Exotic Pest Plants and Their Control

James H. Miller - USDA Forest Service, Southern Research Station, Auburn, Alabama.

Revised February 25, 2002.

The first line of defense against an exotic pest plant takeover is a constant surveillance of right-of-ways, stream banks, and internal roads and trails for any new arrivals. With the first appearance of an exotic invader, effective control measures should be started. Early detection and treatment will minimize efforts and costs that come with treating well-established plants or full-blown infestations. More effort is required for successful eradication of established infestations, but it still can be accomplished with proper treatments described here. In severe cases, a large-scale conversion of existing infestations is the only solution, involving eradication procedures using integrated management treatments and reestablishment of native plants. Fortunately in Southeastern forests, native plants in the soil seedbank or plants from surrounding areas will naturally reestablish once exotic invaders are eliminated.

Effective Treatments

If an exotic plant infestation is spotted or already occurs, then proper and aggressive eradication measures should be undertaken or spread is inevitable. Continued treatment and retreatments will be necessary to be successful. Most exotic invasive plants are perennials, having extensive tough roots and runners. This means that effective herbicide applications offer the best means of containment or eradication, because herbicides can kill roots and do so without baring soil for reinvasion or erosion.

The best approach is to use selective applications of herbicides to target exotic plants while avoiding or minimizing application to desirable plants. Selective methods (see details in later section) are:

1. Directed foliar sprays: herbicide-water sprays aimed at plant foliage to cover all leaves to the point of run off and usually applied with a backpack sprayer (use low pressure, drift retardants, and spray shields to avoid drift).
2. Stem injection (including hack-and-squirt): herbicide concentrate or herbicide-water mixtures applied into incisions spaced around woody stems made by an ax, hatchet, machete, brush ax, or tree injector.
3. Girdle-treat: herbicide concentrate or herbicide-water mixtures applied to an encircling band of removed bark around woody stems made by a cutting tool and applied with a spray bottle, wick, or paint brush.
4. Cut-treat: herbicide concentrate or herbicide water mixture applied to freshly cut stumps (outer circumference) or stems (entire top surface) with a backpack sprayer, spray bottle, wick, or paint brush.
5. Basal sprays: herbicide-oil-penetrant mixture sprayed or daubed onto the lower portion of woody stems usually applied with a backpack sprayer or wick applicator.
6. Soil spots: application of Velpar L herbicide as metered amounts to the soil surface around target woody stems or in a grid pattern for treating many stems in an area; usually applied with a spotgun or with a backpack sprayer equipped with a straight-stream nozzle.

To treat extensive inaccessible infestations, it may be necessary to use broadcast treatments of herbicide sprays or pellets by helicopter- or tractor-mounted application systems.

To be successful with herbicide treatments:

1. The most effective herbicide for the species should be used.
2. Applied using correct methods prescribed on the label.
3. Applied during an optimum time period for maximum herbicide effectiveness.
4. Follow and adhere to all label prohibitions, precautions, and Best Management Practices during herbicide transport, storage, mixing, and application.

As far as timing, foliar applied herbicides are often most effective in late-summer to early fall and not later than a month before expected frost.

Mainly herbicides registered by the Environmental Protection Agency for forestry use and noncrop lands in the Southeast will be discussed here. Herbicides in other "land use areas" (such as right-of-ways, pastures and rangelands, etc.) may be just as effective, or even contain the same active ingredient of those mentioned. The herbicides that will be recommended by trade name (and common name) are:

Because exotic pest plants are usually difficult to control it is often necessary to use herbicides that have both soil and foliar activity to be most effective with the least number of applications. When applying herbicides with soil activity, it should be recognized that damage to desirable plants might occur when their roots are present within the treatment zone, or when herbicides may move downhill following heavy rainfall to untreated areas. Garlon herbicides are mainly foliar active but have some soil activity at high rates and when mixed with oils. Garlon 4 and Vanquish have potential to volatilize at high temperatures and their residues can move by air currents to impact surrounding plants. Thus, applications should be avoided on days when temperatures exceed 80^oF. If possible, forgo applications during periods of severe drought as herbicide effectiveness can be greatly reduced during these times. Also, applications should not be make when rainfall is anticipated within two days, unless soil activation is needed.

When possible, use selective herbicides that target specific species of alien plants and minimize damage to surrounding desirable plants even though they receive herbicide contact, such as Transline that controls mainly legumes (e.g., peas and beans) and composites (e.g., asters, sunflowers, goldenrods, etc.). Also, damage to desirable cohorts can be minimized by making applications when desirable plants are dormant (e.g., basal sprays in late winter). For example, evergreen or semi-evergreen exotic plants can be treated when surrounding non-evergreen native plants have entered dormancy. Unfortunately, desirable woody plants can be damaged through transfer of herbicides by root grafts and root exudates when applying stem injection, girdle-treat and cut stump treatments to adjoining exotic woody plants, or when soil-active herbicides wash off treated stems. Damage to surrounding native plants can be minimized with care and forethought during planning and enactment of application.

Read and thoroughly understand the herbicide label and its prohibitions before and during use. Many herbicides require the addition of a non-ionic surfactant to the spray tank to be effective. Other important points are to always use clean water when required in a herbicide mixture and mix spray solutions thoroughly before applying. Mixing should not be done in the sprayer but in a bucket with a stirring stick—stirring for a minute or more—before transferring to the sprayer. When changing from a water-based mix to an oil-based mix in a backpack sprayer, always remember to thoroughly evacuate the water from the pump and run a small amount of oil through the pumping system before filling with the oil-based mix, or a white sludge will clog the sprayer. And, always wear your personal protective equipment prescribed on the label and in supplementary materials.

Other Treatments for an Integrated Approach

Overgrazing is a way to reduce the vigor of palatable invasive plants like kudzu, but this rarely yields eradication and may spread seeds (now occurring with tropical soda apple). Mechanical treatments and prescribed burning can assist eradication measures, but are limited in effectiveness. Prescribed burning does not control root-crowns or rhizomes of perennial plants and usually only kills small aboveground shoots, providing only temporary aboveground control. In a similar way, chainsaw felling or brush mowing woody exotic plants and mowing vines and herbs, without killing roots, remove only aboveground plant parts. Mechanical root raking and disking can actually spread or aggravate a problem when dealing with plants having runners by chopping these into resprouting segments. However, the use of root raking, piling, brush mowing, or burning may be the only way to start controlling dense infestations of multiple woody exotics. Small infestations may also be handled by hand pulling, grubbing with a stout hoe, or by using the newly introduced shrub-pulling devices. Hand pulling or grubbing may be the quickest and easiest way to halt invaders when first spotted so as to stop them from gaining a foothold.

Although ineffective by themselves to achieve eradication, both mechanical and burning treatments can give added kill of herbicide-weakened plants and have a place in an integrated pest management program. The stumps and stems of exotic trees, shrubs, and bamboos that are felled can be treated with herbicides immediately after cutting to kill roots. Resprouts of trees, shrubs, and vines that are topkilled by burning can be more easily treated with foliar sprays, often the most cost-effective way to use herbicides. Herbicide applications following burning or disking should be delayed to permit adequate resprouting of target plants for maximum herbicide uptake and effectiveness. Prescribed burning can also kill or stimulate seed germination of troublesome plants permitting effective herbicide control of germinants. Burning can also prepare the site for effective herbicide applications by clearing debris and revealing application hazards, such as old wells and pits. Disking and rootraking, if applied correctly, can dislodge herbicide-damaged woody roots and large runners, leaving them to dry and rot. Steps should be taken to prevent erosion when using mechanical and burning treatments. For example, burning in late winter or during spring leaf-out, minimizes the period of bare soil.

An eradication program for infestations of troublesome plants usually takes several years and surveillance for many more years to check for seed germination or new invasions. Doing this in a planned manner, and being persistent is the only successful strategy. In this way, land access, productivity, and native plants can be safeguarded and wildlife can continue to have suitable habitats.

The following are herbicide prescription summaries for prevalent exotic pest plants. These prescriptions have been assembled from my published and unpublished trials, other’s published research results, and reports in State and weed council’s manuals, magazines, and websites (refer to list at the end). In general, very few species-specific experiments have been performed and reported that compare a full array of treatments aimed at an exotic species. But until further specific understanding is gained, we must proceed using our current knowledge and technology to combat this exotic plant invasion.

Exotic Tree Control

Exotic tree species hinder right-of-way and natural area management, reforestation and dramatically alter habitat. Some occur as scattered trees while others form dense stands. Most spread by prolific seed production and abundant rootsprouts. Nondesirable trees can be eliminated using herbicides by stem injection, girdle-treat, soil spots, and for seedling and saplings, basal sprays and foliar sprays. Following stem control, surveillance and treatment of exotic plant germinants originating from the soil seedbank is the key step in the overall elimination and management of exotic trees.

Tree-of-heaven or Ailanthus (Ailanthus altissima) Nature: Deciduous tree to 80 ft tall with long pinnately compound leaves, gray slightly fissured bark, and large terminal clusters of greenish flowers in early summer. Flowers and other parts of the plant have a strong odor. Shade intolerant, flood intolerant, and allelopathic. Origin: Introduced beginning in 1784 from Europe, although originally from Eastern China. Uses: Ornamental tree. Herbicide control: For large trees, make stem injections

Silktree or Mimosa (Albizia julibrissin) Nature: Small legume tree to 30-50 ft tall that reproduces by abundant seeds and rootsprouts. It has feathery deciduous leaves, smooth light brown bark, and showy pink blossoms that yield dangling flat pods during winter. Partially shade tolerant. Seedpods float and seed remain viable for many years. Origin: Introduced from Asia in 1745. Uses: A traditional ornamental. Herbicide Control: For larger trees, make stem

Princesstree or Royal Paulownia (Paulownia tomentosa) Nature: Deciduous tree to 60 ft tall with large heart-shaped leaves being fuzzy hairy on both sides, pecan-like nuts in clusters (containing many tiny winged seeds) appear after showy pale-violet flowers in early spring. Reproduces by abundant seeds and rootsprouts. Invades burned and harvested sites. Origin: Introduced from East Asia in the early 1800’s. Uses: Ornamental and grown in scattered plantations for

Chinaberrytree (Melia azedarach) Nature: Medium tree growing to about 50 ft tall that spreads by bird-dispersed seeds. It has lacy, many-divided leaves that are dark green and blue flowers that yield round yellow fruit that persist during winter (poisonous to humans and livestock). Reproduces by abundant seeds and rootsprouts. Semi-shade tolerant. Origin: Introduced from Asia. Uses: Traditional ornamental and found around old home-sites, with potential uses of its extracts for natural

Tallowtree or Popcorn Tree (Triadica sebifera and formerly Sapium sebiferum) Nature: Shade-tolerant, small tree growing to 50 ft tall that spreads by bird-dispersed seeds and sprouting surface roots. It has light-green heart-shaped leaves turning scarlet in fall, long drooping flowers in spring, and bundles of white waxy "popcorn-like" seeds in fall and winter. Reproduces by prolific rootsprouts and abundant seeds spread by birds and water. Shade tolerant , flood tolerant, and allelopathic. Origin: Introduced from China to the U.S. Gulf Coast first in South Carolina in the 1700’s and then in significant numbers in the early 1900’s. Uses: Ornamental (still being sold and planted). Waxy seeds traditionally used to make candles. Encouraged by

Russian Olive (Elaeagnus angustifolia) Nature: Shade-intolerant, small thorny tree growing to 35 ft tall that spreads by bird-dispersed seeds. Microscopic silvery scales cover leaves, twigs, and fruits. Leaves are long and narrow with entire margins. Bark is smooth and reddish brown. Olive-like fruit are yellow and appear in fall. A recent invasive arrival in the northern part of the Southeastern Region. Origin: Native to Europe and western Asia being brought to the U.S. in the early 1900’s.

Exotic Shrub Control

Exotic shrubs often occur with exotic tree species and present similar problems. Herbicide control options are similar to trees, while foliar sprays can be used more often and most effectively.

Silverthorn or Thorny Olive (Elaeagnus pungens) Nature: Evergreen, bushy shrub with long limber projecting shoots to 16 ft tall with alternate leaves, silver scaly in spring on both top and bottom, and becoming dark green above and silvery beneath by mid-summer. Thorns widely scattered on branches. Oblong fruit are red and brown scaly appearing in spring. Shade tolerant. Origin: Introduced from China and Japan. Uses: Widely planted as an ornamental shrub. Herbicide Control: Apply Arsenal AC or Vanquish as 1% solutions in water (4 ounces in a 3-gal. sprayer) with a surfactant to thoroughly wet all leaves in April to October (can damage trees with roots in area). For stems too tall for foliar sprays, apply a 20% solution of Garlon 4 (2 quarts in

Autumn Olive (Elaeagnus umbellata) Nature: Deciduous, bushy shrub to 20 ft tall with alternate leaves, dark green above and silvery beneath, with many red spherical berries in fall having silvery scales. Fruit spread widely by birds and animals resulting in scattered plants in forests. Origin: Introduced in 1917 from China and Japan. Uses: Widely planted for wildlife habitat, strip mine reclamation, and shelterbelts. Herbicide Control: Apply Arsenal AC or Vanquish as 1%

Winged Burning Bush (Euonymus alata) Nature: Shade-tolerant and deciduous, bushy shrub to 12 ft tall with opposite leaves along stems with four corky-wings. In fall, leaves turn bright red while orange fruit appear as stemmed pairs in leaf axils. Fruit spread by birds and animals. Shade tolerant. Origin: Introduced from northeast Asia in the 1860’s. Uses: Widely planted as an ornamental. Herbicide Control: Apply Arsenal AC or Vanquish as 1% solutions in water (4 ounces in a 3-gal. sprayer) with a

Chinese Privet (Ligustrum sinense) European Privet (L. vulgare) Nature: Shade-tolerant, tall shrubs or small trees growing to about 30 ft tall that spread by bird-dispersed seeds and rootsprouts. Difficult to distinguish apart, both species have leafy stems with opposite leaves less than 1 inch long, with Chinese privet being semi-evergreen and European privet being deciduous. Both have showy clusters of small white flowers in spring that yield clusters of small spherical, dark-purple berries during fall and winter. Both are rapidly spreading and form dense exclusive stands. Origin: Introduced in the early to mid 1900’s from China and Europe, respectively. Uses: Traditional Southern ornamental shrubs. Deer browse

Japanese Privet (Ligustrum japonicum) Nature: Shade-tolerant, tall shrub or small tree growing to about 40 ft tall, with evergreen leaves, that spread by bird-dispersed seeds and by underground runners. Leaves are opposite, 1-3 inches long, and leathery. Showy clusters of small white flowers in spring yield clusters of small round, dark-purple berries during fall and winter. Spreads by bird-dispersed seeds and rootsprouts. Origin: Introduced from Japan and Korea in 1945. Uses: Ornamental shrub. Herbicide Control: Apply Garlon 4 as a 3% solution (12 ounces in a 3-gal. sprayer) or Arsenal AC as a 1% solution (4 ounces in a 3-gal. sprayer) in water with a surfactant to thoroughly wet all leaves in August through

Bush honeysuckles Amur honeysuckle (Lonicera maackii) Morrow honeysuckle (L. morrowii) Tatarian honeysuckle or Twinsisters (L. tatarica) Sweet-breath-of-spring (L. fragrantissima) Nature: Bush honeysuckles are multi-stemmed and arching-branched, generally deciduous shrubs 6 to 16 ft tall. Leaves are distinctly opposite, usually oval to oblong in shape, and range in length from 1 to 3 inches. Flowering usually occurs from May to June as fragrant, tubular flowers in pairs, being creamy-white in most species turning yellow or pink to crimson in varieties of Tatarian honeysuckle. Abundant paired berries are red to orange during winter. Seeds are long-lived in the soil. Origin: All from Asia and introduced in the 1700’s and 1800’s. Uses: Mistakenly used as ornamentals and wildlife plants. Herbicide Control: Apply a glyphosate herbicide as a 1% solution in water (4 ounces in a 3-gal. sprayer) with a surfactant to thoroughly wet all leaves in August to October. Or, apply a 20% solution of Garlon 4 (2 quarts in a 3-gal. sprayer) in commercially available basal oil, diesel fuel, or kerosene with a penetrant (check with herbicide distributor) to young bark completely around the trunk up to 16 inches above the ground. Cut large stems

Sacred Bamboo or Nandina (Nandina domestica) Nature: Bushy evergreen shrub with stems resembling a fleshy bamboo, with glossy, bipinnately compound leaves that are green to reddish tinged. Early summer terminal clusters of tiny white flowers yield dangling clusters of red berries in fall and winter. Spreads by animal dispersed seeds. Origin: Introduced from eastern Asia and India in the 1950’s. Uses: Widely planted as an ornamental. Herbicide Control: Apply a glyphosate herbicide as a 1% solution in water (4 ounces in a 3-gal. sprayer) with a surfactant to thoroughly wet all leaves in August to October. Apply a 20% solution of Garlon 4 (2 quarts in a

Exotic Roses Multiflora Rose (Rosa multiflora); Macartney Rose (R. bracteata); Cherokee Rose (R. laevigata); Swamp Rose (R. palustris); and other exotic roses Nature: Erect, arching, and trailing roses often forming infestations having pinnately compound leaves with 3-7 leaflets. Rose flowers of white to pink to red in early summer yield red rose hips in fall to winter. Origin: Introduced from Asia. Uses: Traditionally planted as ornamentals, livestock containment, and wildlife habitat. Herbicide Control: Apply Escort at 1 ounce per acre in water (0.2 dry ounces in 3-gal. sprayer) with a surfactant to wet foliage in April to June (at or near the time of flowering). Or, apply Arsenal AC as a 1% solution in water (4 ounces in a 3-gal. sprayer) and a surfactant to thoroughly wet all leaves in August to October. A less effective treatment with no soil activity to damage surrounding plants requires repeated applications of a glyphosate herbicide as a 2% solution in water (8 ounces in a 3-gal. sprayer) with a surfactant to thoroughly wet all leaves in May to October. With all herbicides, spray foliage of climbing stems as high as possible. Cut-treat with a 10%-20% solution of a glyphosate herbicide (1-2 quarts in 3-gal. sprayer) in water

Exotic Vine Control

Exotic vines are some of the most troublesome invaders because they often form the densest infestations, making herbicide applications difficult. Many of these vines overtop even mature forests and often form mixed-species infestations with exotic trees and shrubs. Specific herbicides can be effective on certain vines while not being effective on the underlying exotic trees and shrubs. Selection of the best herbicide or herbicide mixtures for mixed-species infestations requires more forethought. Vine control is always difficult because foliar active herbicides must move through lengthy vines to kill large unseen woody roots and tubers. Thus, herbicides that have both soil and foliar activity are often the most effective. A plus to this picture is that only the lower foliage within sprayer reach needs to be treated with a herbicide having both foliar and soil activity for successful control.

Oriental or Asian bittersweet (Celastrus orbiculata) Nature: This attractive but very invasive vine has elliptic to rounded deciduous leaves, 2-3 inches broad and long, alternating along a woody vine with drooping branches. Showy red-orange berries in clusters appear in fall and remain during winter at most leaf axils. American bittersweet (Celastrus scandens) has flowers and fruit only in terminal clusters. Birds spread seeds. Origin: Introduced from Asia in 1860’s. Uses: Ornamental with berried vines used as home

Exotic Climbing Yams Air yam (Dioscorea bulbifera) Chinese Yam or Cinnamon Vine (D. oppositifolia and formerly D. batatas) Nature: Twining and sprawling vines that cover vegetation, having smooth heart-shaped leaves and dangling small yam-like tubers at leaf axils in mid- to late-summer that drop and form new plants. Even though these vines are deciduous, their rapid growth in a year can cover small trees. Native Dioscorea species do not produce "air yams" nor form infestations that cover trees. Origin: Air yam is from Africa and Chinese yam is from Asia, with both being introduced as possible food sources in the 1800’s.

Wintercreeper or Climbing Euonymus (Euonymus fortunei) Nature: Evergreen plant that is trailing, climbing, or shrubby with opposite thick, dark-green or green-white variegated leaves. Spreads to form a dense ground cover and climbs by aerial roots along the stem. Seeds spread by birds. Origin: Introduced from Asia. Uses: Ornamental groundcover. Herbicide Control: Apply foliar sprays of Tordon 101 as a 3% solution (12 ounces in 3-gal. sprayer) or Tordon K at 2% solution (8 ounces in 3-gal. sprayer) in water with a surfactant to wet foliage until run-off in July to October for successive years (Tordon herbicides are Restricted Use Pesticides). Spray foliage of climbing vines as high as

Japanese Honeysuckle (Lonicera japonica) Nature: Shade-tolerant, climbing and trailing woody vine with semi-evergreen leaves that are opposite on the stem. It spreads by vines rooting at nodes and bird-dispersed seeds. Still planted in wildlife food plots. Origin: Introduced from Japan in the early 1800’s. Uses: Traditional ornamental, valued as deer browse, and has some value for erosion control. Herbicide Control: Broadcast apply Escort at 2 ounces per acre in water (0.6 dry ounces in 3-gal. sprayer) or spot spray 2-4 ounces per acre in water (0.6-1.2 dry ounces in 3-gal. sprayer) with a surfactant to foliage from July to September or from May to June when pine tolerance is needed. Apply a glyphosate herbicide as a 2% solution in

Kudzu (Pueraria montana, formerly Pueraria lobata) Nature: Semi-woody legume vine that spreads by vine growth, rhizomes, and seeds. Origin: Introduced from Japan and China in early 1900’s. Uses: Erosion control, livestock feed, and folk art. Herbicide Control: Apply foliar sprays of Tordon 101 as a 3% solution in water (12 ounces in 3-gal. sprayer) or Tordon K as a 2% solution in water (8 ounces in 3-gal. sprayer) with a surfactant to wet foliage until run-off in July to October for successive years (Tordon herbicides are

Exotic Vincas or Periwinkles Common Periwinkle (Vinca minor) Bigleaf Periwinkle (V. major) Nature: Trailing vines that form dense ground cover with opposite leaves, lanceolate to heart-shaped. Five-petaled pinwheel-shaped flowers appear in spring to early summer, with seed viability still in question. Shade tolerant. Origin: Introduced from Europe. Uses: Ornamental groundcover. Herbicide Control: Apply foliar sprays of Tordon 101 as a 3% solution (12 ounces in 3-gal. sprayer), Tordon K as a 2% solution (8 ounces in 3-gal. sprayer), or Garlon 4 as a 4% solution (15 ounces in 3-gal. sprayer) in water with a surfactant to wet foliage until run-off in July to October for

Chinese Wisteria (Wisteria sinensis) Japanese Wisteria (W. floribunda) Nature: Both are woody, leguminous vines (or shrubs) with long pinnately compound leaves and showy spring flowers. They spread by rooting vine growth and less so by seeds. Both form dense infestations while the native or naturalized American wisteria (Wisteria frutescens) does not form extensive infestations like the exotics. Origin: Introduced from Asia in the early 1800’s. Uses: Traditional Southern porch vines. Herbicide Control: Apply Tordon 101 as a 3 % solution (12 ounces in 3-gal. sprayer), Tordon K as a 2% solution (8 ounces in 3-gal. sprayer), or Garlon 4 as a 4% solution (15 ounces in 3-gal. sprayer) in water with a surfactant to

Exotic Grass Control

Exotic grasses continue to spread and increasingly reside along highway right-of-ways and thus gain access to adjoining lands. Most exotic grasses are highly flammable, increasing fire intensities while promoting their spread after wildfire or prescribed burns, with wildland firefighters subjected to increased risks. Exotic grasses have become one of the most insidious problems in the field of wildlife management, because they can totally dominate pasture and prairie lands once established, having little wildlife value and leaving no room for native plants. Repeated applications of herbicides are required for control.

Giant Reed (Arundo donax) Nature: Large leafy reed to 20 ft tall in clumps from dense branching rhizomes. Erect terminal flower stalks and seed heads appear in late summer, but no seed are produced. Spread is by rhizomes and movement of stem parts in soil or by road grading. Origin: Native to western Asia, northern Africa, and southern Europe and introduced in the early 1800’s. Uses: Ornamental. Herbicide Control: Apply a glyphosate herbicide as a 2% solution (8 ounces in a 3-gal. sprayer) or Arsenal AC as a 1% solution (4 ounces in a 3-gal. sprayer), or combination of the two herbicides in water with a surfactant to thoroughly wet all foliage in September or October with

Tall Fescue (Lolium arundinaceum and formerly Festuca arundinacea and F. elatior) Nature: Cool-season grass that is dark green year-round except in summer, with whitish-eared areas where blades connect to the stem and stems having swollen nodes. Certain varieties contain toxins poisonous to livestock and wildlife. Origin: Introduced from the Europe, and now widely distributed most everywhere in the world. Uses: Planted for improved pasture for livestock production, wildlife openings, and soil stabilization. Herbicide Control: For non-crop lands, apply a mixture of Plateau at 10-12 dry ounces + a glyphosate herbicide at 1 qt in 20 gal. water per acre in late summer or spring

Cogongrass (Imperata cylindrica) Nature: Dense, erect perennial grass with wide yellowish-green leaves having off-center midveins and finely saw-toothed margins. Spreads by wind-blown seeds in early summer and rhizome movement in fill-dirt along highways, yielding circular infestations. Highly flammable and a severe fire hazard. Origin: Native to Southeast Asia and introduced into FL and lower LA, AL, and GA in the early 1900’s. Uses: Improved forage initially projected but without success, and initially for soil stabilization. Herbicide Control: Apply a glyphosate herbicide as a 2% solution (8 ounces in a 3-gal. sprayer) or Arsenal AC as a 1% solution (4 ounces in a 3-gal. sprayer), or combination

Nepalese Browntop (Microstegium vimineum) Nature: Dense, mat-forming annual grass with stems growing to 1-3 ft long, often laying over, having alternate, lanceolate leaves to 4 inches long. Shade tolerant and occupies various habitats including creek banks, floodplains, forest roadsides and trails, damp fields, and swamps. Consolidates occupation and spreads by prolific seed production in late summer. Origin: Native to temperate and tropical Asia and introduced near Knoxville, TN around 1919.

Chinese Silvergrass (Miscanthus sinensis) Nature: Tall, densely tufted, perennial grass, upright to arching, 5-10 ft tall, long-slender leaves with whitish upper midveins. Silvery to pinkish loose plumes appear in fall, with spotty seed viability. Highly flammable and a fire hazard. Origin: Native to eastern Asia. Uses: Still widely sold and planted as an ornamental. Herbicide Control: Apply Arsenal AC as a 1% solution (4 ounces in a 3-gal. sprayer) or a glyphosate herbicide as a 2% solution (8 ounces in a 3-gal. sprayer), or a combination of the two herbicides in water with a surfactant to thoroughly wet all foliage in September to October, with multiple applications to regrowth.

Exotic Bamboos Golden Bamboo (Phyllostachys aurea) Other Exotic Invasive Bamboos (Phyllostachys spp. and Bambusa spp.) Nature: All bamboos that form extensive infestations besides the native switchcane (Arundinaria gigantea). All have jointed cane stems with bushy tops of long-pointed grass-like leaves on branching stems. Origin: All native to Asia. Uses: Ornamentals and fishing poles. Herbicide Control: Apply a glyphosate herbicide as a 4% solution (1 pint in a 3-gal. sprayer) or Arsenal AC (or Chopper) as a 3% solution (12 ounces in a 3-gal. sprayer), or combination of the two herbicides in water with a

Exotic Fern Control

Japanese climbing fern is presently the only exotic invasive fern in the temperate parts of the Southeastern Region.

Japanese Climbing Fern (Lygodium japonicum) Nature: Delicate viney fern with lacy finely divided leaves and green to orange to black wiry vines that climb and twine to cover and smother shrubs and trees. One of three species of climbing fern in the Southeast with the others being American climbing fern (Lygodium palmatum) and the exotic, old world climbing fern (Lygodium microphyllum) in Florida, which have once-divided leaves. All are perennial plants, from creeping rhizomes. Origin: Native to Asia and tropical Australia and

Exotic Forb Control

Forbs are broadleaf herbaceous plants. Control treatments are usually by foliar sprays of herbicides.

Garlic Mustard (Alliaria petiolata) Nature: A biennial herb, in small to extensive colonies under forest canopies, with basal rosettes of leaves in the first year (remaining green during winter) becoming 2-4 ft tall in the second year. Leaves broadly arrow-point shaped with wavy margins and flowers in terminal clusters having four white petals. All plant parts have an odor of garlic. Prolific seed producer and seeds lay dormant for 2-6 years before germination, with germination only in spring. Seeds spread by humans, animals and transported in fill-dirt.

Shrubby Lespedeza or Bicolor or Bushclover (Lespedeza bicolor) Chinese Lespedeza or Sericea Lespedeza (Lespedeza cuneata) Nature: Although still planted for quail food plots, these plants often invade surrounding forests, replacing native plants. Shrubby lespedeza is a shade-tolerant, 3-leaflet, shrubby legume up to 10 ft tall with small purple-pink pea-type flowers. Chinese lespedeza is not really a shrub, but a semi-woody plant to 3 ft tall with many small 3-leaflet leaves feathered along erect, whitish stems having tiny cream-colored flowers in leaf axils during summer. Both will form dense stands that prevent forest regeneration and land access. Origin: Both from Japan. Uses: Wildlife food for birds and soil stabilization. Herbicide Control: Apply Garlon 4 as a 2% solution in water (8 ounces in a 3-gal. sprayer) with a surfactant or Escort at 2 ounces per acre in water (0.6 dry ounces in 3-gal. sprayer) to thoroughly wet all leaves in July to September. Apply Transline as a 0.2% solution (1 ounce

Tropical Soda Apple (Solanum viarum) Nature: Thorny, upright plant with oak-shaped leaves and prolific golf-ball fruit that are mottled green white turning to yellow in late summer to fall. Spreading rapidly in the southern parts of the region with transportation by cattle that have recently ingested fruits and by wildlife feeding of fruits. Viable seed in both green and yellow fruit, but non-viable in white fruit. Consolidates infestations by rootsprouts. Origin: Native to Argentina and Brazil and introduced into

The Rehabilitation Phase

The rehabilitation phase is the most important final part of an eradication and reclamation program. The establishment or release of fast growing native plants is required, which will out compete any surviving exotic plants. Native plant seed and seedlings are becoming increasingly available for planting for rehabilitation, but limited number of species and the absence of well-developed establishment procedures often hinder their current use. Native plants do have native predators and require proper seed treatments to assure timely germination, thus their establishment will be more challenging than the commonly available alien plants. Native plant communities naturally reinitiate succession on many areas after exotic plants have been controlled when the soil seedbank remains intact. Constant surveillance, treatment of new unwanted arrivals, and rehabilitation of current infestations are the necessary steps to manage exotic plant invasion on a specific site.

Author’s Note: Use of trade names is for reader’s information and does not constitute official endorsement or approval by the U.S. Department of Agriculture to the exclusion of any suitable product or process.

Sources of Control Information

Books

Randall, J.M., and J. Marinelli, ed. 1996. Invasive Plants: weeds of the global garden. Brooklyn Botanic Garden, handbook #149. 111 p.

Articles and Reports

Bruce, K.A., Cameron, G.N., Harcombe, P.A., and Jubinsky, G. 1997. Introduction, impact on native habitats, and management of a woody invader, the Chinese tallow-tree, Sapium sebiferum (L.) Roxb. Natural Areas Journal 17:255260.

Derr, J.F. 1989. Multiflora rose (Rosa multiflora) control with metsulfuron. Weed Technology 3:381-384.

Dreyer, G.D. 1988. Efficacy of triclopyr in rootkilling oriental bittersweet (Celastrus orbiculata Thunb.) and certain other woody weeds. Northeast Weed Science Society Annual Meeting Proceedings 42:120-121.

Edgin, B., and J.E. Ebinger. 2001. Control of autumn olive (Elaeagnus umbellata Thunb.) at Beall Woods Nature Preserve, Illinois, USA. Natural Areas Journal 21:386-388.

Everest, J.W., Miller, J.H., Ball, D.M., and Patterson, M. 1999. Kudzu in Alabama: history, uses, and control. Alabama Cooperative Extension, ANR-65. 6 p.

Edwards, M.B., and Gonzalez, F.E. 1986. Forestry herbicide control of kudzu and Japanese honeysuckle in loblolly pine sites in Central Georgia.

Kline, W.N., and Duquesnel, J.G. 1996. Control of problem vegetation: a key to ecosystem management. Down to Earth 51:20-28.

Koger, T.H., and Stritzke, J.F. 1997. Influence of herbicide timing and mowing on control of sericea lespedeza (Lespedeza cuneata). Southern Weed Science Society Annual Meeting Proceedings 50:76.

Judge, C.A., Neal, J.C., and Derr, J.F. 2001. Postemergence control of Microstegium vimineum. Weed Science of America Annual Meeting Proceedings 41:47.

Miller, J.H. 1986. Kudzu eradication trials testing fifteen herbicides. Southern Weed Science Society Annual Meeting Proceedings 39:276-281.

Miller, J.H. 1988. Kudzu eradication trials with new herbicides. Southern Weed Science Society Annual Meeting Proceedings 41:220-225.

Miller, James H. 1998. Exotic invasive plants in southeastern forests. P. 97-105. In: Britten, K.O. ed., proceedings of the Exotic Pests of Eastern Forests, 1997, April 8-10, Nashville, TN. Exotic Pest Plant Council, Nashville, TN.

Miller, James H. 1998. Primary screening of forestry herbicides for control of Chinese privet (Ligustrum sinense), Chinese wisteria (Wisteria sinensis), and trumpetcreeper (Campsis radicans). Southern Weed Science Society Annual Meeting Proceedings 51:161-162.

Miller, James H. 1999. Controlling exotic plants in your forest. Forest Landowner 58:60-64.

Miller, James H. 2000. Refining rates and treatment sequences for cogongrass (Imperata cylindrica) control with imazapyr and glyphosate. Southern Weed Science Society Annual Meeting Proceedings 53:181.

Mullahey, J.J., and Colvin, D.L. 2000. Weeds in the sunshine: Tropical soda apple (Solanum viarum) in Florida – 1999. Institute of Food and Agricultural Sciences, Univ. of Florida, Gainesville, FL. 7 p.

Neal, J.C., and Skroch, W.A. 1985. Effects of timing and rate of glyphosate application on toxicity to selected woody ornamentals. Journal Amer. Society of Horticultural Science 110:860-864.

Nuzzo, V.A. 1991. Experimental control of garlic mustard (Alliaria petiolata (Bieb.) Cavara & Grande) in northern Illinois using fire, herbicide, and cutting. Natural Areas Journal 11:158-167.

Regehr, D., and Frey, D.R. 1988. Selective control of Japanese honeysuckle (Lonicera japonica). Weed Technology 2:139-143.

Szafoni, R.E. 1991. Vegetation management guidelines: multiflora rose (Rosa multiflora Thunb.). Natural Areas Journal 11:215-216.

Thomas, Jr., L.K. 1993. Chemical grubbing for control of exotic wisteria. Castanea 58:209-213.

Underwood, J.F., and Sperow, Jr., C.B. 1985. Control methods for multiflora rose (Rosa multiflora Thunb.) with metsulfuron methyl. North Central Weed Science Society Annual Meeting Proceedings 40:59-63.

Washburn, B.E., and Barnes, T.G. 2000. Postemergence tall fescue (Festuca arundinacea) control at different growth stages with glyphosate and AC 263,222. Weed Technology 14:223-230.

Washburn, T.G, and Washburn, B. 2001. Controlling tall fescue, common Bermuda, and bahia grass. Wildland Weeds 4:5-8.

Willard, T.R., Gaffney, J.F., and Shilling, D.G. 1997. Influence of herbicide combinations and application technology on cogongrass (Imperata cylindrica) control. Weed Technology 11:76-80.

Yeiser, J.L. 1999. Japanese honeysuckle control in a minor hardwood bottom of Southwest Arkansas. Southern Weed Science Society Annual Meeting Proceedings 52:108-111.

Manuals

Smith, Tim E. (editor). 1993. Missouri vegetation management manual. Natural History Division, Missouri Department of Conservation, Jefferson City, Missouri. 148 p.

Tennessee Exotic Pest Plant Council. 1996. Tennessee exotic plant management manual. TNEPPC, Warner Parks, Nashville, Tennessee. 118 p.

Newsletters

Southeast Exotic Plant Pest Council, 819 Cheryl Lane, Lexington, Kentucky 40504.

Magazines

Wildland Weeds, Florida Exotic Plant Pest Council, 3301 Gun Club Road, West Palm Beach, Florida 33406

Websites

• Alien Plant Database: www.bugwood.org
• Bugwood Network: www.bugwood.org
• California Exotic Plant Pest Council: www.caleppc.org
• Florida Exotic Plant Pest Council: www.fleppc.org
• Southeast Exotic Plant Pest Council: www.se-eppc.org
• Southern Research Station: www.srs.fs.us
• Southern Weed Science Society: www.weedscience.msstate.edu/swss
• USDA Animal and Plant Health Inspection Service’s Federal Noxious Weed Program: www.aphis.usda.gov/ppq/weeds
• USDA Natural Resources Conservation Service’s National Noxious Weed Program: dogwood.itc.nrcs.usda.gov:90/Weeds
• 
  Sources of Native Plants
  
  
• USDA Natural Resources Conservation Services’s Plant Materals Program: plant-materials.nrcs.usda.gov/

Selective Application Methods

Directed Foliar Sprays
Herbicide application by directed foliar spray is the most cost-effective method for treating most types of exotic species. With this method, herbicides are thoroughly mixed in water, often with a non-ionic surfactant, and applied to the foliage and growing tips of woody plants or to completely cover herbaceous plants. Foliar sprays are usually most effective when applied from mid-summer to late fall, although spring and winter applications have use on specific exotic plants. Selective treatment is possible as the applicator directs the spray to target plants and away from desirable plants. The addition of a water-soluble dye can assist in tracking treatment and indicate spray drift on desirable plants. Use of a dye is also helpful in training new applicators, but dyes are messy to use.

Directed sprays are usually applied with a backpack sprayer and a spray wand equipped with a full cone, flat fan, or adjustable cone spray tip. With these tips and spraying pressures of 20 to 30 pounds per square inch (psi), productivity can be maintained with only a few fine droplets that may drift to surrounding plants. Applications should be suspended during windy conditions to safeguard surrounding plants from damage by spray drift. A spray shield that attaches to the end of the wand can further minimize drift and a drift retardant can be added to the spray mixture to essentially eliminate drift.

Plants up to 6 ft tall can be treated with this equipment, while the addition of a commercially available wand extension can slightly increase height capabilities. Treatment of taller plants up to about 18 ft tall can be achieved by using higher spray pressures and by using straight-stream or narrow flat fan tips.

Directed foliar sprays are also applied using wands on hoses attached to spraying systems mounted on 4-wheeler ATV’s, trucks, or tractors. Also, a spray gun with a narrow flat fan tip is used by some applicators instead of a wand.

Stem Injection and Girdle-Treat
Tree injection, including the hack-and-squirt technique, is a selective method of controlling larger trees and shrubs (greater than 2 inches diameter) with minimum damage to surrounding plants. It requires that downward incisions are spaced around the stem and a measured amount of herbicide is applied into each of the incision cups-like cuts. Special tree injectors can be used to perform these two operations or a narrow-bit ax or hatchet or machete along with a spray bottle can be used in sequence to perform the hack-and-squirt method. Completely girdling the stem and applying herbicide to the girdle cut is another similar method that uses the herbicide less efficiently but is effective on very large stems and difficult-to-control species, called the Girdle-Treat Method. The herbicide should stay in the injection cut or on the girdle surface, because any herbicide on the bark is wasted. Furthermore, herbicides with soil activity that run or are washed to the soil can damage surrounding plants. Also, all herbicides can be transferred to untreated plants through root grafts and root exudates.

Tree injection treatments are most effective when applied in late winter and throughout the summer. Heavy spring sap flow can wash herbicide from incision cuts, making this an ineffective period.

Cut-Treat
Freshly cut stems and stumps of woody exotics can be treated with herbicide mixtures to prevent resprouting and kill roots, including canes and bamboos. Stems and stumps must be treated as quickly as possible after cutting. For spray applications, a backpack sprayer or utility spray bottle can be used. For small cut stems, a wick applicator or lab wash bottle can be used. A non-ionic surfactant should be added to the mix to aid in penetration, if permitted by the label.

For stumps over 3 inches in diameter, the outer edge should be completely wetted with the herbicide or herbicide mixture. The tops of smaller stumps are usually completely wetted and all cut stems in a clump should be wetted. Stumps that have remained untreated for over 2 hours should be treated with the basal spray mixture of herbicide, oil, and penetrant.

The most effective time for using the stump spray method is late winter and summer. Winter treatments are slightly less effective than growing season applications.

Basal Sprays
Full basal treatments require that the lower 12 to 20 inches of target woody stems be completely wetted on all sides with a oil-based spray mixture. Full basal sprays are usually effective in controlling woody stems less than about 6 inches in diameter or larger diameters of susceptible species. To apply this treatment, a backpack sprayer is used with a wand or spray gun fitted with a narrow-angle flat fan, cone, or adjustable tip. An appropriate wick applicator can also be used. Herbicides that are soluble in oil (mainly Garlon 4) are mixed with a commercially available basal oil, diesel fuel, or kerosene often adding a special penetrant. Some herbicides are sold ready-to-use with these ingredients (e.g., Pathfinder II and Pathway.

A modified method, streamline basal sprays, can control many woody species up to 2 inches in diameter, while trees and shrubs of susceptible species up to 6 inches in diameter can be controlled. To apply this treatment, a backpack sprayer is used with a spray gun and a low-flow straight-stream or narrow-angle spray tip. For controlling herbicide output to prevent waste, a pressure regulator is needed to maintain pressure below 30 psi. At these pressures, an effective reach of 9 ft is possible while bark splash is minimized. For treating stems less than 2 inches in diameter, apply the stream of spray up-and-down single stems for about 6 to 8 inches, or apply across multiple stems creating 2- to 3-inch-wide bands. Direct the spray stream at a point about 6 to 24 inches from the ground, to smooth juvenile bark. Stems that are thick barked or near 3 inches in diameter require treatment on all sides. Back-and-forth bands can also be sprayed on larger stems

Applications are usually make in late winter and early spring when leaves do not hinder spraying the stem, although summer applications are effective but more difficult. Applications should be avoided on hot days if an ester herbicide formulation is used because non-target plant injury may occur from vapor drift.

Soil Spots
Spots of soil-active herbicide (mainly Velpar L) are applied to the soil surface in grid patterns or around target woody stems. With this method, exact amounts of herbicide are applied to the soil surface at prescribed spacings specified on the herbicide label. This treatment is only effective on specific exotic plant species and usually only effective when applied in spring and early summer. Spots are applied to the soil surface by using a special spotgun, utility spray bottle, or a backpack sprayer with a spray gun equipped with a straight-stream spray tip.