​By Leah Kleiman

​Amur honeysuckle (Lonicera maackii) is a perennial shrub native to temperate Asia and is invasive in the Midwestern United States. It now infests many savannas and woodlands and is difficult to eradicate.  

​Bill and Susan Kleiman and I are co-authors of a study recently published in the journal Ecological Restoration, titled “The Successful Control of Lonicera maackii (Amur honeysuckle) with Basal Bark Herbicide” (http://er.uwpress.org/content/36/4/267.full.pdf+html). Our study looked at the efficacy of basal bark application, where a mineral oil solution of herbicide is sprayed in a 6-inch band on the bark without cutting the plant. Our study found 100% mortality with basal bark treatment.

​A variety of other treatment methods are used to battle honeysuckle. Manual pulling works well on small individuals in soft ground, but becomes impossible with larger sizes. Cutting and treating the stumps with herbicide is effective, but very time-consuming. We recommend the cut-and-treat method for sensitive high-quality areas. A foliar spray of herbicide is effective and efficient, but will have much more off-target damage and can only be used in the growing season. Fire is a useful tool in keeping brush at bay, but it will only top-kill shrubs. The basal bark method is efficient, effective in all seasons, and has minimal off-target damage. 

Some things to keep in mind: 1) Re-treating is important for success. One treatment is not enough. Some shrubs will inevitably be missed, and yearly recruitment will occur until the seedbank is exhausted. 2) Honeysuckle treated in the dormant season may still leaf out and die later in the growing season. So if you notice this, it does not mean that your treatment has failed, but rather that you need to check back at a later date (typically late summer/fall).

​Our study concludes that basal bark treatment paired with regular fire is the optimal way to eradicate honeysuckle invasions. For more information on treating honeysuckle with basal bark, see the February 3, 2019 blog post “A Study on Controlling Amur Honeysuckle (Lonicera maackii)” by Kaleb Baker.

​By Kaleb Baker

Amur honeysuckle (Lonicera maackii) is an invasive shrub that flourishes along forest edges and in open woodlands such as those at Nachusa Grasslands. Amur honeysuckle shades out native flora with its early leaf-out and prolonged leaf retention, and when left uncontrolled, can produce a near monoculture, threatening biodiversity.

Land stewards everywhere have implemented a variety of different eradication methods, including hand pulling, cut-and-treat with herbicide, foliar-applied herbicide from backpacks or helicopters, basal bark herbicide treatments, and prescribed fire. Continuous treatments and monitoring are needed to eradicate Amur honeysuckle, making the cost, effort, and time requirements of controls important.

Knowing the efforts we go through to manage honeysuckle, as well as the amount of conjecture surrounding the best practices, I worked with my advisor Dr. Nick Barber to study how effective basal bark treatments and prescribed fire are at controlling honeysuckle., I decided to study how effective basal bark treatments and prescribed fire are at controlling honeysuckle. Basal bark and fire are regularly-used control methods at Nachusa. Basal bark treatments involved spraying a 20% solution of triclopyr herbicide around each plant’s base from a backpack, which was both quick and easy. In this study I included 800 individually-marked Amur honeysuckle at 5 different sites within Nachusa Grasslands and Franklin Creek State Natural Area. Basal bark treatments were applied in fall 2017, winter 2018, early spring 2018, and late spring 2018 to see if the season of application affected the mortality of honeysuckle or the extent of damage to non-target flora. Prescribed fire was administered to half of each of the 5 sites in spring 2018. I then checked mortality in the early fall of 2018 to allow the honeysuckle time to either drop its leaves and regrow them (falsely dead) or to retain its leaves for an extended period of time before dying (falsely alive).

I found that basal bark applications were equally effective at killing Amur honeysuckle, regardless of treatment timing. The combined mortality rate of herbicide treatments was 98.4% across all herbicide treatment seasons, compared to a 2.5% mortality with no basal bark treatment. Prescribed fire did not impact mortality positively or negatively.

​​I was lucky to receive a grant from the Friends of Nachusa Grasslands where I will be able to return in May 2019 to resample the off-target vegetation quadrats to evaluate how quickly the flora recover from the various treatments.
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From my current results, I highly recommend using basal bark treatments to control Amur honeysuckle for all but the highest quality of areas. The speed and ease of use allow managers to cover large swaths of invaded areas across fall, winter, and spring seasons. The standing dead material from the honeysuckle can be reduced with a masticator or brush mower in the non-growing season or with regular prescribed fire, which should be implemented anyway.

Kaleb Baker is a Master's Candidate at Northern Illinois University, focused on natural areas management practices, and current Stewardship Committee Chair for Franklin Creek Conservation Association.

Native oak-hickory savannas and woodlands in the region are disappearing along with bird species that depend on the open structure: red-headed woodpeckers, great crested flycatchers, and eastern bluebirds. Native wildflowers such as kitten tails, wild hyacinth, prairie lily, and starry campion along with grasses such as bottle brush rye, woodland brome, and long-awned wood grass will not grow in heavy shade. And there are the native shrubs: hazelnut, American plum, hawthorn, and Iowa crabapple! None of these tolerate shade either.

I encourage you to read up on oak woodlands, then take a hike. Explore the Stone Barn Savanna  and see how we are doing. It’s a work in progress and sometimes messy, but we see the native oak savanna dependent plants and animals are thriving.
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Here are some great websites that discuss oak savannas:
Pleasant Valley Conservancy—Oak Savannas
​Last of the Oak Savannas Survive in Minnesota
​What is an Oak Savanna?

Written by Susan Kleiman, a Nachusa volunteer.
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By Mark Jordan

​It is easy to spot and identify in late autumn.  The tall deciduous trees, the oaks, the hickories and others, have but a few brown leaves still clinging to their skeleton frames.  Below, on shorter plants, abundant leaves remain green.  A drive in the country reveals this late season green plant growing at the edge of a woodlot, deep in a forest or in abandoned fields.  It is in the fall that its abundance becomes most visible. It is exotic and invasive bush Honeysuckle.

Nonnative Honeysuckles such as Amur Honeysuckle, Showy Fly Honeysuckle, Common Fly Honeysuckle and others were introduced into the United States from Eurasia more than 100 years ago.  They were brought into new habitats for ornamental reasons, for erosion control and for wildlife cover.  In the absence of repeated fires and in grazed and disturbed wooded areas the exotic Honeysuckles have reproduced rapidly and spread widely.

There are woodland and savanna areas now in Nachusa Grasslands where the Honeysuckle has become abundant over many decades and is disruptive to the native ecosystems.  These multi-stemmed  bushes can grow up to twelve feet tall and form very thick shrub layers that prevent the growth of native species by decreasing the amount of light reaching the forest floor and by using up nutrients and water in the soil.  Honeysuckles are considered an allelopathic species as they release chemicals into the soil that inhibit the growth of native species.  Birds that may build nests in Honeysuckle are more susceptible to predation because the Honeysuckle branches are nearer the ground than native bushes.   The abundant berries, while high in carbohydrates, do not produce the fats and nutrients needed by migrating birds in the fall.

I have been a steward of the East Tellabs Unit at Nachusa Grasslands since 2011.  With the help of many volunteers, other stewards and the Nachusa crew, we have cut and treated thousands of Honeysuckle plants of all sizes.  It is rewarding to use a pair of loppers or a saw to cut a plant near its base and treat the stump with a chemical to kill the Honeysuckle and prevent resprouting.  The forest floor is exposed and sunlight may reach it for the first time in years.  Other methods of attacking this invasive plant include chemically spraying the leaves, applying chemicals to the base of the plant and seasonal fires. 

The work to decrease the Honeysuckles continues. A few hours working among the Honeysuckle can leave one tired, sweaty, sore, scratched and covered in burrs.  Yet the tired and sore will go home feeling proud for doing a necessary task that makes a difference in the diversity and ecology of the woodlands and savannas. Each Saturday a Nachusa steward leads a volunteer workday.  You might collect seeds, you might pull weeds, you might pile deadfall, or you might cut, treat, stack and burn Honeysuckle. 

Text and Photography by Tellabs Steward Mark Jordan