Jump to main content.

Evaluation of Colorado Weed Biological Control Programs

Project Contact

Lynda Olin, Office of Sponsored Programs
408 University Services Center
Colorado State University
Fort Collins, CO 80523-2002
970-491-6904
970-491-6147
Lynda.Olin@research.colostate.edu

Project Directors

Andrew Norton
Department of Bioagricultural Sciences and Pest Management
Colorado State University, Fort Collins, CO
970-491-7421
970-491-3862 (fax)
Andrew.Norton@Colostate.edu

Eric Lane and Dan Bean
Colorado Department of Agriculture
Noxious Weed Management Program and State Biological Control Insectary

Richard Hansen
USDA-APHIS-PPQ
National Weed Management Laboratory
Fort Collins, CO

Purpose Statement

We will continue to evaluate the efficacy of weed biological control releases in order to improve program success and reduce herbicide use in Colorado. By examining agent establishment rates and their impact on targeted weeds we will document program impact and develop guidelines for land managers that will improve overall program efficiency and further reduce herbicide use in Colorado.

Project Duration: 12 months

Funding Request
Budget Category Funding Requested Matching Non-Federal Funds Matching
Federal Funds
First Year Funding
$46,880
0
0
Second Year Funding
0
0
0
Total Funding
$46,880
0
0

This proposal continues work started in an EPA-funded project.

Executive Summary

In this document we propose to continue a program to evaluate the effectiveness of weed biological control efforts in Colorado. The data generated from this effort will improve the efficacy and efficiency of existing biological control efforts by providing land managers with critical information on site-specific establishment and impact. Further, the data we will generate will provide critical documentation of our program’s effectiveness, information that is critical in maintaining the funding needed for these efforts.

Work completed in 2004 in this effort evaluated the establishment success for weed biological control releases at 239 release locations on four target weeds throughout the state. Further, in 2004 we established 33 long-term monitoring plots where we collected preliminary data and where we propose to continue sampling in 2006. These data will provide us with critically needed information on biological control effectiveness and will allow us to make better recommendations to land managers throughout Colorado and the intermountain west.

The long-term goal of this project is to increase the use of biological control as a weed management strategy in Colorado, thus reducing herbicide use and the associated environmental and human health risks. When effective, biological control eliminates the need for herbicide applications to the targeted weed. Based on results from our 2004 field surveys, we anticipate that many, and perhaps most, of the diffuse knapweed and leafy spurge infestations can be successfully managed with biological control releases. We have less information for the more recently released biological controls for Dalmatian toadflax and field bindweed, but our preliminary data suggests that these arthropods are established and are having an impact on their targets.

Narrative

Non-indigenous species are generating tremendous economic and ecological impacts. In 1992 the Office of Technology Assessment estimated that in the United States, impacts from 79 non-indigenous species resulted in $97 billion of damage from 1906 to 1991. In addition, invasive species significantly impact over 60% of species listed in the Endangered Species Act. Invasive weed species threaten ecosystems by directly competing with and displacing native plants, thus reducing biodiversity and by altering ecosystem processes, such as water cycling and fire regimes. In addition, invaded areas often become less suitable habitat for native animals.

Management of these invaders is difficult. Many of these weeds have invaded large areas of range and parkland in the west, and management of these species through herbicide applications is neither economically practical nor environmentally desirable. Biological control of invasive weeds (the intentional introduction of host-specific herbivores or pathogens of exotic species) has provided dramatic benefits and reductions in several noxious species. However, not all agents that are introduced will control the target species and a species that is successful at some locations may not be successful in all areas.

The State of Colorado is one of the few states that has its own biocontrol agent rearing and distribution program. The state biological control insectary, located in Palisade, CO. has been rearing and releasing biological control agents against weed and insect pests since 1945. The mission of this group is to rear and release approved biocontrol agents of weeds and insects in Colorado. Between 1997 and 1999 insectary personnel made over 1,000 releases of biological control agents against 16 weed species in Colorado.

However, the mandate of the state’s insectary (and thus the budget funds allocated to this group) is devoted to rearing and release of agents. The insectary has few funds and even less time to evaluate the impact of these releases. Evaluation, where there is time, has been limited to determination of whether an organism has established at a specific release site.

In 2003 USDA-APHIS-CPHST established the National Weed Management Laboratory in Fort Collins, CO. One of the missions of this group of scientists is to implement biological control of weeds throughout the Intermountain West. Since 1987, this group (formerly located in Bozeman, Montana) has cooperated in over 150 releases of weed biological control agents in Colorado. Exotic weed targets include leafy spurge, spotted knapweed, diffuse knapweed, Dalmatian toadflax and purple loosestrife. There is a long existing collaboration between the Palisade insectary and APHIS scientists, and now that APHIS has relocated the Bozeman lab to Fort Collins, Colorado has become a major center for biological control research and implementation in the intermountain west. This, coupled with Colorado State University’s strong programs in weed biological control and IPM allows us to attack invasive weed species using multiple research approaches in state, federal and university programs.

This relative lack of evaluation of biological control efforts is not unique to Colorado. Historically, it has proven much easier to fund research and implementation studies focused on finding new agents or distributing them than it has to fund research on biological control impacts. This is in spite of the fact that nearly all biological control researchers recognize that evaluation studies are desperately needed.

Evaluation information serves two important goals:

Documentation of program effectiveness. We need to provide this critical information to private, state, and federal funding sources so that they may make informed decisions about how to spend limited resources in the most effective manner. Documentation of the benefits of weed biological control is critical in maintaining funding for research and implementation.

Further, the permitting process for the introduction of new biological control agents is increasingly focused on a measurement of potential benefits and risks. Documentation of the impact of existing biological control releases is needed so that we may make enlightened decisions about the value of future biological control programs.

Directing and prioritorizing continued biological control efforts. Not all agents that are released are effective at reducing weed populations, and not all effective agents are equally effective in all areas. Information on the causal factors that contribute to agent establishment and impact on weeds at locations throughout the state will allow us to focus our efforts on the most promising agents and locations.

While the research proposed here is limited to Colorado, there are obvious potential benefits to weed management efforts in other states. Both of the goals above are relevant to management efforts in other states, and our data will help these other workers to justify their efforts and to choose the most promising agents. The mission of the National Weed Management Laboratory includes implementing biological control programs in all states. The development of effective evaluation protocols in the project will be valuable in other states and regions as well.

Both the Colorado insectary personnel and the APHIS lab have kept detailed GPS records and site maps of all releases made since 1989, facilitating the project proposed here. This extensive database documents the exact location, target species, agents released and date for each release made.

Accomplishments to Date

In the summer of 2004, we surveyed 239 biological control releases in Colorado and set up permanent monitoring transects at 25 of these sites. An additional 8 monitoring sites were established for weed infestations that have not received releases. The weed species targeted for this effort were spotted and diffuse knapweed, Dalmatian toadflax, leafy spurge and field bindweed, and we surveyed for a total of 13 different biological control agents that have been released.

Work Plan

Long-term monitoring plots

In the summer of 2006, a research team from Colorado State University will continue to collect data on weed abundance, plant community structure and biological control agent populations at the 33 established monitoring sites. These sites were established and baseline data were collected from each in 2004. In addition to the continued monitoring of these sites, we will establish an additional 5 sites per target weed (a total of 20 additional plots) for detailed monitoring. At each of these sites plant community data (e.g. presence and relative abundance of weeds and vegetation types from 100 0.1 m2 quadrats), physical site data (e.g. elevation, exposure, soil type), and biological control agent abundance will be recorded at each site. At each site we will also take a series of digital images to document the site and for use with future comparison images.

Quantifying establishment success.

We will also continue to evaluate the establishment success of biological control releases by visiting additional CDA release sites. In 2004, we visited a total of 239 release sites to check for agent establishment. In 2006, we will visit an additional 150 release sites, concentrating on higher elevation toadflax and leafy spurge sites and in releases made in the southwestern portion of Colorado. These areas were not as intensively sampled as other areas in the 2004 monitoring effort.

With continued data collection at our long-term monitoring plots we will be able to determine if weed densities have declined on release plots compared to weed infestations without releases. As these plots are located throughout the state in a variety of habitats we will be able to refine our recommendations for biological control releases, further increasing the reliability and adoption of this strategy.

Technology transfer

In the fall and winter of 2006 we will present the results from this work at annual meeting of the Colorado Weed Management Association and to the Colorado Weed Network. Both of these groups attract large numbers of federal, state, county, and private weed managers, and both groups have been very receptive to presentations of our first year’s work on this project. This information will be made available to land managers through an extension publication tentatively titled “Establishment Success and Impacts of Weed Biological Control Agents in Colorado.”

Detailed Methodologies

Site Selection

The Colorado Department of Agriculture’s Palisade Insectary has kept a detailed database of releases of biological control agents made in the state of Colorado from 1992 through 2003. The database included releases of 26 arthropod species made on diffuse knapweed (Centaurea diffusa), spotted knapweed (Centaurea stoebe ssp. micranthos), Dalmatian toadflax (Linaria genistifolia ssp. dalmatica), leafy spurge (Euphorbia esula), and field bindweed (Convolvulus arvensis). The database contains information and GPS coordinates for 2235 releases made around the state. From that list, release sites were screened to eliminate those that were obviously located on private lands due to the difficulty in obtaining landowner permission to access those sites for several years. This initial screening resulted in a total of 861 potentially accessible releases on public (city, county, state and federal) lands.

Of those 861 releases, we have checked 226 releases in 23 counties across the state. Release sites were visited based on the phenology of the target weed and life stage of the control agent(s) released at the sites. In 2006 we will survey an additional 150 release sites for biological control agent establishment and density.

Long term monitoring plots

The configurations of the 33 permanent monitoring plots that we have established are site-specific, depending on the shape and extent of the weed infestation present, but always consisted of two 100-meter transects. Ideally transects are set up to create a circular plot, with the transect lines crossing each other at right angles in the center, but with linear infestations we placed the transects parallel to each other. We marked the end points of each transect with sections of 3/8” rebar so that we will be able to sample these same sites in subsequent years. In addition, a digital image was taken of each site to facilitate plot relocation and document the current weed- and non-target vegetation at each site. We will continue to describe the weed and plant community at these sites by using 100 Daubenmire sampling frames (20cm x 50cm, 0.1m2) placed at 2-meter intervals along each transect. Percent cover is estimated for target weed species, shrubs, forbs, grasses, litter, and bare ground. Stem counts are done for individual weed plants rooted inside the frames. If the weed infestation is particularly sparse at any site, stem counts of the target species are also done within a 1-meter band (100m x 2m) on either side of the transect lines. In 2006 we will establish an additional 20 long term monitoring plots and re-sample the existing plots. With these new release sites we will include parts of the state that we were unable to visit in 2004 and we will broaden the habitat types visited for each weed. For example we will visit higher-elevation toadflax and spurge sites as these are of particular interest to land managers. There is little existing information on biological control agent performance under the cooler summers and shorter seasons found at higher elevations.

Biological control agent sampling

Sampling and/or collection of biological control insects will be conducted at the 33 existing long term monitoring sites and at the additional 20 long-term plots that we will set up. The sampling methodology used depends on the life cycles of the biological control agent and its host.

Knapweed species – Root crowns are dug and dissected to determine the presence and abundance of the root-mining beetles Cyphocleonus achates and Sphenoptera jugoslavica. In each monitoring plot one section is selected for such destructive sampling; sampling in subsequent years will be conducted in alternate sections of those plots. For seed-feeding beetles (Larinus minutus, L. obtusus) and fly larvae (Chaetorellia acrolophi, Urophora affinis, U. quadrifasciata), 200 seedheads from the previous year’s flowers are collected and examined for presence of emergence holes (Larinus spp.). Seedheads without emergence holes are caged and examined at weekly intervals for emergent gall flies, and subsequently dissected to assess and count larvae and pupae which do not fully develop or emerge.

Dalmatian toadflax – Two surveys are conducted at each site: visual searches for the presence of the defoliating moth, Calophasia lunula, and the stem-boring weevil, Mecinus janthinus, and tray sampling for the weevils. First, two timed (5 minute) transects are walked in one section of a plot, visually inspecting for the presence of caterpillars or beetles, or foliar damage caused by either agent. The number of stems with agents or damage present or absent is recorded. Subsequent to that survey, 50 stems are randomly selected for closer observations of shoot tips and tray-sampling of beetles which might not initially be visible. Insect sampling is conducted prior to vegetation sampling in order to minimize disturbance of any biological control agents that might be present.

Leafy spurge – For flea beetles (Aphthona spp.) and the stem-boring beetle Oberea erythrocephala we follow the sampling protocol provided by USDA-APHIS, with minor modifications to fit within a monitoring plot. A sweep net is used at 10m intervals along transect lines to sample for any beetles present. A total of 80 sweeps are made, the beetles counted and then released, with the exception of collecting a representative sample of any Aphthona spp. for later identification to species in the laboratory. Insect sampling is conducted prior to vegetation sampling in order to avoid disturbing any biological control agents that might be present.

Field bindweed – At sites where the moth Tyta luctuosa had been released (as well as in control plots) a vacuum sampler is used to collect any moths or larvae that might be present in vegetation or debris under bindweed plants. For the gall mite, Aceria malherbae, we walk three transects for five minutes each, counting the number of bindweed plants with galls present and estimating the percentage of infested plants in the local population.

Data analysis

We will use these data to look for:

  1. patterns of agent establishment. Are there parts of the state where establishment of a given biological control agent has been more or less successful than others? Do environmental factors such as elevation, rainfall, or aspect or target weed density make a difference? For this analysis we will logistic regression to examine habitat variables that are associated with establishment rates.
  2. At which of our long term monitoring sites is there evidence for increases in population size of the biological control agents? Are there any patterns related to the environmental factors mentioned above? This analysis will use a repeated measures analysis of variance to look at population increase through time as a function of the environmental variables.
  3. Are weed populations declining where biological control agents have established? Are there any patterns related to the environmental factors mentioned above? This analysis will also use repeated measures analysis of variance.

Timetable

Major Participants

Local Navigation

Jump to main content.