What is a biological control?

 The following excerpts were taken from Forest Health Technology Enterprise Team, Technology Transfer

Biological Control

Biology and Biological Control of Leafy Spurge

Authors:  Dr. Rob Bourchier, Dr. Rich Hansen, Dr. Rodney Lym, Dr. Andrew Norton, Dr. Denise Olson, Carol Bell Randall, Dr. Mark Schwarzlander, Dr. Luke Skinner

(Our thanks to the team for allowing us to use the following material.)

**Biological control of weeds is the deliberate use of living organisms to limit the distribution and abundance of a target weed. 

Generally non-native plants are introduced without their natural enemies, the complex of organisms that feed on the plant in its native range.  This lack of predation is one reason non-native plant species become major pests when introduced outside of their native range.

Natural enemies can damage or destroy a weed’s flowers, seeds, roots, foliage, or stems.  This damage may kill the plant outright, reduce weed vigo and reproductive capability, or help cause or promote secondary infection from pathogens-all of which reduce the weed’s ability to compete with other plants. 

The aim of biological control is to reunite host-specific natural enemies with the target invasive plant to reduce the weed’s impacts and restore at least a part of the ecological balance present in the invasive plant species’ native range. 

          Advantages of bio-control:  biological control is selective against a specific weed or closely related group of weeds, can provide long-term control, and is thought to be less damaging to the ecosystem than some other weed management, can provide long term control, and is thought to be less damaging to the ecosystem than some other weed management methods.  Once established at a site, biological control agents are self-perpetuating and will continue to attack the target weed year after year.  Most biological control agents are able to disperse to new target weed patches, even in difficult terrain.  Over the long term the ability of biological control agents to provide continuous weed suppression and to move to new infestations as they become established make them a cost-effective weed management tool.

          Disadvantages of bio-control:  uncertainty about whether the biological control agents will effectively suppress the target weed to desired levels, the long time that might elapse before impacts are observed, and the risk of adverse non-target impacts on unintended plant species.  Biological control agents can not be removed from the ecosystem once they are established, so they are and must be selected carefully and studied extensively before they are introduced. 

 Natural enemies used in classical biological control of weeds include insects, mites, nematodes and fungi.  Beetles, flies and moths are among the most commonly used insects.  To be considered for release in the United States, biological control agents must feed and develop only on the target weed, and in some cases, on a few closely related plant species.  A potential biological control agent’s life cycle should be closely matched or synchronized with that of the target weed. 

BIOLOGICAL CONTROL ASSISTANCE  TO THE LWRCWMA

 In 2006 a biological control specialist position was finalized by the Bureau of Land Management (BLM) and the Idaho State Department of Agriculture (ISDA).  Joe Milan was chosen for that position.  Joey is a Boise, Idaho native who graduated from Albertson College of Idaho with a BS in Biology and began his career with the BLM in 2001.  In 2002, he entered a graduate program at the University of Idaho where he completed his MS in Entomology.  For his Master’s Thesis, he did research on the impacts of biological control agents for rush skeletonweed.  Upon completion of his MS he was hired for this interagency position.  At the present he serves as the interagency coordinator for biological control, assisting weed control practitioners in their Integrated Weed Management approach by providing technical assistance and monitoring of past releases as well as organizing new collections and additional potential releases. 

 The LWRCWMA relies upon the Nez Perce Bio-Center located in Lapwai, Idaho.  Paul Brusven serves as the Bio-Control Coordinator for the tribe.  He coordinates efforts to rear and disperse approved bio-control agents (insects) that attack noxious and invasive weeds that persist across thousands of acres in Idaho and the Pacific Northwest States.  The Nes Perce Bio-Center has been a great asset for many years assisting Washington County with our biological needs.

The following story was featured in the Washington County Weed Warriors newsletter, September 1, 2007 issue.

 Creating a successful biological control project

By Joey Milan, BLM/ISDA

 Biological control is a unique weed control practice because the goal is drastically different than that of mechanical, chemical, or cultural control.  With biocontrol, you as a landowner or land-manager are acknowledging that you will not be able to eradicate a weed from an area and, instead, you are prepared to live with it if its impact can be brought down to a negligible level.  Given this situation, how do we define a level of occurrence that is acceptable and what other factors are involved in reaching that acceptable level-in essence, how do we create a biological control success story?

 Many of you are familiar with the biocontrol agents for leafy spurge, purple loosestrife and Dalmatian toadflax and how successful they have been in your area and around the rest of the west.  Where these agents have been successful, a common theme is contributing to their success.  Plant competition using desirable replacements for these weeds is critical in establishing a system that will be able to maintain its “acceptable” weed level over time.  Often times, the desirable replacements are waiting for the wed population to decline in the seed bank but sometimes this isn’t the case.  When the weeds have been present for a significant amount of time, the desirable seeds on site may have lost their viability and an additional push may be needed.  

 Biocontrol is a great weed control method to use with revegetation.  When putting the insects on the weed patch you wish to control, bring along some desirable seed as well, especially in monotypical stands where seed banks might be limited.  If the land likely already has a viable seed bank, try to limit disturbance in the area to give desirable seeds a chance to germinate.  This will help ensure that your biological control project will be a successful one.