by CELESTINE DUNCAN
Autumn olive is an invasive woody shrub or small tree that grows to about 20 feet in height.
The shrub is widespread in the eastern third of the United States and Ontario, Canada (Figure 1). Autumn olive is native to Asia and was introduced to North America around 1830 for ornamental use, soil stabilization, strip-mine reclamation, and food and cover for wildlife.
Autumn olive is one of the first plants to leaf out in spring and grows rapidly, leading to suppression of native plants. The shrub establishes in a wide range of habitats and has nitrogen-fixing root nodules that allow it to grow on nutrient-poor sites. The plant is commonly found invading open and early-successional woodlands, abandoned agricultural fields, and edges of streams and rivers.
Autumn olive and Russian olive (Elaeagnus angustifolia) share similar habitat and invasive characteristics; however, autumn olive is more widespread in the eastern half of the United States, and Russian olive is more prevalent in the West. A comparison of vegetative characteristics between autumn olive and Russian olive is available at: bit.ly/Autumn-Russian-Olive.
LEAVES are elliptical to egg-shaped; 2 to 4 inches long and ½ to 1¼ inches wide; dark green to grayish green on upper surface with dense, silvery scales on the underside; leaves are arranged alternately along stems and have untoothed, wavy margins. Photo, Mark Renz, University of Wisconsin.
FLOWERS are conspicuous clusters along twigs at the base of leaves, appearing early spring to early summer; creamy-colored to light yellow with silvery exterior; bell-shaped and aromatically fragrant; 0.3 to 0.4 inch wide. Photo, The Nature Conservancy.
FRUIT are ¼-inch silvery, juicy berries dotted with brown scales that ripen to red or pink when mature in fall; single-seeded fruit are borne on short stalks. Photo, Pennsylvania Department of Conservation and Natural Resources, Bugwood.org.
There are several management options for autumn olive, depending on tree size, density, and environmental constraints. The following information discusses effectiveness of various management methods. (For detailed information on controlling Russian olive, go to bit.ly/saltcedar)
Small trees that are not well established can be removed with a weed wrench or dug with a spade when soil is moist. Digging must remove the entire root system, so the plant does not resprout.
Larger trees can be removed with a tractor, skid steer, or backhoe. This will cause significant disturbance, and follow-up management will be needed to restore the site to minimize soil erosion and invasion of other non-native plants. Roots remaining in the soil will likely resprout, so a foliar herbicide treatment will be necessary to stop reinvasion.
Cutting the shrub at the base will cause prolific sprouting and increase the number of stems if a herbicide is not applied to the cut surface. An effective strategy for controlling autumn olive is to kill both the above-ground portion and the root system, which eliminates the potential for resprouting. This is most effectively achieved through herbicide use.
Selective systemic herbicides will effectively control autumn olive. Sites will need to be monitored for possible resprouts and new seedlings that germinate following application.
Results of field trials conducted in Virginia, Pennsylvania, and Indiana show that Vastlan® herbicide (Garlon® 3A), or Garlon® 4 Ultra herbicide alone or in combination with Milestone® herbicide, will control autumn olive without injury to desirable understory grass vegetation. The addition of Milestone improves autumn olive control and also provides broadleaf weed control on species such as knapweed and thistle. Desirable plants remaining on the site will compete with autumn olive resprouts and germinating seedlings, decreasing the potential for reinvasion. There are several herbicide application options described below, depending on tree size, density, and management equipment available.
I. High-Volume Foliar Treatments to Individual Trees (smaller than 6 feet in height)
Foliar spraying is a method of control in which herbicide is sprayed directly on the leaves. Herbicide application needs to occur after the plant is in full leaf and before the onset of fall color in order to maximize effectiveness.
Herbicides are generally applied to wet the leaves, but not to the point of runoff. Treatments can be made to autumn olive shrubs smaller than 6 feet in height. It is important to calibrate your equipment to determine the amount applied per acre, including application made with a backpack sprayer or hand gun from a main tank. Typically, about 100 gallons per acre (GPA) are sprayed when “spraying to wet” without any runoff from the leaves. At an application volume of 100 GPA, mix 7 fluid ounces (0.05% v/v) of Milestone® herbicide and 4 quarts (1%) of Garlon® 4 Ultra herbicide in 100 gallons of water with 1 quart (0.25% v/v) of a non-ionic surfactant.
For small infestations and follow-up spot treatments, mix 1.3 fluid ounce of Garlon 4 Ultra with 2.1 cc’s of Milestone (use a syringe to measure the Milestone) in one gallon of water with a non-ionic surfactant, and spray to wet foliage. The addition of Milestone to the mix will improve autumn olive control and will also control associated noxious and invasive weeds.
II. Foliar Treatments to Resprouting Autumn Olive after Mowing or Cutting
Autumn olive will resprout following cutting, mowing, or shredding operations. Wait at least six months after cutting, until resprouts grow to 3 to 4 feet tall, before applying the herbicides. This allows time for plants to regrow and develop adequate leaf area for more herbicide uptake from a foliar application. This may mean the application will need to occur the year after cutting, or, at least, in late summer after a previous winter mowing. It may also occur earlier in the spring of the same year.
Autumn olive resprouts can be controlled with a foliar application of Milestone® at 7 fluid ounces per acre (fl oz/A) plus Garlon® 4 Ultra at 4 quarts per acre (qts/A) with a non-ionic surfactant. See the high-volume foliar treatment above for mixing guidelines.
III. Low-Volume Basal Bark Applications
This treatment method is effective on trees with stems up to, but not larger than, 6 inches in diameter (Figure 2). The herbicide application can be made any time of year, including winter months, except when the bark is wet or frozen, or frost is present on stems. Applications are easier on grazed sites or during late fall to early spring when there is little foliage to intercept the spray. Another advantage to treatment this time of year is that many desirable plants are dormant, and selectivity can be improved. For best results, herbicide applications should be avoided during rapid growth of autumn olive in the spring.
A mixture of Garlon® 4 Ultra in an oil carrier is very effective for low-volume basal bark applications. An oil carrier ensures good coverage and herbicide absorption through the bark. The recommended concentration of Garlon 4 Ultra is 20% (see Table 1 for mixing recommendations).
Be sure to adjust the sprayer nozzle to deliver a spray that matches the size of the stem (use an adjustable solid cone nozzle). Spray the herbicide mixture lightly but evenly (similar to using spray paint) on the plant’s stem or trunk, from ground level up to 12 to 15 inches, and on any exposed root flares (Figure 2). Apply the mixture to all sides of every stem, but not to the extent that runoff and puddling occur at the crown or root collar. Autumn olive with old, rough bark may require individual stems to be treated from ground level to a height of about 15 to 18 inches.
Spray solutions are made with oil. Use oil carriers such as basal oils, diesel, kerosene, seed oils, or other oils with instructions for basal and cut-stump applications. Precaution: Soil oils are more viscous at low temperatures and harder or impossible to use in cold temperatures. Herbicides and basal oil need to be registered or accepted for use on the type of site where the treatment occurs.
IV. Basal Cut-Stump and Cut-Stump Application
Basal cut-stump treatments involve cutting six inches above the ground level, followed by herbicide application (Figure 3 and 4). Apply the herbicide solution (Table 1) to the sides of the stump, including the root collar area, the outer portion of the cut surface (cambium), and any exposed root flares (Figure 4) until thoroughly wet but not to the point of runoff. Avoid cutting followed by herbicide application during heavy sap flow, since this can interfere with penetration of oil-based basal mixes and decrease control. Heavy sap flow can also carry the herbicide mixture off the stump, resulting in poor control. While it is customary to treat soon after cutting, applications may be made any time after cutting (for example, cut in winter and treat the following spring), but should occur before resprouting.
Cut-stump treatments involve cutting the tree close to the ground and applying herbicide only to the exposed cambium (Figure 3). Cut-stump treatments are very effective for controlling autumn olive and can be used any time of the year as long as the herbicide does not freeze when applied, and the tree is not frozen. When using Vastlan® herbicide cut stumps should be treated immediately (within 30 minutes) after cutting. When using Garlon® 4 Ultra herbicide, applications can be made up to one week after cutting, but before resprouting begins (Table 2).
Monitor autumn olive that has been manually removed or treated with herbicide for at least two years to determine if complete control has been achieved. Shrubs that resprout or are not completely killed by the first treatment will require a follow-up treatment. Label recommendations should always be followed to maximize the potential for successful control.
Burch, Pat. Field Scientist (retired). Dow AgroSciences.
Dow AgroSciences. Unpublished field trial data.
EDDMapS. 2019. Early Detection & Distribution Mapping System. The University of Georgia — Center for Invasive Species and Ecosystem Health. Available online at www.eddmaps.org/
Munger, Gregory T. 2003. Elaeagnus umbellata. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available online
www.feis-crs.org/feis/ [2018, January 1].
Published April 2018; reviewed and updated June 2019
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