Technical Service Center
Environmental Applications and Research Group — Publications
Weed Biocontrol Research Program at the Bureau of Reclamation Technical Service Center - Summary of 1996 Activities
Technical Memorandum No. 8220-97-05
Summary of 1996 Activities
Purple Loosestrife Biocontrol Activities
Galerucella: leaf-feeding beetles
Hylobius: root-feeding weevils
Nanophyes: seed-destroying weevils
Outreach and Education
Leafy Spurge Biocontrol Activites
Saltcedar Biocontrol Activities
The Bureau of Reclamation (Reclamation) constructs and manages water storage and delivery systems in the 17 Western states. Frequently, the operation of Reclamation water systems and rights-of-way is impeded by dense growth of either aquatic or terrestrial weeds. The Technical Service Center (TSC) provides assistance with the identification and control of these weeds. In keeping with Department of Interior policy (609 DM 1, June 26, 1995), the use of Integrated Pest Management (IPM) techniques are emphasized. These techniques combine the use of chemical controls (herbicides), mechanical controls (mowing, pulling), environmental controls (cultural methods), and biological controls (insects).
The goals of the weed biocontrol research program are to develop and refine methods of mass- producing selected biocontrol insects for field release, establish and improve methods of monitoring the effects of these insects on both target and non-target plants, and provide guidance for the proper revegetation of the site. Existing methods of accomplishing these target goals usually need to be adapted for use at Reclamation facilities due to water-management needs and the physical environment of the sites and structures.
Purple loosestrife (Lythrum salicaria) is a perennial, non-native plant with attractive purple flower spikes. It out competes native species and forms dense monocultures in wetlands due in part to its high reproductive capability (one mature plant can produce two million seeds a year) and the absence of effective native predators. This invasive plant is a serious problem in some Reclamation systems, a newcomer to others, and still unidentified in a few. In areas where it is found, it rapidly impedes Reclamation water systems and degrades associated wetland habitats.
Three groups of insects are being used for biocontrol of loosestrife: leaf-feeders, root-feeders, and flower-feeders. Initial Reclamation field research on biological control of purple loosestrife began at three Denver-area sites in 1994: Coot Lake in Boulder, the Federal Correctional Institute (FCI) in Englewood, and Ward Lake Tree Farm in Lakewood. In 1995, work began at a site south of Ephrata, Washington. This site is on Reclamation property at the Columbia Basin Project, Winchester Wasteway and is surrounded by 25,000 acres (1989 aerial survey) of a near- monoculture of purple loosestrife. Details on 1994 and 1995 activities can be found in Bureau of Reclamation Technical Memoranda Numbers 8220-95-1 and 8220-96-13.
The establishment of a biocontrol insect species can be affected by many factors, probably the most significant of which is the weather. The winter of 1995-1996 in the Denver area was colder than 1994, with lows reaching -15 F, and little snow cover at the time (see Appendix II). Precipitation and temperatures during breeding season were normal, unlike 1995 when the spring and summer were unusually cold and wet. Winter conditions at Ephrata were more extreme than normal, with colder temperatures and more days with snowcover.
Conditions available to the insects for overwintering in the Denver area may have caused varying survival rates at the three sites. Counts of Galerucella beetles in May 1996 suggested that the overwintering success at FCI was less than at Coot Lake or Ward Lake. Management practice at the FCI site had been to mow close to the edge of the water. This may have left the beetles with only minimal plant litter on dry land to provide cover for overwintering. Combined with cold temperatures and lack of snow cover, this may have caused high mortality. Management practices were altered to leave an unmowed border of a few feet for the last several mowings of 1996.
The first site visits of the year were made on May 6, 1996. Emerging perennial loosestrife plants at Coot Lake were 2-6 inches tall, 2-8 inches at Ward Lake, and 1-3 inches tall at FCI. About 60% of the plants at Coot Lake had blackened apices from freeze damage, Ward had about 10% damage, FCI had none. Galerucella calmariensis and Galerucella pusilla beetles were seen at both Coot and Ward Lakes. Judging from the amount of feeding, they had only come out within the previous day or two. No insects or feeding were observed at FCI until May 13. By that time, insects and signs of feeding at the other two sites had increased markedly and eggs were found on plants at those sites. The emergence of the insects at Ward Lake was correlated with the lilacs blooming and the leaf buds of Marshall Seedless Ash and cottonwoods beginning to open.
Galerucella beetles to be used for mass production at Reclamation's Technical Service Center in 1996 were overwintered in plastic ziplock bags or screen cages at 43 F in a growth chamber. This was not very successful; from an original 690 insects only 73 survived. This number was supplemented with 180 insects supplied by Dr. Bernd Blossey of Cornell University, and eight insects collected from the Coot Lake site to give 261 beetles used for mass production. Insects were placed on sleeved greenhouse plants on May 1, 1996 and these plants were moved out into the greenhouse ponds on May 15. Tenerial (newly-hatched) beetles began emerging on June 21, fifty-one days after adults were placed onto plants. A total of about 6,300 adult beetles were harvested. Three thousand two hundred of these beetles were taken to Ephrata, WA for release and the rest were retained as breeding stock for the 1997 season. This stock was overwintered on potted plants in the growth chambers at 40 F.
Methods of mass producing the insects were streamlined from 1995 as a result of Dr. Blossey's suggestions. Insect rearing was conducted on sleeved plants in a pond behind the greenhouse. Construction of a framework to support the plants was led by Matt Antony of Boy Scout Troop 814 as an Eagle Scout project (photos 1,2,3 ). Use of this facility and new methods greatly reduced the staff time needed to produce large quantities of beetles.
In November 1996, inmates at FCI dug a supply of loosestrife roots for use in mass rearing in 1997. These roots were taken to the Federal Center and stored outside under a thick layer of straw and permeable landscape fabric. They will be washed and potted in early spring 1997.
The Hylobius transversovittatus adults that overwintered in the growth chambers suffered no mortality over the winter. The addition of 42 newly-emerged adults throughout 1996 brought the current total of adults to 109. No adults were released into the field in 1996.
Total egg production for the 1996 season was 938 eggs. Of these, 314 eggs were placed onto greenhouse plants, 424 onto plants at Coot Lake, 107 on plants at FCI, and 93 eggs went to Ward Lake. Eggs were inoculated by two methods - either in the soil next to small roots, or vertically into a stem cut off at 4 inches high. The stem inoculations were marked with surveyor's tape and success was evaluated at the end of the season by dissecting the stem. In the greenhouse, about 98% of the stems inoculated showed feeding and tunneling down into the root. In the field, the success rate of stem inoculations was lower, although not all the stems could be re-located for evaluation. At Coot Lake, 21% of the stems showed tunnels leading into the root; in 1995 the rate was 25%. FCI had a 68% success rate, and Ward Lake showed a 64% success rate for stem inoculations. The reason for the lower rate of success at Coot Lake is not yet clear, so we will continue to collect data on local microclimates and the presence of potential predators. Although some eggs inoculated in previous years may have emerged as adults this year, no signs of adults were noted at any field sites.
Joint research with Cornell University was inititated on the development of an artificial diet for rearing Hylobius. Funding was provided to Cornell to conduct initial trials of the diet, and it was found that insects could mature from egg to adult in only 9-10 weeks when a specific recipe was used. It normally takes one to two years for Hylobius to mature from egg to adult under field and laboratory conditions when using normal root material and conditions. The feasibility of releasing adults into field sites will be greatly enhanced by using the artificial diet and incubating the eggs in a controlled-environment growth chamber. Currently, only eggs are placed at field sites and methods of obtaining and inoculating these eggs are very time consuming.
Loosestrife roots were dug early in May at FCI for use in the artificial diet being developed for Hylobius larvae. These roots were washed and chopped into 1-inch pieces before being frozen. Then they were placed into a blender with dry ice and processed until the material would pass through a 1.7mm sieve. This material was frozen again for later use this winter in testing the artificial diet.
Dr. Blossey again attempted to collect parasite-free Nanophyes brevis at field sites in Europe, but insects at all the sites visited were parasitized. The future possibilities for the introduction of this species into North America is uncertain.
Three hundred Nanophyes marmoratus were placed into plastic bags and overwintered in the dark at 43 F in a growth chamber . However, only 21 insects survived until May 1996. These were placed onto two sleeved greenhouse plants that were eventually moved outside into the greenhouse pond. These two plants produced several hundred Nanophyes. Most of these insects were released in August at the same FCI site where Nanophyes were released in 1995, but 77 were collected for overwintering in the growth chambers.
Some Nanophyes released at the FCI field site in 1995 survived over winter, and adults were spotted at the release site several times. The first sighting was on May 13, when it was also noted that Galerucella adults had just emerged.
At the beginning of the previous (1995) growing season, no national standards for monitoring the effectiveness of biological control for purple loosestrife had been established. This was a matter of concern, as researchers wish to draw together all the North American data into one of the first well-documented studies on biological control of an exotic plant species.
Preliminary monitoring criteria for the national standards have now been tested throughout the 1996 season, and will undergo only slight additional modification. Monitoring is done at permanent 1 m2 quadrats three times per season, timed to give the best data for insect abundance and impact on the plants. Selected monitoring data for all sites is in Appendix III. This data will be used as baseline data for yearly comparisons. The most striking results were seen in one quadrat at Ward Lake; there was very heavy feeding and noticeable damage to plant growing points and flowers (photos 4,5,6). This type of damage should become more widespread as Galerucella populations increase over in the next few years.
Aerial photographs were taken at all three Denver-area sites, and at the Ephrata site and surrounding infestation. Additional reference ground photos were taken of each quadrat and of the general area at the Denver-area sites.
Purple loosestrife display
A photographic display (photo 7) was constructed to inform the public about problems caused by purple loosestrife and how they can help to control loosestrife. It encourages them not to plant ornamental loosestrife and to distinguish the plant from desirable "lookalikes." This display, complete with freestanding 8 foot x 10 foot display board, is available for public display and can be scheduled by calling Bonnie Gehringer at (303) 236-3729 ext. 223.
Copies of a videotape titled Restoring the Balance: Biological Control of Purple Loosestrife were purchased from Cornell University. These tapes were provided to site cooperators by our purple loosestrife biocontrol program, and a copy can be borrowed by calling Debra Eberts at (303) 236-6007 ext 245. This is a 28 minute tape that discusses the problems loosestrife can cause, various management alternatives and their effectiveness, techniques for mass-rearing of biocontrol insects, and risks associated with releasing imported insects.
Site cooperators were given a museum mount (photo 8) of all adult insects currently used for loosestrife biocontrol. These boxes also illustrate examples of adult and juvenile feeding for each insect, and can be used by cooperators to verify insect identification and feeding at their sites.
Ephrata site visit
Dr. Bernd Blossey of Cornell University visited the Reclamation field site for loosestrife control near Ephrata, WA in July 1996. During this visit, potential future biocontrol projects for other weeds (Eurasian watermilfoil, knapweed, leafy spurge, thistle) were discussed for several specific sites.
Dr. Blossey's recommendations for continuation of loosestrife biocontrol at Ephrata include:
- Coordinate continued herbicide spraying programs for loosestrife so that the beetle populations are not negatively affected (establish buffer zones).
- Focus insect stocking programs on small populations of loosestrife in local depressions, since these populations are often still mixed communities with presence of other wetland species. The success in suppression of loosestrife will be easier to assess and faster in small populations.
- Avoid insect releases close to active agricultural fields since pesticide drift might negatively affect the biocontrol insects.
- Avoid release if reed canarygrass or Phragmites have established populations in the target area. It is likely that they would expand as loosestrife decreased.
- Monitoring of the effect of control agents on the extent of loosestrife infestations should occur according to the developed monitoring guidelines at as many sites as possible.
Mass-rearing techniques will be changed slightly to make them more efficient. We will continue to use the pond and support structure, but will use several large enclosures covering a number of plants rather than individual plant sleeves. Most Galerucella produced will be released at the newest site in Washington, but insect populations at the Denver sites (especially FCI) may be supplemented if production is as high as hoped.
We will continue to work with Cornell University on development of an artificial diet. Using the environmental growth chambers at the Denver Federal Center, we will try to identify the best set of conditions for raising Hylobius on this diet. Various temperature regimes will be tested to find the combination giving the highest and quickest production of fertile adults. We will also try various techniques to reduce the incidence of molds and mites infesting the media and causing reduced survival in trials at Cornell University.
Inoculation of eggs at field sites may be decreased in favor of rearing adults on the artificial diet and then releasing the adults at field sites. Eggs placed into the field sites in previous seasons may emerge as adults, so sites will be monitored closely for evidence of adults. Hylobius adults are reclusive and are active at night and on cloudy days. They are very difficult to find, so evaluations of their presence will rely mostly on observations of the plants for evidence of feeding and ovipositing damage.
This insect seems more suited to field production than laboratory rearing. A small number will again be produced on sleeved plants at the greenhouse pond next year, but we will rely on field populations to supply insects for new sites. The population at FCI will be monitored closely to see how rapidly it increases and spreads.
We will not plan to release Nanophyes in other areas before 1998. This is both because of the currently limited population available for stocking, and the need to avoid seed production at our cooperators' sites. Seed production has been controlled in the past by cutting the flower spikes, which is not compatible with the life cycle of the insect (they lay eggs into the flowers). We plan to wait until naturally increasing field populations of Galerucella cause declines in the numbers of flowers and seeds produced. By that time, the population of Nanophyes at FCI will likely have increased to the point where some insects can be collected and taken to other sites. This will eliminate the need to cut flower spikes without the danger of producing a stock of seed that can move downstream to infest other sites.
Ground surveys will be continued at all Denver-area sites. Data will be gathered at three times during the growing season to determine the status of insects and plants and compare with 1996 data. Data collection in Ephrata, WA will coincide with the last two visits to Denver-area sites. These monitoring criteria have been tested by several cooperators, and will be reviewed at a meeting early in 1997.
Good aerial photos were obtained for all sites at peak-flowering time in 1996. Analysis and ground-truthing of these photos using GPS (Global Positioning System) and GIS (Geographic Information System) will continue in 1997. It may not be necessary to have more aerial photos taken in 1997, as changes due to biocontrol would not be dramatic in one year's time.
Leafy Spurge (Euphorbia esula) is an aggressive perennial that grows to a height of 3 feet and produces a milky latex that is irritating to cattle and humans. The deep root system of this non- native plant makes it very difficult to control by mechanical or chemical methods. While leafy spurge is primarily a rangeland weed, it occurs on Reclamation ditchbanks and rights-of-way. Weed control activities in these areas are heavily influenced by the proximity to water. The resulting maintenance problems from the structural effects of the roots on the banks, irritation from the sap, and the need to avoid infesting neighboring agricultural fields and rangeland require action from Reclamation managers.
A number of insects have been introduced into the United States for the biological control of leafy spurge, each with its own environmental preferences. In a local effort to gain experience in matching species to site conditions and also in monitoring the results, Reclamation began a cooperative project with Jefferson County Weed and Pest Control (JeffCo). In June of 1995, JeffCo purchased and released several biocontrol species at a private site near Pine, CO. Reclamation supplied two 12-foot screen tents for the releases (photos 9, 10), and will be conducting future monitoring of the site. The insects released were Spurgia esulae, Apthona nigriscutus, and Oberea erythrocephala.
Reclamation has taken aerial photos of the release site for future reference and assessment of the effectiveness of control methods. We also conducted preliminary plant height and density measurements in late July 1996 (Appendix III). At that time, we sampled for insects at the release sites using sweep nets, but did not retrieve any (photos 11, 12). JeffCo personnel reported seeing evidence of S. esulae earlier in the month, and we photographed areas we believe show plant response to insect feeding (photo 13). We plan to continue monitoring this site in 1997, and to begin work on leafy spurge infestations on Reclamation facilities in North Dakota.
Saltcedar (Tamarix sp., especially ramosissima) is a non-native shrubby tree that has become a noxious weed in western riparian systems. Native vegetation such as cottonwoods and willows are replaced by dense monocultures of saltcedar. This tree depletes groundwater resources, and increases soil salinity, soil erosion and flooding events. Where this plant has invaded Reclamation systems, it creates an expensive management challenge to effectively manage water and habitat resources.
Chemical and mechanical methods have been successful in managing saltcedar at some sites, but these methods are expensive and labor-intensive. Dr. C. Jack DeLoach of the U.S. Department of Agriculture, Agricultural Research Service has been researching possible biocontrol insects for saltcedar at the Grassland, Soil, and Water Research Lab in Temple, Texas. He has met with Reclamation to evaluate possible release sites on Reclamation property near Pueblo, Colorado (photo 14). However, any releases have been put on hold until an Environmental Assessment (EA) can be prepared and returned with a finding of no significant impact (FONSI). This became necessary when the southwestern subspecies of the willow flycatcher, which spends part of its time in saltcedar, was designated as an endangered species.
Reclamation facilities at the Denver Federal Center are not equipped to be an insect quarantine facility. For that reason, we will not work with any of the potential biocontrols in these facilities until a FONSI is granted. In the interim, we will visit the laboratory in Temple to observe methods of rearing the insects and to prepare our facilities accordingly. We will also continue our efforts to develop a pest-free stock of saltcedar in our greenhouse for future use in rearing biocontrol insects. Aerial photographs of the potential release sites were taken in 1996 to estimate baseline (pretreatment) infestations.
We would like to express our appreciation for the contributions and support from the following:
- Partnership Resources
- Bureau of Reclamation Research Program WATER Project EE007, "Development of Improved Aquatic Site Pest Management Methods"
- Bureau of Reclamation Program Analysis Office
- Bureau of Reclamation, Pacific Northwest Region
- Dr. Bernd Blossey, Cornell University
- Dr. C. Jack DeLoach, USDA-ARS
- City of Boulder, Colorado, Division of Mountain Parks
- U.S. Dept. Of Justice, Federal Correctional Institution, Englewood, Colorado
- Ward Lake Tree Company
- Jefferson County, Colorado, Weed and Pest Management Division
- Bureau of Reclamation, Pacific Northwest Region
- Bureau of Reclamation, Ephrata Field Office
- Bureau of Reclamation, Eastern Colorado Area Office, Loveland
- Bureau of Reclamation, Pueblo Field Office
- City of Boulder, Colorado, Open Space Program
- Colorado Division of Wildlife
- Colorado Department of Agriculture