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Cocklebur or Burdock—What’s the Difference?
Have Burs Will Travel
Autumn olive is an invasive woody shrub or small tree that grows to about 20 feet in height. The plant is commonly found invading open and early-successional woodlands, abandoned agricultural fields, and edges of streams and rivers.Read More
By CELESTINE DUNCAN
Garlic mustard (Alliaria petiolata) is a cool-season, invasive, herbaceous plant that is invading temperate forests throughout much of North America (Figure 1). The plant is native to Eurasia and northern Africa, and was introduced into the U.S. for food and as a medicinal plant. It is well established in the upper Midwest and eastern U.S., and is reported across the northern half of the U.S., Alaska, and parts of Canada.
Garlic mustard is shade tolerant and can move into stable forest understory where it rapidly out-competes native vegetation. Once established, the plant is capable of forming near-monotypic stands that suppress growth and recruitment of native plants and tree seedlings. Research has shown that garlic mustard can interrupt the associations that plants form with mycorrhizal fungi.
Garlic mustard is a biennial or short-lived perennial that can grow to about 3 feet in height. Seeds germinate early in spring, and new seedlings produce numerous kidney-shaped basal leaves that remain green throughout winter (Figure 2). In the second year, plants develop a vertical stem with alternative leaves that are more triangular or heart-shaped (Figure 3). All foliage produces a garlic-like odor when crushed. Stems often branch near the top and have individual flowers that alternate up the stem. Flowers have four white petals about ¼ inch long, four sepals, and six stamens. Fruits are long and linear, and individual plants can produce up to 8000 seed.
Garlic mustard is difficult to eradicate once plants have established and produced seed. Since the plant quickly invades disturbed sites, management efforts should strive to reduce soil and vegetation disturbance. Early detection and removal of new infestations before they produce seed will reduce the need for long-term management. If plants have produced seed, the site must be monitored and germinating seedlings removed for at least 10 years if eradication is the goal.
Garlic mustard spreads from established infestations along an invasion front. Small, satellite infestations often occur along trails, roads, or forest edges by seed transport. Management priority should be given to removal of these satellite infestations.
Field trials were conducted on garlic mustard to compare efficacy of Vastlan® and Garlon® 4 Ultra specialty herbicides to Accord® XRT II herbicide. Results of the study showed that both Garlon 4 Ultra and Accord XRT II provided excellent control of garlic mustard 38 days after application (Figure 4). Garlon 4 Ultra is a selective herbicide that will control garlic mustard and allow desirable grasses to thrive. Apply Garlon 4 Ultra at 16 to 32 fluid ounces of product per acre (oz/A), or as a spot application of 1.25 percent volume to volume (% v/v). Applications should be made to foliage in spring when plants are in the rosette growth stage. Use caution when applying herbicide solution near stems of desirable woody plants as injury may occur.
Accord XRT II applied at 1 to 1.5% v/v provides effective control of garlic mustard seedlings and rosettes. Accord XRT II is a non-selective herbicide, which can kill or damage most plants that are contacted by the spray solution. Garlic mustard must be actively growing to absorb the herbicide. Applications of Accord XRT II in late winter and early spring can often be timed for periods when few if any other plants beside garlic mustard are actively growing.
Physical and Mechanical Control
Individual garlic mustard plants can be controlled by digging. Cutting the entire taproot with a sharp shovel or spade 1 to 2 inches below the soil surface will control plants. Soil disturbance should be minimized to reduce garlic mustard reinvasion. Mowing or cutting of above-ground growth should be done as low as possible to reduce flowering and seed production. If garlic mustard is flowering, it is important to remove all cut stems since viable seed may be produced even if the stem is severed from the root. Because mechanical cutting does not remove the root crown, it may be necessary to cut multiple times in a growing season to prevent seeds from developing on secondary stems that sprout from the rootstock. Mowing may impact desirable non-target vegetation.
The effectiveness of fire as a control tool for garlic mustard differs based on site characteristics. Research shows that dormant-season fires do not control garlic mustard; however, fires conducted after garlic mustard emergences but prior to emergence of desirable plants may be effective. Repeated burns (fall, spring, spring; or spring, spring, spring), have been used to maintain garlic mustard in a reduced condition and stimulate herbaceous species richness and cover. Integrating herbicide treatments with fire may be more effective than fire alone.
Research is underway to develop biological control of garlic mustard. Currently, six species are identified as possible candidates for biological control agents. Future biological controls will be an essential component of integrated management of garlic mustard.
®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow.
State restrictions on the sale and use of Garlon 4 Ultra specialty herbicide and Accord XRT II apply. Consult the label before purchase or use for full details.
Vastlan specialty herbicide is not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state.
Always read and follow label directions.
Active ingredients for herbicide products mentioned in this article: Vastlan specialty herbicide (triclopyr-amine), Garlon 4 Ultra (triclopyr-ester), and Accord XRT II (glyphosate).
By CELESTINE DUNCAN
Purple loosestrife (Lythrum salicaria L.) is a perennial, rhizomatous forb that invades riparian areas and other waterways throughout most of the U.S. and southern Canada (Figure 1). The plant was first introduced into North America in the early 1800s as an ornamental and subsequently escaped cultivation. It is currently reported in all U.S. states, except Florida and Hawaii, as well as in nine Canadian provinces.
Purple loosestrife spreads primarily from seed, but new plants can also establish from root fragments and stem cuttings. Aerial shoots arise in spring from buds at the top of the root crown and can grow to more than 8 feet in height. Stems are square-shaped, five- or six-sided, and can be either smooth or covered with downy hairs. Bright rose to purple flowers are the most identifiable characteristic of the plant. Flowers are arranged on a spike, which can be a few inches to 3 feet long (Figure 2). The seed capsule is two-celled and contains very small seeds, with individual plants producing about 2.7 million seeds. Root crowns can spread to about 20 inches in diameter in a mature plant.
Successful management of purple loosestrife requires integrating various control methods. Pulling and digging can be effective on individual plants that are not well established. Selective herbicides alone and in combination with biological control agents can effectively contain and control estab-lished infestations.
Field studies conducted on purple loosestrife show that Vastlan® specialty herbicide at 1 to 1.5 percent solution (4 to 6 quarts of Vastlan per acre) will provide good control of loosestrife for up to one year following application (Table 1).
[ 1 ] Data averaged from two field trials for 64-80 DAA; and from one site 377 DAA. Total application volume ranged
from 30 to 50 gallons per acre.
[ 2 ] Percent solution is based on “spray to wet” total application volume of about 100 gallons per acre.
A non-ionic surfactant approved for use in aquatic environments should be added to the spray mixture at 0.25 percent volume to volume (1 quart in 100 gallons of water).
Purple loosestrife often establishes and flourishes on non-irrigation ditches and seasonally dry wetlands. On these sites, Milestone® specialty herbicide applied at 7 fl oz/A, or at the spot treatment rate of 14 fl oz/A, will provide good to excellent control for a year or more after application (Table 1). The addition of 1 pint per acre of 2,4-D with Milestone at 7 fl oz/A provides additional control.
Rodeo® at 1 to 1.5 percent solution (4 to 6 quarts Rodeo per acre) will control purple loosestrife (Table 1). However, it is important to note Rodeo is non-selective and will injure or kill desirable grasses (Figure 3). Vastlan and Milestone are selective herbicides that will control broadleaf plants but will not kill cattail or desirable grasses at the recommended application rate.
Herbicides should be applied at the bud to mid-flower growth stage. Plant foliage should be thoroughly wetted with the herbicide solution during application. Follow-up applications will be needed a year after treatment to control seedlings and any regrowth that may occur from mature crowns.
Purple loosestrife is often difficult to locate until the plant blooms. Clipping, bagging and removing flower heads from the infested site may be necessary to stop seed production at mid-flower growth stage and beyond.
Biological control agents alone and in combination with herbicides can be used on large, well-established purple loosestrife infestations.
Four species of beetles were introduced into the U.S. and Canada to control purple loosestrife. Galerucella pusilla and G. calmariensis are leaf-eating beetles that affect growth and seed production by feeding on leaves and new shoot growth of purple loosestrife plants. Hylobius transversovittatus is a root-boring weevil that deposits its eggs in the lower stem of purple loosestrife plants. The flower-feeding weevil, Nanophyes marmoratus, reduces seed production of purple loosestrife. The two Galerucella spp. have been the most successful of the four agents in establishing and reducing purple loosestrife density in the U.S.
Long-Term Management and Treatment
Loosestrife produces a vast quantity of seed that can germinate following herbicide application. Once the original infestation is controlled, new plants must be managed for several years. Long-term monitoring, vigilantly controlling newly emerging plants, and encouraging a desirable plant community will reduce reinvasion potential of purple loosestrife.
® ™ Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow. Milestone and Vastlan specialty herbicides are not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state.
Label precautions apply to forage treated with Milestone and to manure from animals that have consumed treated forage within the last three days. Consult the label for full details. Always read and follow label directions.
Active ingredients for herbicide products mentioned in this article: Milestone specialty herbicide (aminopyralid), Vastlan specialty herbicide (triclopyr-amine), Rodeo (glyphosate), and 2,4-D (2,4-Dichlorophenoxyacetic acid).
Saltcedar (Tamarix ramosissima, T. pentandra, T. chinensis, and T. parviflora) and Russian olive (Elaeagnus angustifolia L.) are rapid growing, non-native deciduous trees that were introduced into the United States for erosion control (saltcedar), windbreaks (Russian olive) or as ornamental plantings.Read More
Russian olive (Elaeagnus angustifolia) is a rapid-growing, deciduous, woody shrub or small tree that is invasive in riparian areas, lake shores and natural areas. The invasive plant can cause serious ecological changes to riparian habitats with impacts to wildlife and watershed values, agriculture, and recreation. There are several management options for Russian olive depending on tree size, density, and environmental constraints. The following information summarizes herbicide options for Russian olive management that can be used any time of the year including winter and early spring when trees are dormant.Read More
Spring and early summer can be excellent times to control actively growing invasive plants with herbicides. Applying herbicides to the target plant at the optimum growth stage is important to maximize control. The following guidelines provide information on the best application timing and rate to control key invasive plants.Read More
Several biennial thistles are problematic in North America including bull thistle (Cirsium vulgare), musk thistle (Carduus nutans), plumeless thistle (Carduus acanthoides), and Scotch thistle (Onopordum acanthium).Read More
Scentless chamomile, also known as daisy or scentless false may-weed (Matricaria perforata or Tripleurospermum perforatum), is an annual, biennial, or rarely perennial forb. The weed is widespread in Canada, Alaska, and much of the United States (Figure 1). It establishes well in moist, disturbed areas along streambanks, meadows, riparian areas, pastures, and hayfields.Read More