Invasive plants cost the U.S. economy more than $120 billion a year in crop, livestock, and property loss and damage and in control costs (Pimental and others In Press). Invasive plants are those which are introduced to an area where they are not native and subsequently negatively impact the �economy, environment, or human health� in that area (MIPN 2005). Unfortunately, the public remains unaware of the threat posed by many invasive plants because to them they are green and growing and appear to be a part of nature.

A History

Asian bush honeysuckles, like many other invasive plants, were introduced to the United States with good intentions. Three species of Asian bush honeysuckle were introduced to the U.S. in the 18th and 19th centuries:  Tatarian from western and central Russia in mid-1700s; Morrow's from Japan in 1875; and Amur from China in 1897. The three species are collectively referred to as the Asian bush honeysuckles.

Today, the Amur honeysuckle is the most abundant of the three species through most of Indiana, with Tatarian being more common in the northern counties. Imported into the U.S. by the U.S. Department of Agriculture�s former Section of Foreign Seed and Plant Introduction for its potential usefulness as an ornamental, Amur honeysuckle remained a relic of eastern botanical gardens and urban park plantings through the first half of the 20th century (Luken and Thieret 1996). In the 1960�s, the USDA Soil Conservation Service began promoting Amur honeysuckle as a conservation shrub for erosion control and wildlife plantings.

An improvement program was established to identify and propagate varieties producing large quantities of fruit. The result was �Rem-Red�, a variety of Amur honeysuckle that produces large quantities of bright red berries. In a 1981 issue of American Nurseryman, �Rem-Red� was touted for its superior qualities as an erosion control, wildlife food and cover, and landscaping shrub (Sharp and Belcher 1981).

Asian bush honeysuckle was widely planted in urban parks and other urban green space from the 1950s through the 1970s. State forestry and wildlife agencies and cooperative extension services throughout the east began promoting it through state nursery sales, plantings on public properties, in resource management plans, and in tree and shrub planting and wildlife management literature. Purdue's Department of Forestry and Natural Resources planted Amur honeysuckle along with autumn olive in experimental wildlife plantings on a number of its properties in the 1960s and 1970s.

In 1961, Lucy Braun noted in her Woody Plants of Ohio that it was only found in Hamilton County (Cincinnati, Ohio), �. . . where it is becoming abundant in pastures and woodlands� (Braun 1961). Finally, in the 1980s evidence of Amur honeysuckle�s extreme invasiveness became apparent to some ecologists and conservationists (Luken 1988, Swink and Wilhelm 1994). Its ecology and impacts on native forest vegetation in the Central Hardwood Region were extensively studied by a number of researchers (Deering and Vankat 1999, Gorchov and Trisel 2003, Hutchinson and Vankat 1997, and Luken and Mattimiro 1991).

Its Biology and Ecology

Asian bush honeysuckle spreads from its original plantings through birds feeding on its fruits and then defecating the seeds. Interestingly, some birds, like finches and cardinals, crush and digest the seeds, and thus are not responsible for spreading bush honeysuckle. However, robins and starlings (another exotic invasive species) were found to consume large quantities of bush honeysuckle fruit and deposit the intact seeds for later germination (Bartuszevige and Gorchov 2003).

Fortunately, bush honeysuckle seeds do not remain viable for long periods of time, but germinate the spring after being deposited in the soil. It spreads to open vacant land, open woodlands, fence rows, recently disturbed areas, and young second growth forest, favoring rich, moist, but not wet, sites. It first becomes established on forest edges and then spreads into the forest wherever there is sufficient light for seedling establishment. Where it becomes well established in the forest it may form a continuous, unbroken understory canopy, excluding most other native understory plants (Figures 1 and 2). It is not found in abundance in continuously cultivated, mowed, or pastured areas, or mature forest. Asian bush honeysuckle now occurs in virtually every county in Indiana and has an extensive range covering the entire northeastern U.S., south into Arkansas, Tennessee, and Georgia, and north into Ontario, Canada. The heaviest concentrations occur around urban areas where farmland was taken out of production ahead of urban/suburban encroachment. Highways and utility rights-of-way are corridors for spreading bush honeysuckle and other invasive species across the landscape.

In addition, many public lands located in rural areas contain old bush honeysuckle plantings which are now spreading to adjacent forest and vacant fields. Asian bush honeysuckle grows, flowers, and bears fruit under a wide variety of light conditions (Luken and others 1997). It attains its fastest growth rates in full sunlight. However, it tolerates deep forest shade.

Bush honeysuckle growth rates increase in direct proportion to increasing amounts of light resulting from forest canopy disturbances. Timber harvesting in forest stands with significant bush honeysuckle populations in either the understory or on the edges of the forest will only promote or increase the dominance of bush honeysuckle in the stand. This may adversely affect forest regeneration and most assuredly will harm the native forest herbaceous vegetation and shrub components and the wildlife dependent on them (Gould and Gorchov 2000).

Control

Numerous extension, government agency, and private conservation organization bulletins and websites provide information on Asian bush honeysuckle, including information on how control it. However, little experimental research specific to bush honeysuckle control has been published. Bush honeysuckle control methods are currently being studied by researchers at Purdue University's Department of Forestry and Natural Resources. Selecting an appropriate method for controlling bush honeysuckle depends in large part on:

1. The range of sizes of shrubs

2. The numbers of shrubs or size of area needing treatment

3. The operational environment (topography, whether in a forest, forest edge, fence row, or old field, forest density, availability of trails and access roads, etc.)

4. Availability of equipment, labor, and money

5. Desire to prevent damage to native vegetation Small infestations may be easily treated with hand control methods.

Due to its shallow-rooted nature, bush honeysuckle less than three feet tall is easily pulled out of the ground by hand. In fact, the most cost effective method of controlling bush honeysuckle is to prevent its establishment.

It is cheap and easy to control when few in numbers. Allow those few to reproduce and control costs quickly escalate. Landowners can learn to identify Asian bush honeysuckle and when it leafs out in the spring in their area. Because it is the first shrub to leaf out in the spring, well ahead of most native shrubs and trees, it is easy to spot. Every one to three years in the early spring, landowners may walk their property on �search and destroy� missions.

Because bush honeysuckle sprouts vigorously, simply cutting it down will not kill it. Without the use herbicides, repeated cutting throughout the growing season is necessary to exhaust the shrub�s root reserves and eventually starve it.

Foliar application of herbicides using a backpack sprayer is a cost effective method for controlling small quantities of bush honeysuckle ranging in size up to eight feet tall. Glyphosate (Roundup, Glypro, Clearout, others) and triclopyr (Garlon 3A or Garlon 4) are both effective foliar treatments on bush honeysuckle. Larger shrubs may be treated by cutting the shrub and applying an herbicide labeled for cut stump surface treatment. Some herbicides, primarily the ester formulation of triclopyr (Garlon 4), may be mixed with an oil carrier and applied to the base of shrub stems, 12 inches to 18 inches from the ground up on all sides according to stem diameter. This is called basal bark herbicide treatment. Herbicide costs for the basal bark treatment are higher than for the cut stump treatment, but labor costs are lower, making basal bark treatment a preferred option where cheap labor is unavailable. bush honeysuckle are most efficiently treated with large land clearing equipment such as a Kershaw hydroax (Figure 3). Vegetation management contractors, such as those which maintain utility rights-of-way, have such equipment. Expect to pay about $90/hr. plus a moving and set up fee. Sprouts require an appropriate foliar applied herbicide for final control of the bush honeysuckle. Some brush cutting equipment automatically applies herbicide to cut surfaces while cutting. For smaller jobs and smaller budgets, appropriately-scaled equipment is available (Figure 4)

Foliar application of appropriate herbicides is generally the most cost effective method of controlling bush honeysuckle across a broad range of shrub sizes, shrub densities, and operational environments. Forest edges and along trails can be sprayed with truck or tractor mounted high volume spray equipment (Figure 5). Four-wheel-drive tractors or log skidders allow high volume foliar herbicide application off road in a forest environment

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