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A Serious Weed: The Russian Olive

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By Ron Patterson
Utah State University Agriculture Agent

Weeds are everybody’s problem.

Russian olive is not a native plant and is considered an invasive species throughout the western United States and Canada. In Utah it is on the noxious weed list as a class IV weed. Class IV weeds are illegal to sell or propagate in the state, but this response will not be enough. In order to keep this plant from continuing to degrade our beautiful environment, everyone needs to take an active role in its eradication.

Russian olive (Elaeagnus angustifolia), once touted as a great habitat preservation plant, has become a habitat pariah, especially in Utah’s sensitive arid and riparian environments. It is choking out native plants and creating monoculture Russian olive stands. Research indicates Russian olive monoculture stands actually decrease wildlife diversity. Waterways, birds and other wildlife spread the seeds to other locations.

Russian olive also reduces the available feed in pastures. In one heavily grazed pasture where I was doing control research, I measured the area below individual Russian olive trees that was not being grazed by livestock or wildlife and found that the unused pasture averaged 60 percent of the area under the dripline of the tree. It’s even worse when they grow in clusters or groves, as Russian olives shade out the understory growth and, due to their vicious thorns, make it very difficult for animals to utilize any of the feed under the grove of trees. So, while it is true that some livestock and wildlife do eat the olives, the disadvantages far outweigh the advantages.

Russian olive is not yet a serious problem in Morgan County. But it will be much less expensive to take care of them now, before they start to harm the environment. If you have Russian olives on your farm or in your yard, remove them while they are still manageable.

Since 2005 I have been working with Emery County Extension Agent Dennis Worwood to find an answer for the habitat takeover by Russian olive. Two absolute things we have learned from our research are:

1) The process to kill Russian olive, any time of the year, is quite simple.

2) The work required to kill Russian olive is quite difficult.

Russian olive control requires more than just mechanical removal. A common saying in East Central Utah is, “When you tear a Russian olive out of the ground, all you have done is invited 100 Russian olives to the funeral, and they’re angry.” The resultant sprouts (crown suckers and root suckers) are difficult to kill. Mechanical removal, which works well on evergreens such as pinion pine and juniper, does not work on Russian olives and many other deciduous trees. Either herbicide application or repeated cultivation is required.

So, while we are continuing our research into Russian olive control techniques, we have not been able to get around the fact that we need to get “up close and personal” to be effective. One thing we have learned is that Russian olive is very susceptible to the herbicide glyphosate. It seems to translocate through the system better than the other herbicides we have used.

The most effective treatment technique is cut-stump herbicide application with glyphosate. Here are the guidelines:

• Cut tree to within 18” of the ground.

• Cut all branches off at the same level to avoid nicking or undercutting a branch.

• Be sure the cut is quite level so herbicide won’t run off.

• Brush any sawdust or dirt off the cut stump.

• Treat the outer growth rings (sap wood) to get herbicide drawn down into the roots.

• Application rate is 1cc herbicide (41 percent glyphosate) per inch of trunk diameter. (Don’t dilute it if the label allows it.)

• Treat all the way around the stem.

• Be sure to treat each stem.

To make application of the herbicide accurate, I use a livestock dosage syringe and set it to 1 cc per click. A YouTube video on this application method can be found at: http://www.youtube.com/watch?v=bN0HfFc2e-4.

This application method has given us nearly 100 percent control every month of the year. It is slow, difficult work. But once it is done, the control is very good. While other methods may initially seem faster, coming back to re-treat sucker growth ends up taking more time in the long run. Regardless of your treatment method, follow-up control activities will be required. Seed, which remain viable for about three years, will germinate and some roots may produce suckers.

Removing all Russian olive trees in Morgan County to avoid them overtaking our native habitat is a wise action. This would also keep us from becoming a seed source for other counties and communities around us. Every one of us needs to be responsible for the weed issue. Eradicating Russian olive from Morgan County is a good place to start.

Ron Patterson is the Utah State University Agriculture Agent in the Morgan and Weber County Extension Offices. He can be reached at 801-829-3472 or 801-399-8201. Utah State University is an affirmative action/equal opportunity institution.

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