Everywhere you go, there are weeds to deal with. Whether it's the dandelions in the commander's yard or an obnoxious thistle on the back forty, we all have weeds. In the past it presented little problem to attack these invaders. Call the base entomologist or a local contractor to come and spray the area. That has all changed now. Using 1993 as a base year, the Air Force mandated a fifty percent reduction in pesticide use by the year 2000. Fairchild afb used that requirement to seek new ways to reduce pesticide use while at the same time controlling weeds and enhancing native biodiversity.

Location and Land Condition

Situated 10 miles west of Spokane, Washington, Fairchild Air Force Base occupies approximately 4,500 acres in eastern Washington State. Much of the undeveloped portions of the base are dominated by pasture grasses and associated agriculture weeds.

Impact on the Military Mission

Noxious weeds were degrading the natural habitat of Fairchild afb, especially in unimproved areas, including over 300 acres of wetlands. Fairchild was in a predicament as weeds continued to spread in spite of spraying, wetlands posed a problem when using herbicides so buffer strips were set aside to assure the spray didn't reach the water, and the off-base neighbors criticized the base's continuing noxious weed problem.

The Solution Using Biological Controls

The 92nd Civil Engineering Squadron, which is responsible for the maintenance of grounds and infrastructure on the base, brought together a group of experts on the base to attack the problem. The environmental flight and the base entomologist decided to try an innovative solution: “Biological Controls.” A biological control can involve intentionally using living organisms to reduce the population of a pest species. These may include microscopic plant pathogens, insects, nematodes, mites, and vertebrates. Often more than one agent is introduced to control a specific weed. The effect of the biological control agent may be obvious, such as when the plant is defoliated, or it may be subtle, such as when slight damage caused by the biological agent allows secondary organisms to inflict greater damage.

The U.S. Department of Agriculture, through the Agricultural Research Service (ARS) and the Cooperative State Research, Education, and Extension Service (CSREES) , conducts a complex procedure for locating, screening, releasing and monitoring biological control agents of weeds. Every effort is taken to ensure that introduced biological weed control agents are limited to specific hosts and do not threaten other plants. Precautions are also taken to ensure that the introduced agents are not diseased. After testing, various petitions and permits are required before field releases of bio-controls can be made. Every step of the process is closely monitored to ensure that the bio-controls are host-specific, pathogen free, disease free and that the agent to be released is the exact specimen that has been tested.

Implementation

Fairchild afb identified seven major noxious weeds for biological control: Russian Knapweed, Spotted Knapweed, Diffuse Knapweed, Canada Thistle, Musk Thistle, Plumeless Thistle, and Rush Skeletonweed. Working closely with Dr. Gary Piper, Washington State University, several specific agents were identified which would work on the identified weeds. These controls included Seed Head Gall Flies (Urophora affinis and quadrifasciata), Stem Gall Flies (Urophora cardui), Seed Eating Weevils (Rhinocyllus conicus) and Leaf and Stem Gall Flies (Cystiphora schmidti). http://www.aenews.wsu.edu/June02AENews/Knapweed/Knapweed.pdf

In preparation for this project, Fairchild afb conducted an Environmental Assessment as required by the National Environmental Policy Act (nepa).More than one hundred neighboring landowners were notified of the proposed effort and invited to participate in a public meeting to review the proposed action. The response was overwhelmingly positive and many of the landowners attending expressed an interest in implementing biological controls on their property. The public review yielded no negative comments or opposition.

Results

Dr. Piper implemented the program in May 1996 by collecting various insects from sites where they had previously been released. During the following two months he delivered the insects to Fairchild afb and immediately released them at predetermined sites within the unimproved area of the base. Each of the sites was identified and marked both on the ground and on maps to ensure accurate monitoring of the progress and success of the program.

We achieved early and dramatic results. Many of the thistles quickly developed stem galls, flowering seed heads were full of larvae, and leaves on the plants showed evidence of insect damage. Approximately 300,000 insects were released at a cost of $30,000, an amount about equal to treating the same acreage with traditional chemical pesticides. The big cost savings will come during the ensuing years when the insects reproduce naturally. They will continue to attack the weeds and no spraying will be required. And, the elimination of pesticides contributed significantly to meeting the Air Force pesticide reduction goals.

In all, Fairchild treated over 710 acres of unimproved ground with biological controls. We eliminated spraying near 300 acres of high-quality wetlands. Approximately 1,200 acres of ground was eliminated from our spraying program; that will result in a 40 percent decrease in pesticide sprayed to control noxious weeds.

The main disadvantage of biological weed control is that it often takes many years for the populations of the introduced agents to increase to levels that permanently decrease the pest plant populations. A limited number of eggs are laid by insects and initial population build-up appears slow. However, insect numbers increase exponentially. As biocontrol populations increase, the weed population will gradually decrease and may be unnoticed by the land manager. Biological controls usually do not eradicate weed populations. Rather, they will mainly reduce the population and thus the spread of the weed.

Conclusion

Use of biological agents is only one tool in the fight against noxious weeds. Multiple control methods are important when implementing any management system. Each installation needs to take an integrated approach when attacking noxious weeds and other pests. An integrated pest management plan should be prepared in order to ensure a coordinated approach is taken.

Biological Control of Weeds in the West, February 19 (Western Society of Weed Science, P.O. Box 10342, Helena, Montana, 59604)
http://www.weedcenter.org/management/bioweed-credit.pdf