by CELESTINE DUNCAN
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. Russian olive was introduced into North America as an ornamental in the early 1900s, and later planted extensively in windbreaks in the western U.S. 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. Seedlings and young sprouts can be effectively removed by hand or mechanical pullers when the soil is moist. On larger trees, most non-herbicide management methods (bulldozing, mowing, brush-cutting) are not effective unless the root crown is removed or all re-spouts are treated with herbicide or continually cut. Burning is not an effective control technique due to re-sprouting. There are no biological control agents for Russian olive.
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. For information on late-spring and summer foliar treatments on Russian olive, go to bit.ly/saltcedar.
DORMANT-SEASON MANAGEMENT WITH HERBICIDES
Selective systemic herbicides will control Russian olive; however, it is not a one-time treatment and sites will need to be monitored for re-sprouts and new seedlings following application.
Cut Stump Applications
Cut stump treatments (Figure 1) 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 applying Vastlan® specialty herbicide, cut stumps should be treated immediately, or within 30 minutes following cutting. When using Garlon® 4 Ultra specialty herbicide, applications can be made up to one week after cutting but before re-sprouting begins (Table 1).
Thoroughly spray the outer 2 inches of the top of the stump. Apply herbicide mixture in a continuous ring between the bark and the wood of the stump. If the bark is torn away from the stump, be sure to treat down the side to form a continuous ring around the bark since coverage and uptake is essential for root kill.
Basal Cut Stump Applications
Basal cut stump applications involve cutting approximately six inches above the ground level and treating both the bark and exposed cambium (Figure 1). Use 20 to 30% v/v Garlon 4 Ultra for basal cut stump applications (Table 2), and spray the sides of the stump including the root collar area and the outer portion of the cut surface (the cambium) until thoroughly wet, but not to the point of runoff or so that puddling occurs at the crown or root collar. The herbicide treatment is effective when applied up to one week after cutting but before re-sprouting.
Low Volume Basal Bark Applications
This treatment method can be used on trees with stems up to but not greater than 6 inches in diameter (Figure 2). The herbicide application can be made any time of the year, including winter months, except when the bark is wet, frozen, or frost is present on stems. Applications are easier from 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 Russian 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 to 30% (see Table 2 for specific recommendations). The lower rate can be applied on younger trees with smooth bark.
Be sure to adjust the sprayer nozzle to deliver a narrow spray. 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. Apply the mixture to all sides of every stem, but not to the extent that runoff and puddling occurs at the crown or root collar. Russian olive with old, rough bark may require each stem to be treated higher up the stem (15 to 18 inches) compared to plants with smooth bark (12 to 15 inches). Larger stem diameter trees may require retreatment.
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State restrictions on the sale and use of Garlon 4 Ultra specialty herbicide 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.