a; Blossey et al. 1994b; Groppe 1992; Kok 1992; McClay 1992; Powell et al. 1988; Smith et al. 1984; Sobhian et al. 1992; Story et al. 1989; Underwood et al. 1996; White and Marquardt 1989.Knapweed, spotted
(Centaurea maculosa)Root gall beetle (Sphenoptera jugoslavica)Larvae feed on root, weakening plants.Seedhead weevil (Bangasternums fausti)Larvae feed on seeds in seedhead.Seedhead fly (Chaetorellia acrolophi)Larvae feed on seedhead.Seedhead gall fly (Urophora affinis and U. quadrifasciata)Larvae feed on seedhead.Several others
Loosestrife, purple (Lythrum salicaria)European beetles (Gallerucella calmariensis and G. pusilla)Larvae feed on young buds, leaf, and leaf tissue.Weevil (Hylobius transversovittatus)Adults feed on leaves and larvae damage roots.Rose, multifloraRose rosette disease (Rosa multiflora)Mite-vectored virus (Some ornamental roses are also susceptible to this disease.)Rose seed chalcid (Megastigus aculeatus)Wasp adults lay eggs in seeds, rendering them sterile.Rose stem girdler (Agrilus aurichalceus)Larvae girdle and kill canes.Thistle: bull, Canada, musk, and plumelessSeedhead weevil (Rhinocyllus conicus)Feeds on the developing seedhead. Relatively effective where established. Less effective on plumeless and Canada.Rosette weevil (Trishosirocalus horridus)Larvae feed on young thistles.Toadflax, yellow (Linaria vulgaris)Weevil (Gymnetron antirrhini)Adults feed on buds, flowers, and seed capsules.Beetle (Brachypterolus pulicarius)Adults feed on young shoots and flower buds. Larvae feed inside the seedhead.
- Biological control tools for weeds include insects, mites, nematodes, pathogens, and grazing animals.
- Biological control can be cost effective, environmentally safe, self-perpetuating, and well suited to an integrated weed management program.
- Biological control is a long-term undertaking; it is not immediate or always adequate, only certain weeds are potential candidates, and the rate of failure can be high.
- Grazing does not in most cases eradicate a mature infestation of weeds.
- Combining mowing or a herbicide application with grazing can provide a wider window for control.
- Biological weed control may have a major impact on managing problem weeds in pasture systems in the future.
IntegrationAn integrated program that combines cultural, mechanical, chemical, and perhaps biological control tools can provide effective economic weed management in pasture systems. Consider how different tactics can be combined and remember how weed life cycle and other growth characteristics affect management options. Remember that prevention is the most important consideration for managing weeds in established pasture systems. Some general guidelines for managing annuals, biennials, and perennials are provided in Table 5.
- Blossey, B., D. Schroeder, S. D. Hight, and R. A. Malecki. 1994a. Host specificity and environmental impact of two leaf beetles (Galerucella calmariensis and G. pusilla) for biological control of purple loosestrife (Lythrum salicaria). Weed Sci., 42: 134-40.
- Blossey, B., D. Schroeder, S. D. Hight, and R. A. Malecki. 1994b. Host specificity and environmental impact of the weevil Hylobius transversovittatus, a biological control agent of purple loosestrife (Lythrum salicaria), Weed Sci., 42: 128-33.
- Bosworth, S. C., C. S. Hoveland , and G. A. Buchanan. 1985. Forage quality of selected cool season weed species. Weed Sci. 34:150-54.
- Bosworth, S. C., C. S. Hoveland, G. A. Buchanan, and W. A. Anthony. 1980. Forage quality of selected warm season weed species. Agron. J. 72:1050-54.
- Fishel, F. 2000. Plants poisonous to livestock. Agric. MU Guide, Missouri Extension, University of Missouri, Columbia.
- Groppe, K. 1992. Gymnetron antirrhini Paykull (Coleoptera: Curculionidae), a candidate for biological control of Dalmatian toadflax in North America. Intl. Inst. of Biol. Control European Station Final Report. 22 pp.
- Hardin, J. W. 1973. Stock-poisoning plants of North Carolina. Agric. Exp. Sta., North Carolina State Univ., Bulletin No. 414. Raleigh, NC.
- Hill, R. J., and D. Folland. 1986. Poisonous plants of Pennsylvania. Pa. Dept. Agric., Harrisburg, PA.
- Kok, L. T. 1992. Biological control of musk and plumeless thistles. Virginia Coop. Ext. Pub. 444-019:1-8.
- McClay, A. S. 1992. Effects of Brachypterolus pulicarius (L.) (Coleoptera: Nitidulidae) on flowering and seed production of common toadflax. Can. Entomol. 124: 631- 36.
- Powell, R. D., and J. H. Myers. 1988. The effect of Sphenoptera jugoslavica Obenb. (Col., Burprestidae) on its host plant Centaurea diffusa Lam. (Compositae). J. Appl. Ent. 106: 25-45.
- Smith, L. M., F. W. Ravlin, L. T. Kok, and W. T. Mays. 1984. Seasonal model of the interaction between Rhinocyllus conicus (Coleoptera: Curculionidae) and its weed host, Carduus thoermeri (Campanulatae: Asteraceae). Environ. Entomol. 13:1417-26.
- Sobhian, R., G. Campobasso, and P. H. Dunn. 1992. A contribution to the biology of Bangasternus fausti (Col., Curculionidae), a potential biological control agent of diffuse knapweed, Centaurea diffusa, and its effect on the host plant. Entomophaga 37: 171-79.
- Story, J. M., K. W. Boggs, and R. M. Nowierski. 1989. The effect of two introduced seedhead flies on spotted knapweed. Montana Agriculture Research, Montana, Montana State University, Bozeman, MT 59717-0278. Winter: 14-17.
- Underwood, J. F., M. M. Loux, J. W. Amrine, and W. B. Bryan. 1996. Multiflora rose control. Ohio State Univ. Bulletin 857. Columbus, OH.
- White, I. M., and K. Marquardt. 1989. A revision of the genus Chaetorellia hendel (Diptera: Tephritidae) including a new species associated with spotted knapweed, Centaurea maculosa Lam. (Asteraceae). Bull. Entomol. Res. 79: 453-87.