Gerald T. Johnson
Natural Resources Program Manager
92 CES/CEVN
100 W. Ent Street, Suite 155
Fairchild AFB, WA 99011
(509)247-2313
DSN 657-2313

Fax: (509)247-2878
Email: johnsontg@mail.fairchild.af.mil

Everywhere you go there are weeds to deal with. Whether it is 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 has mandated a fifty percent reduction in pesticide use by the year 2000. Fairchild has been seeking out new ways to reduce pesticide use while at the same time controlling weeds.

Noxious weeds are any plants which when established are highly destructive, competitive, or difficult to control by cultural or chemical practices. Both state and county laws mandate that landowners control these weeds in order to inhibit their spread.

Fairchild Air Force Base occupies approximately 4,500 acres in eastern Washington State, ten miles west of Spokane, Washington. The native grassland, shrub land, aquatic and forested ecosystems of eastern Washington currently occupy only a small fraction of their original extent. As a result, many of the native species and natural communities that inhabit this region have become rare or are threatened with extinction. While much of the land that makes up Fairchild AFB has been significantly altered, some portions may exist in a condition that approximates the original landscape and contributes to the preservation of rare natural features.

The climate is relatively dry and mild. Annual precipitation is variable, but usually totals between 11.1 and 19.8 inches. Most precipitation falls in the winter with a slight spring precipitation peak in May and June.

Much of the undeveloped portions of the base are dominated by pasture grasses and associated agriculture weeds. These areas occupy uniform stands of introduced grasses. These old fields possess a low diversity of plants, although some aggressive native species are present.

An inventory of Fairchild AFB was conducted to determine the extent of infestation by noxious weeds. Sixteen species of noxious weeds were found. These species were found predominantly in unimproved areas, with lesser quantities in semi-improved areas.

Five noxious weed groups were identified as being the most serious and posed the greatest threat. These include:

The problem of a widespread infestation of noxious weeds in the unimproved area was compounded by the fact that over 300 acres of wetlands are found in the same area.

Fairchild was in a predicament. 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 neighbors criticized our continuing noxious weed problem. A fifty percent reduction in the use of pesticides was the goal and little progress was being realized.

A solution to this dilemma was anxiously sought. The 92^nd 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, which includes Pollution Prevention, Natural Resources and Compliance; the Grounds Quality Assurance Office; and the Base Entomologist came up with an innovative solution.

This solution was "Biological Control". Biological control is the intentional use of living organisms to reduce the population of a pest. It may include the use of insects, nematodes, mites, plant pathogens, and vertebrates. Often more than one agent is introduced on a weed. Each enemy detrimentally affects the weed to some degree. This effect may be obvious, such as when the plant is defoliated, or it may be subtle, such as when slight damage caused by the bio-control agent allows secondary organisms to inflict greater damage.

The majority of the noxious weeds in the United States are introduced without their natural enemies. Many of these weeds originally came from Europe and Asia. The secret to controlling these weeds with bio-controls is to go back to their native home and find the natural enemies.

Approximately thirty years ago, increased emphasis and funding was placed on the effort to find appropriate bio-controls for noxious weeds. The US Department of Agriculture (USDA), through the Agricultural Research Service (ARS) and the Cooperative Extension Service (CES) began doing extensive research on where the weeds came from and what natural enemies occurred in their native homeland.

The ARS conducts a complex procedure for locating, screening, releasing and monitoring bio-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.

When a weed is targeted for study, its native land is identified and scientists begin to check the literature, study the life cycle and identify natural enemies of that plant. If the plant is difficult to locate in its native environment, or does not attain the vigor, height or density that it does in North America, than it is considered to be a good candidate for biological control. Discovering potential biological weed controlling agents on the plant also assists in making this decision.

After the target plant is approved for study, a survey of its homeland is conducted and natural enemies associated with the plant are cataloged. The potential agents are reproduced, identified and tested to determine effectiveness. The organisms are than evaluated during the survey as passive feeders or as destructive to the target plant. Those that are destructive are further examined to determine other plant species they may damage. Those with limited host ranges become candidates for additional host specificity testing. Extensive host testing is carried out to assure that only the target plants are impacted by the bio-control agents.

After testing is complete, various petitions and permits are required before field releases 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 which has been tested.

Fairchild AFB identified seven specific noxious weeds which they wanted to attack using biological controls. These weeds were 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 & quadrifasciata), Stem gall flies (Urophora cardui), Seed eating weevils (Rhinocyllus conicus) and Leaf & Stem gall flies (Cystiphora schmidti).

In order to assure that steps were taken to comply with the National Environmental Policy Act (NEPA), an Environmental Assessment was prepared. In the course of preparing the document all of the neighboring landowners, in excess of 100, were notified of the proposed action and a public meeting was held. The response was overwhelmingly positive. Many of those attending were very interested and expressed an interest in implementing biological controls on their property. No negative comments or opposition was expressed.

Beginning in May of 1996 the program was implemented. Dr. Piper collected the various insects from sites which had previously been release areas for the various insects. The adult insects were collected and placed in cardboard containers. The insects were then delivered to Fairchild over the next two months, depending on the emergence of the insects at the release sites.

As the insects were delivered they were immediately released at predetermined sites within the unimproved area of the base. Each of the sites were identified and marked both on the ground and on maps. This was done in order to monitor the progress and success of the program.

The effects of the insects was apparent very quickly and dramatically. 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 approximately $30,000. The cost to treat the acreage with either spraying or insects was about the same. 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 done. This cost savings is estimated to be in excess of $30,000 per year. We will also be well on our way to meeting the 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 which will result in a 40% 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 bio-control populations increase, the weed population will gradually decrease and may be unnoticed by the land manager. Biological controls usually do not eradicate weed populations. They will only reduce the population and spread of the weed.

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 1996, Western Society of Weed Science, PO Box 10342, Helena, MT 59604

Dr. Gary Piper, Washington State University, Pullman, WA 99164

Biological Control of Weeds, Noah Poritz, 1418 Maple Drive, Bozeman, MT 59715