Biological Control of Spotted Knapweed and Canada Thistle at The Fort Carson Military Reservation, Ft. Carson, Colorado 1997 Progress Report Submitted to the Directorate of Environmental Compliance and Management, Ft. Carson, Colorado Original photo by R.D. Richard G. J. Michels, Jr., D. A. Fritts, and J. B. Bible The Texas Agricultural Experiment Station P.O. Box 10, Bushland, TX 79012 BIOLOGICAL CONTROL OF SPOTTED KNAPWEED AND CANADA THISTLE AT THE FORT CARSON MILITARY RESERVATION, FT. CARSON, COLORADO 1997 PROGRESS REPORT by G. J. Michels, Jr., D. A. Fritts, and J. B. Bible submitted to the United States Army, Directorate of Environmental Compliance and Management, Ft. Carson, Colorado Introduction The goal of the biological control of weeds program is to reduce the existing populations and control the spread of selected state- and federal-listed noxious weeds at two military installations located on the Front Range of the Rocky Mountains in Eastern Colorado. The two sites are, the Fort Carson Military Reservation (FCMR) at Colorado Springs, CO and the Pinon Canyon Maneuver Site (PCMS) at Trinidad, CO. In the initial program, spotted knapweed, Centaurea maculosa Lam., and Canada thistle, Cirsium arvense (L.) Scop., will be the target species. The objectives of the research are to 1. Develop and implement procedures and sampling methods to assess the present state of any existing biological controls on the selected species at FCMR and/or PCMS; 2. Monitor abiotic and biotic factors which may be peculiar to FCMR and/or the PCMS through field data collection and release-site weather stations. Assess the impact of these factors on establishment of natural enemies; 3. Conduct greenhouse studies to determine the interaction of several available natural enemies of the selected weed species with each other and their combined effect on the plant, and conduct herbicide/natural enemy compatibility tests to help make decisions for IPM strategies. Use the greenhouse populations of the natural enemies for additional releases; 4. Release several species of natural enemies in field trials using release cages and open field releases to compare survival and establishment over a period of at least three years. Monitor and redistribute established populations. Knapweed is an aggressive annual weed, has little nutritive value and is an invasive competitor, decreasing forage production as much as 60 to 90 percent. Spotted knapweed is one of the most important rangeland weeds in western North America with approximately 287 million ha infested. Canada thistle is an aggressive dioecious perennial, which grows in patches and has a diverse habitat. Because of its random distribution, it is difficult to determine complete losses, but is considered to be a noxious weed in at least 34 states in the United States. This report describes the progress during 1997 and early 1998. Several organizations have cooperated with this project, including the Colorado Department of Agriculture, Pennsylvania Department of Agriculture, Forestry Sciences Laboratory at Montana State University and USDA-APHIS at Montana State University. Chronology April In cooperation with Mrs. Robin Romero, United States Fish and Wildlife Service at Fort Carson, Mr. James Kulbeth, Directorate of Environmental Compliance and Management, and Mr. Fred Stahl, Colorado Department of Agriculture, release sites were located. One spotted knapweed site was located near Turkey Creek. Two Canada thistle sites were located, and designated as ARA and Reservoir. The surrounding areas were surveyed for vegetation species. Spotted knapweed seed heads were collected to determine if insects were currently present. The knapweed seedhead fly, Urophora quadrifasciata (Meigen), was found in the collection. Two cages, fabricated of Lumite® screen mesh over 4’ x 6’ x 6’ high steel square tubing frames, were erected at each site except Turkey Creek. The netting for one cage needed repair and was placed at a future date. A weather station was placed at the ARA site. May A second spotted knapweed site was located in the Cantonment area, designated as Cantonment I, and two cages were erected. The netting was placed on the second cage at the Turkey creek site. Project signs reading, “Biological Control of Noxious Weeds, Please Do Not Disturb, A Cooperative Research Program: DECAM, The Texas Agricultural Experiment Station, The Colorado Department of Agriculture,” were placed at Turkey Creek, Cantonment I, ARA, and Reservoir (Fig. 1). June Adult lesser knapweed flower weevils, Larinus minutus Gyll., were field collected at two sites near E. Helena, MT, with the assistance of Mr. Ronald Lang, USDA-APHIS on June 2, 1997. At the first site approximately 3400 insects were collected. Most of these insects were collected from about 17 diffuse knapweed plants (Fig. 2). Mr. Lang stated releases were made at this site in 1993 and this could be the last year for collections since L. minutus had eliminated the diffuse knapweed infestation. Weevil numbers were much lower at the second site. The weevils were sorted and place into individual containers. On June 3, 1997 nine spotted knapweed bouquets containing the banded gallfly, Urophora affinis Frauenfeld, were collected near the Jefferson River. This site was approximately 5 miles west of Three Forks, MT, and 65 to 70 miles southeast of E. Helena, MT. Each bouquet contained approximately 1200 larvae. Field releases were made on June 5, 1997 at the Turkey Creek and Cantonment I sites. At each site, 30 to 50 L. minutus were released into one established cage and 50 to 70 released on uncaged plants. A total of 100 insects were released at each site (Table 1). A flag was placed at each open field point of release. Figure 1. Outdoor cage and project sign at Cantonment I release site. Summer, 1997. Figure 2. Larinus minutus feeding on diffuse knapweed at East Helena, MT. June 1997. Table 1. Summary of Insects Released for Biological Control of Canada Thistle and Spotted Knapweed at Ft. Carson, CO, 1997-1998. Common name Species Source Agency Release Notes Date Site1 Number Total Caged Open Canada thistle (Cirsium arvense ) Thistle-feeding shield beetle Cassida rubiginosa Harrisburg, PA Penn. Dept. of Agric. 07/03/1997 4 25 0 25 Canada thistle bud weevil Larinus planus Harrisburg, PA Penn. Dept. of Agric. 07/03/1997 3 47 0 47 Thistle stem gall fly Urophora cardui LaGrande, OR Forestry Sci Lab 01/28/1998 6 0 77 539 3 Thistle stem gall fly Urophora cardui LaGrande, OR Forestry Sci Lab 01/28/1998 7 0 92 644 3 Spotted knapweed (Centaurea maculosa ) Knapweed peacock fly Chaetorellia acrolophi Palisade, CO Colo. Dept. of Agric. 07/02/1998 2 250 250 500 Knapweed root weevil Cyphocleonus achaetes Palisade, CO Colo. Dept. of Agric. 08/06/1997 5 50 200 250 Lesser knapweed flower weevil Larinus minutus Helena, MT USDA/APHIS 06/05/1997 1 30-50 50-70 100 4 Lesser knapweed flower weevil Larinus minutus Helena, MT USDA/APHIS 06/05/1997 2 30-50 50-70 100 4 Spotted knapweed seed head moth Metzneria paucipunctella Spokane, OR USDA/APHIS 04/28/1998 6 2 0 3456 5 Spotted knapweed seed head moth Metzneria paucipunctella Spokane, OR USDA/APHIS 04/28/1998 7 2 0 3456 5 Spotted knapweed seed head moth Metzneria paucipunctella Spokane, OR USDA/APHIS 04/28/1998 1 0 1728 5,6 Banded gall fly Urophora affinis Three Forks, MT USDA/APHIS 06/05/1997 1 1 3 4800 2,4 Banded gall fly Urophora affinis Three Forks, MT USDA/APHIS 06/05/1997 2 1 3 4800 2,4 Knapweed seed head fly Urophora quadrifasciata determined to be previously established at Turkey Creek site 1 Sites: 1 - Cantonment I; 2 - Turkey Creek; 3 - ARA; 4 - Resevoir; 5 - Cantonment II, 6 - Outdoor Recreation, 7 - Duck Pond. 2 Released in bouquets of dead spotted knapweed with approximately 1200 larvae/bouquet. 3 Released in galls, approximately 7 larvae/gall. Releases were made in small screened boxes to prevent rodent predation. 4 Recovered on 7/2/98. 5 Released in screened boxes containing infested seedheads; 2,400 seedheads/box, approx. 1728 larvae per box (72% infestation). 6 Released at HazMaterials Site which was accidentally mowed at a later date, then abandoned. Two cages were established at Turkey Creek and Cantonment I sites so that complimentary insect releases could be made. Bundles of spotted knapweed plants containing an estimated 3600 open and 1200 caged U. affinis larvae were introduced (Table 1, Fig. 3). July Larinus planus (F.), the Canada thistle bud weevil, and a thistle-feeding shield beetle, Cassida rubiginosa Müller, were field collected on July 2, 1997 by Mr. Jim Stimmel, Pennsylvania Department of Agriculture, Harrisburg, PA, for release on Canada thistle. One half of the collection was shipped to Fred Stahl, Colorado Department of Agriculture, Palisade, CO, while the other half was shipped to Fort Carson Military Reservation for the purpose of monitoring establishment and population increases. On July 3, 1997 25 adult C. rubiginosa were released into one cage at the Reservoir site and approximately 47 adult L. planus were released into one cage at the ARA site (Table 1). Due to low collection numbers, no open releases were made at either site. August On August 6, 1997 a second spotted knapweed release site was located in the Cantonment and designated as Cantonment II. One caged and four open field releases of adult knapweed root weevils, Cyphocleonus achaetes (Fahr.), were made (Table 1). Fifty beetles were released at each site. The beetles were provided by Fred Stahl, Colorado Department of Agriculture, Palisade, CO. On August 27, 1997 plant height and density were recorded at Cantonment I, Cantonment II, Reservoir, and ARA sites (Tables 2 and 3, Figs. 4, 5, 6 and 7). Cage screens were removed from frames at release sites except for Cantonment II containing C.