Sulfur cinquefoil (Potentilla recta) is long-lived perennial weed that is a prolific seed producer and is adapted to nearly every soil type and vegetation complex in the western U.S. This invader reproduces solely by seed. This two-year study found that defoliating sulfur cinquefoil during flower or later phenological stages reduced the plant’s yield and seed production. The viability of seed consumed by livestock was reduced, and all viable seed was passed within three days of consumption. Livestock grazing and mowing appear to be management options worth investigating for suppressing sulfur cinquefoil.
This project addressed four specific objectives. Objectives 1-3 are separate research questions, each of which is capable of producing conclusive results independent of the others. The purpose of Objective 4 is to synthesize and distribute the information gained from each of the previous objectives.
The objectives are:
1) Determine the effects of different timings, frequencies and intensities of sulfur cinquefoil defoliation on a) plant yield, b) plant vigor, and c) seed production and viability.
2) Examine sulfur cinquefoil seeds passing through the digestive tract of sheep and goats for a) time required to complete passage, and b) viability of seeds after passage.
3) Evaluate the tannin content of sulfur cinquefoil a) at different phenological stages (pre-flower, flower and post-flower), and b) in response to clipping.
4) Synthesize and disseminate the findings of the above projects to livestock producers, county extension agents and other educators, resource agency personnel and others to facilitate the development of grazing plans that reduce the spread of sulfur cinquefoil.
Previous research and observations indicate that sheep and goats will consume sulfur cinquefoil, therefore, Objectives 1-3 are exclusively designed to address:
1) the biological response of the plant to defoliation,
2) the propensity for sheep or goats to spread viable seed, and
3) the chemical composition of the plant at different seasons.
Sulfur cinquefoil (Potentilla recta L.) is an exotic perennial forb that can flourish in a variety of soil types and climates (Rice 1999). It is currently classified as “noxious” in five western states (USDA 2011). The plant is a concern on rangelands because of its ability to invade healthy, undisturbed native plant communities and replace native species (Rice 1999; Lesica and Martin 2003; Naylor et al. 2005). The plant reproduces only by seed, but each plant can produce thousands of seeds per year (Dwire et al. 2006), and individual plants can live as long as 20 years (Perkins et al. 2006). This massive production of seed enables sulfur cinquefoil to quickly dominate disturbed areas such as roadsides, clear cuts and abandoned fields and to form monocultures on vast expanses of rangeland (Figure 1).
Control options for suppressing sulfur cinquefoil yield and seed production are few. Sulfur cinquefoil is closely related to domestic strawberries and native cinquefoil plants, making it a poor candidate for biological control (Duncan et al. 2004). Prescribed fire is ineffective (Lesica and Martin 2003), and herbicides have provided mixed results (Powell 1996, Rice 1999, Lesica and Martin 2003, Duncan et al. 2004, Sheley and Denny 2006, Endress et al. 2008). Re-treatment is often necessary after three-five years (Lesica and Martin 2003, Duncan et al. 2004), which is usually cost-prohibitive for farm and ranch businesses or other landowners (Lesica and Martin 2003).
It has been recommended that management of sulfur cinquefoil infestations should focus on controlling seed production and preventing the introduction of seed into uninfested areas (Dwire et al. 2006, Perkins et al. 2006). Research by Kiemnec and McInnis (2009) indicated that two-three years of controlling sulfur cinquefoil seed production would not eliminate seeds in the soil but would severely deplete the existing seedbank. Repeated defoliation can greatly reduce the accumulated soil seedbank of other perennial noxious weeds, such as leafy spurge (Euphorbia esula L.) and spotted knapweed (Centaurea stoebe L.). Bowes and Thomas (1978), demonstrated that eight years of repeated sheep grazing reduced the soil seed bank of leafy spurge by over 99% compared to ungrazed areas. Similarly, the number of viable spotted knapweed seeds in the seedbank was reduced by 54% after three summers of sheep grazing in southwestern Montana, while seed numbers in ungrazed areas increased by 88% (Olson et al. 1997). Mowing has been used to effectively suppress other invasive perennial forbs such as spotted knapweed (Watson and Renney 1974, Rinella et al. 2001) and Canada thistle (Cirsium arvense) (Schreiber 1967). Mowing spotted knapweed during the flowering stage, or bud and flowering stage, reduced seed germination from 91% to 19% and reduced the number of seed-producing plants by 91% (Watson and Renney 1974). Even so, mowing is a relatively expensive control option (Brown et al. 1999) that is limited in application to suitable topography. Furthermore, Rice (1999) cautions that mowing may cause sulfur cinquefoil plants to develop heavier rootstocks and alter their growth form, keeping more of their aboveground growth near ground level.
Targeted grazing (a.k.a., prescribed grazing) by sheep and goats is being used to control some invasive weeds, however, there is little information on how sulfur cinquefoil responds to defoliation. It is known that sheep (B.E. Olson, unpublished data), goats (R.A. Frost, personal observation) and cattle (Parks et al. 2008) will graze sulfur cinquefoil plants. It is unknown whether livestock grazing will decrease viable seed production or yield of sulfur cinquefoil. Before targeted grazing experiments are initiated with cattle, sheep or goats, a controlled study to evaluate different timings, frequencies and intensities of defoliation is necessary to determine if grazing can control the plant and to create a valid grazing prescription.
A major concern when using targeted grazing to suppress invasive weeds is that if livestock consume viable seed, the animals may disseminate it in other areas, thereby contributing to weed expansion (Bartuszevige and Endress 2008). Elk, deer and cattle have all been observed eating the seedheads of sulfur cinquefoil in the fall (Parks et al. 2008), and sheep and goats will graze both the foliage and the seedheads (R. Frost, personal observation and B. Olson personal communication). Viable seeds of sulfur cinquefoil have been recovered from the pellets of deer (Bartuszevige and Endress 2008), however, it is unknown if livestock consuming the seeds of sulfur cinquefoil can further spread the plant through endozoocory. Livestock and wildlife are capable of passing viable seeds of other noxious weeds, including leafy spurge (Lacey et al. 1992, Olson et al. 1997, Wald et al. 2005), spotted knapweed (Wallander et al. 1995), jointed goatgrass (Triticum aestivum L.; Lyon et al. 1992), thistle spp. (Holst and Allan, 1996) and perennial pepperweed (Lepidium latifolium L.; Carpinelli et al. 2005). Consequently, Hogan and Phillips (2011) contend that weed seed transmission by livestock is an ecological concern that should be addressed at the local, national and global levels.
To prevent the spread of noxious weeds, dry-lotting animals is recommended as a best management practice before moving animals to areas not infested with noxious weeds (Kott et al. 2006). It is important to know the length of time animals should be dry-lotted to prevent the passage of viable seed to decrease the amount of time, labor and feedstuffs required to drylot animals before returning them to rangeland grazing. Furthermore, sulfur cinquefoil flowers incrementally, so any prolonged grazing during the flower stage could result in sheep consuming seed at the soft dough, hard dough and mature stages. It is prudent to test these different stages for viability post-consumption (Olson and Wallander, 2002).
This two-year field study was located on private land owned by Rose Creek Ranch on foothill rangeland near Bozeman, MT. One hundred fifty sulfur cinquefoil plants between 10 and 33 cm in height were selected each year (2006, 2007) on a site moderately infested with sulfur cinquefoil. The 150 plants were fenced in an area approximately 430 m2 with 1.8-m tall welded wire panels to exclude ungulate grazing. The 2007 exclosure was located about 25 meters from the 2006 exclosure to ensure that results from the two years were independent. Study plants were tagged for identification and located a minimum of one meter apart. The percent canopy cover of sulfur cinquefoil, other forbs and perennial graminoids was estimated inside a 1-meter diameter (0.79 m2) hoop surrounding each plant to account for potential competition from neighboring vegetation, and the initial height of each treatment plant was measured to the nearest centimeter. Fifteen hand-clipped treatments were applied to the individual sulfur cinquefoil plants, with ten plants included in each of the fifteen treatments (n = 150 plants per year). The use of hand clippers to simulate grazing allows for strict control of the timing and intensity of defoliation that cannot be achieved with grazing animals. Also, many more combinations of timings and intensities of defoliation can be evaluated using this clipping approach than could be evaluated in one grazing trial.
Treatments included: 1) clip plants to 7-cm stubble height (35-90% relative utilization, mean = 59%) during pre-flower (bolting) stage (mid-June); 2) clip plants to 15-cm stubble height (1-63% relative utilization, mean = 27%) during pre-flower stage (mid-June); 3) clip plants to 7-cm stubble height (55-91% relative utilization, mean = 81%) during flowering stage (late-June); 4) clip plants to 15-cm stubble height (25-76% relative utilization, mean = 62%) during flowering stage (late-June); 5) clip plants to 7-cm stubble height (65-94% relative utilization, mean = 85%) during seed ripe stage (early-July); 6) clip plants to 15-cm stubble height (50-84% relative utilization, mean = 72%) during seed ripe stage (early-July); 7) Treatment 1+Treatment 3 (7 cm, pre-flower + flower); 8) Treatment 1+Treatment 5 (7 cm, pre-flower + seed ripe); 9) Treatment 3+Treatment 5 (7 cm, flower + seed ripe); 10) Treatment 1+Treatment 3 +Treatment 5 (7 cm, pre-flower + flower + seed ripe); 11) Treatment 2+Treatment 4 (15 cm, pre-flower + flower); 12) Treatment 2+Treatment 6 (7 cm, pre-flower + seed ripe); 13) Treatment 4+Treatment 6 (15 cm, flower + seed ripe); 14) Treatment 2+Treatment 4+Treatment 6 (15 cm, pre-flower + flower + seed ripe); and 15) unclipped control.
The total aboveground biomass of each plant was collected at the time of seed collection. Individual plants were hand-clipped to ground level and dried for 24 hours at 100 C. The seedheads of plants were collected first, bagged separately and dried for 48 hours at 40 C to prevent the drying process from negatively impacting the subsequent viability testing of the seeds (Wallander et al. 1995). Dry weights of the plants and corresponding seedheads were combined to calculate total biomass production for each treatment plant.
Number of Buds/Flowerheads. For each treatment, the number of buds and flowerheads per plant was counted prior to being collected. Immature buds, distinguished from newly forming leaves by visible bracts, were included in the final count.
Number of Seeds. The number of immature, intermediate and mature seeds per plant and total number of seeds per plant were counted in the laboratory. Seeds were extracted from seedheads using a rub board. Seeds from each plant were then divided into three developmental stages: 1) immature [tiny, seedcoat light brown]; 2) intermediate [medium-sized, seedcoat dark brown, netting not visible to the naked eye]; and 3) mature [large, seedcoat nearly black with visible cream-colored netting] and were counted by stage. Total number of seeds per plant was calculated by totaling the number of seeds in each of the three developmental stages.
Percent Viability of Seeds. Seeds were tested for viability using the tetrazolium (TZ) test (Grabe 1970). Three subsamples from each of the immature, intermediate and mature developmental stages of seeds from each treatment plant were used. Seeds within a given developmental stage were randomly assigned to one of three subsamples. Each subsample contained either 20 seeds or one-third of the total number of seeds in that developmental stage, whichever was greater. Percent viability was calculated by averaging the proportion of viable seeds in each of the three subsamples.
Number of Viable Seeds. The number of viable immature, intermediate and mature seeds was calculated by multiplying the number of seeds in each developmental stage by the percent viability of seeds in each respective developmental stage. Total viable seeds per plant were calculated by summing the number of viable seeds in the three developmental stages.
The experimental design for this study was completely randomized. Treatments were arranged in a 7 – 2 – 2 factorial arrangement, with an unclipped control group and seven timings/combinations of timings of defoliation, two defoliation intensities and two years. Individual plants were the experimental units.
Data were analyzed using the GLM procedure of SAS (SAS Institute 2009). Percent data, count data and continuous data that were not normally distributed were arcsine, square root and log10 transformed to stabilize variances and better approximate normal distribution of residuals (Steel and Torrie 1980; Kuehl 2000). Means and standard errors presented in the text and tables are from untransformed data. Analysis of covariance (ANCOVA) was used to compare responses among treatments. Percent canopy cover of sulfur cinquefoil and numbers of stems on the treatment plants were used as covariables in the analyses. Differences were considered significant at P ? 0.05.
The seed passage study was conducted at the Montana State University Bozeman Agricultural Research and Teaching Farm. Sixteen animals were used in this study; eight yearling goats (Spanish wethers) and eight yearling Targhee sheep wethers. All treatments were approved by Montana State University Animal Care and Use Protocal number AA-039. Animals were placed in individual metabolism stalls seven days before the beginning of the trial and fitted with fecal collection bags two days before the first fecal collections were recorded to familiarize them with the research protocol. Once daily, animals were fed ground grass hay in excess (9.4% CP; 64% NDF; DM basis), and 70 g of rolled barley (13% CP, 19% NDF; DM basis).
Sulfur cinquefoil seeds were collected from infested foothill rangeland near Bozeman, MT. Seeds were collected at two developmental stages. Immature seeds were collected post-flowering but pre-seed dispersal of sulfur cinquefoil (July 17). Mature seeds were collected when seedheads were beginning to dehisce (July 30). Immature seeds were light brown in color and the seed coats were somewhat doughy with no visible white “netting”. Mature seeds were dark brown to black in color, and the seed coats were hardened with clearly visible white “netting.” Collected seeds were purified by air-density separation, hand counted and stored in a seed closet at ~ 38 C until administered to the animals. Viability of the collected seed was determined by testing three subsamples of 20 seeds each from both developmental stages (immature and mature), using the tetrazolium (TZ) test (Grabe 1970). Each animal was orally gavaged with 5,000 sulfur cinquefoil seeds with four goats and four sheep receiving immature seeds, and four goats and four sheep receiving mature seeds. Total fecal collections began 24 hours after gavaging and continued for seven days.
Fecal collection bags were emptied once daily at 0800 hours, and bags were re-fitted. Total wet-weight of fecal output was recorded per animal. After thoroughly mixing fecal material within each collection bag, a 20-g sample was collected from each bag and dried at 100 C for 24 hours to determine moisture content. An additional subsample of approximately 100 g (wet weight) was collected and weighed from each animal and examined for sulfur cinquefoil seeds. Large clumps of feces were gently separated, and the fecal material was washed over a 425-micron sieve (# 40) till water ran clear. Fecal samples were then dried for 36 hours at 40 C (Wallander et al. 1995). Dried samples were sifted with a Ro-Tapp machine to remove fines (425 microns, # 40 sieve) and excessively large particles (850 microns, #20 sieve). Air density separation was used to further remove fines and concentrate the sulfur cinquefoil seeds into a smaller amount of dried fecal material. The remaining particles were hand sorted under a 10x magnifying lamp. All identifiable sulfur cinquefoil seeds were extracted and tested for viability using the TZ test. The number of viable seeds passed by animals was calculated as: # recovered seeds (corrected for total fecal output) and percent viability of recovered seeds.
Response variables included: 1) recovery of sulfur cinquefoil seed from sheep and goats; 2) viability of sulfur cinquefoil seed recovered from sheep and goats; 3) total number of viable seeds recovered from sheep and goats; and 4) viability of sulfur cinquefoil seeds over time till passage.
Experimental design was completely randomized with individual animals serving as the experimental units. Treatments were organized in a 2 -2 factorial arrangement with two animal species (sheep, goats) and two seed maturity stages (immature, mature). Data were analyzed as repeated measures using the MIXED procedure in SAS with day as the repeated measure and the covariance structure defined as AR(1) (SAS Institute 2009). Individual treatment animal was considered a random effect, animal species and seed stage were fixed effects and differences were considered significant at P ? 0.05.
Tannin Content of Plants
An additional 10 plants were randomly selected for tannin analysis during the pre-flower, flower and seedset phenological stages of sulfur cinquefoil. Plants were clipped at ground level, individually bagged and immediately placed on dry ice and transported to a freezer for storage. Plants were freeze-dried and ground in preparation for total tannin analysis by NIR-spectrometric calibration (Landau et al., 2004).
Objective 1 Results:
Yields of control plants averaged 3.5 g. Clipping to either 7.5 cm or 15 cm at any timing or combination of timings reduced yield of sulfur cinquefoil. Overall, the greatest reduction in yield occurred when plants were clipped during the flowering or seed ripe stages. For instance, clipping sulfur cinquefoil to 7.5 cm one time only at pre-flower reduced plant yield 50%, whereas clipping to 7.5 cm at seed ripe reduced plant yield by 80%. In general, plant yield was reduced more when plants were clipped to 7.5 cm than when clipped to 15 cm, regardless of the timing of clipping. When clipping occurred at flowering, yield was reduced 9% to 32% more by clipping to 7.5 cm versus 15 cm. When clipping occurred at seed ripe, yield was reduced 50% to 57% more when plants were clipped to 7.5 cm vs. 15 cm (Table 1).
Flower Production, Total Seed Production, Total Viable Seed Production.
Control plants averaged 41 flowers and 3,000 seeds per plant. Clipping to either 7.5 cm or 15 cm at any timing or combination of timings reduced flower production (Table 2), total seed production (Table 3) and total viable seed production (Table 5) compared with controls. The greatest reductions occurred when plants were clipped one time during the flowering or seed ripe stage. Clipping one time to 7.5 cm during either flowering or seed ripe completely eliminated all flower production (Table 2), seed production (Table 3) and viable seed production (Table 5). Clipping one time to 15 cm at flowering or seed ripe decreased flower production 99% to 100% (Table 2), decreased total seed production 99-100% (Table 3) and decreased production of viable seeds 99-100% (Table 5). In contrast, plants clipped one time at the pre-flower stage to either 7.5 cm or 15 cm decreased flower production compared to unclipped controls but still managed to produce some viable seeds in both years.
Objective 2 Results:
Viability of seed prior to livestock consumption averaged 36% for immature seeds and 76% for mature seeds. Individual sheep and goat weights averaged 47 and 32 kg, and animals consumed 1.0 and 0.6 kg, respectively, of ground hay daily for an average intake of 2.0% BW day-1.
Recovery of mature seeds peaked on Day 1 for sheep and Day 2 for goats; 97% of the recovered seeds were found within the first two days after ingestion (Figure 1). No seeds were recovered from goats after Day 5; however, seed was still being recovered from sheep on Day 7 (Figure 2). More seeds (immature and mature combined) were recovered from the feces of sheep than goats (1,924 vs. 1,336, respectively; P 0.05). Nearly one-half (46%) of the mature seed was recovered, while only 21% of the immature seed was recovered. Viability of immature and mature seeds recovered from sheep or goats on Day 1 did not differ from ungavaged seeds (P 0.05; Figure 3). However, by Day 2, viability of immature and mature seeds recovered from both sheep and goats was less than ungavaged seeds. By Day 3, viability of mature seeds recovered from sheep was less than the viability of mature seeds recovered from goats (13.3 vs. 30.6%, respectively; P 0.05). Overall, passage through the digestive tract of sheep or goats reduced the viability of recovered mature seeds by 64%, and the viability of immature seeds by 92%. For both sheep and goats, 94% of the viable immature seeds that were recovered and 98% of the viable mature seeds that were recovered, were recovered from Days 1 and 2 (Figure 4). No viable seed was recovered from either sheep or goats after Day 3.
Objective 3 Results:
A new, promising method for analyzing tannins was selected to be conducted at a USDA ARS laboratory in Virginia. Unfortunately, after waiting almost a year for the lab to get equipment up and running and standards developed, it was discovered that journals were not willing to publish the research using that methodology because of the large amounts of error associated with the sample analysis. Therefore, a different laboratory was contacted, samples were sent for analysis and a standard for sulfur cinquefoil was developed. Unfortunately, by now the integrity of the stored plant samples is questionable for tannin analysis as they were collected in 2006 and 2007. This objective will not be able to be completed in the time frame but will continue to be pursued in 2012.
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- Figure 4. Mean number of viable sulfur cinquefoil seeds recovered per animal from the feces of sheep and goats over a 7-day period following oral gavage of 5,000 immature or mature seeds per animal. Error bars depict the standard error of the mean (a = 0.05).
- Table 3. Number of immature, intermediate, and mature sulfur cinquefoil seeds at senescence (± SE) after clipping to 7.5 or 15 cm at different timings and combinations of timings on foothill rangeland in southwestern Montana.
- Table 5. Number of viable sulfur cinquefoil seeds at senescence (+ SE) after clipping to 7.5 cm or 15 cm at different timings and combinations of timings on foothill rangeland in southwestern Montana.
- Figure 2. Mean number of sulfur cinquefoil seeds recovered per animal from the feces of sheep and goats over a 7-day period following oral gavage of 5,000 immature or mature seeds per animal. Error bars depict the standard error of the mean (a = 0.05).
- Figure 3: Viability of immature and mature sulfur cinquefoil seeds recovered post-gavage from sheep or goat feces. Error bars depict the standard error of the mean (a = 0.05).
- Table 1. Aboveground biomass of sulfur cinquefoil plants at senescence (± SE) after clipping to 7.5 or 15 cm at different timings and combinations of timings on foothill rangeland in southwestern Montana.
- Table 2. Total number of sulfur cinquefoil buds, flowers, and seedheads at senescence (± SE) after clipping to 7.5 or 15 cm at different timings and combinations of timings on foothill rangeland in southwestern Montana.
- Table 4. Viability of immature, intermediate, and mature sulfur cinquefoil seeds at senescence (± SE) after clipping to 7.5 or 15 cm at different timings and combinations of timings on foothill rangeland in southwestern Montana.
The measurable impacts of this project are widespread, and the success of the project was evaluated in several ways, including methods of self-evaluation, external evaluation and outreach evaluation. Measurable deliverables produced and disseminated for information from this project include: 1) one field day, 2) twenty-four presentations at meetings/workshops/conferences/trainings, 3) two published outreach publications, 4) four abstracts in proceedings of professional meetings, 5) a Final Project Summary document (i.e., Western SARE Final Report), and 6) two refereed journal manuscripts; one submitted to Invasive Plant Science and Management and one to Rangeland Ecology and Management.
Through presentation of data and information from this project at meetings/workshops/conferences/field days, 24 hours of educational contact were made with groups that included livestock producers, landowners, county Extension personnel, county weed supervisors, land management agency personnel, researchers, students and concerned citizens. Information was disseminated to 843 individuals through presentations, handouts and field visits. Results of this project were also disseminated via hundreds of individual contacts with landowners and sheep producers.
Additionally, results from this project have been used to successfully leverage $350,000 in grant funds through the USDA Rangeland Research Program to conduct a large-scale grazing project in cooperation with the Confederated Salish-Kootenai Tribes to determine if sheep will consume sulfur cinquefoil. Preliminary results indicate that sheep readily consume the plant and are capable of reducing the viable seed introduced to the soil by 96% compared with controls. The funds received for this Western SARE project have laid the foundation for a body of research that will result in a complete targeted grazing prescription for sulfur cinquefoil. The thousands of acres infested with sulfur cinquefoil in Montana and elsewhere in western North America will be affected by the knowledge of how sulfur cinquefoil responds to defoliation. The land managers of the Confederated Salish and Kootenai tribes are highly interested in non-chemical ways to achieve weed control. Grazing managers are expected to adjust their grazing management plans to achieve the highest level of control possible, while minimizing the amount of sulfur cinquefoil seeds spread by their grazing animals. Additionally, sheep producers and landowners will benefit from the results of this study by increasing the effectiveness of sheep and goats for weed control and increasing the economical benefits to landowners in terms of another weed species being managed by grazing animals instead of herbicides. Ultimately, results of this project are expected to reach more than 10,000 people by way of meetings, training sessions and workshops (900 attendees); two popular press articles (5,000 readers); an abstract in a proceedings (1,000 readers); Project Summary document (200 readers); and two refereed journal articles (3,500 readers).
Educational & Outreach Activities
The results of this project have been presented numerous times to a wide variety of people. Specifically, results have been presented at the annual meeting of the Society for Range Management, the Western Region—National Association of County Agricultural Agents Professional Development Conference, the annual meeting of the Montana Weed Control Association and the Sheep Advisory Council for Montana State University. The results of this project have been incorporated into a training protocol for Bureau of Land Management employees and presented to approximately 320 employees attending nine training sessions between 2007 and 2011. Results were also presented to 90 participants at the Western Society of Weed Science Noxious Weed Short Course and at four different county weed education events in Montana, reaching nearly 300 people between 2007 and 2011. Finally, results were also highlighted in 2011 during a field day discussion among agency land managers and livestock producers about the potential for sheep grazing to control both sulfur cinquefoil and spotted knapweed.
The proposal included plans to receive external evaluation of the project from: 1) the Montana Sustainable Livestock Task Force (MSRLTF and 2) formal evaluation forms completed by participants at a field day workshop. The Montana State University Sheep Program Advisory Committee was substituted for the MSRLTF because the MSRLTF was inactive during the grant period. Formal evaluation forms were not distributed to field day participants because the field day was organized as an informal small group discussion among local leaders in noxious weed management. Participants included local livestock producers, herbicide applicators and personnel from Montana State University Extension, Salish-Kootenai Tribal College, the Confederated Salish and Kootenai Tribes, the U.S. Fish and Wildlife Service and the U.S. Forest Service. The proposal also included plans for external evaluation of the research by refereed journals. Two manuscripts are currently in review, one by Rangeland Ecology and Management and another by Invasive Plant Science and Management.
Frost, R.A., and J.C. Mosley. (In Review). Response of sulfur cinquefoil to defoliation. Invasive Plant Science and Management.
Frost, R.A., J. C. Mosley, and B.L. Roeder. (In Review). Recovery and viability of sulfur cinquefoil seed from sheep and goats. Rangeland Ecology and Management.
Frost, R.A. 2010. Featured weed: sulfur cinquefoil. Big Sky Small Acres 4(2):6-7.
Mosley, J. 2010. Targeted livestock grazing for vegetation management. Western Region—National Association of County Agricultural Agents Professional Development Conference, Helena, MT. [Invited]
Frost, R., B. Roeder, and J. Mosley. 2009. Recovery and viability of sulfur cinquefoil seeds post-consumption by sheep and goats. Montana State University Sheep Program Highlights, Department of Animal and Range Sciences, p. 35-37.
Frost, R.A., and J.C. Mosley. 2009. Effects of timing and intensity of defoliation on yield and seed production of sulfur cinquefoil. Abstract. Montana Weed Control Association Annual Meeting, Billings, MT. [Invited]
Frost, R.A., J.C. Mosley, and B.L. Roeder. 2009. Recovery of sulfur cinquefoil seed ingested by sheep and goats. Abstract. Society for Range Management Annual Meeting. Albuquerque, NM.
Frost, R.A., and J.C. Mosley. 2007. Defoliation effects on yield and seed production of sulfur cinquefoil. Abstract. Society for Range Management Annual Meeting, Reno, NV.
Frost, R., and J. Mosley. 2007. Is sulfur cinquefoil a candidate for control with sheep or goats?, p. 19-20. In: Montana Wool Growers Association Sheep Advisory Committee Report, Montana State University, Bozeman.
There are two potential ways to defoliate sulfur cinquefoil; livestock grazing and mowing. Targeted grazing by livestock on rangeland is estimated to cost between $4-8/acre in Montana (Lisa Surber, Montana Sheep Institute, personal communication). More intensively managed contract grazing can cost more depending on the number of animals, the challenge of providing water and herders, and the complexity of the plant community. Nevertheless, targeted livestock grazing generally costs less than the $125.00/ha ($50/acre) that Brown and others (1999) calculated to mow rangeland infested with spotted knapweed. Comparatively, the cost of treating sulfur cinquefoil with herbicide is near $21-30/acre. Therefore, depending on which method is chosen for defoliation, mowing or grazing, cost of control could be double that of herbicide (mowing) or 1/3 that of herbicide (targeted grazing). Economic returns would be based primarily on the increased livestock production capable on weed-free rangeland. Other possible economic returns include improved wildlife production and habitat enhancement.
Risks are inherent in any vegetation management project. Specific risks for targeted grazing include: sheep not eating the target plant, risk of disease transfer to wildlife and risks of excessive livestock losses due to predation. Similarly, mowing is unable to be applied on some sites because of rocks, shrubs or trees, or steep slopes that may prevent mower operation. Any areas that do not receive defoliation by either livestock or a mower retain seedheads that can produce live seed, thereby replenishing the weed population. Because sulfur cinquefoil is a long-lived perennial, both grazing and mmowing will require multiple years of treatment to deplete the eedbank and a long-term commitment to manage the existing population.
Many producers currently involved in targeted grazing have added sulfur cinquefoil as a potential plant to be targeted in their grazing projects. Hundreds of Bureau of Land Management weed personnel, private landowners, Extension educators and county weed coordinators in Montana and western North America now recognize that there are more options available for managing sulfur cinquefoil on rangelands. Potentially all of the 1 million acres of U.S. rangeland currently infested with sulfur cinquefoil could be impacted with this new knowledge. Furthermore, the sheep and goat industry in Montana and western North America could benefit from an increased forage base, as well as expanded economic opportunities for targeted grazing projects. Recommendations for day to day operations are to defoliate sulfur cinquefoil during the flowering or seedripe stages and, for livestock that consume viable sulfur cinquefoil seed, to drylot these livestock for four days before moving them to uninfested areas. For example, a targeted grazing project near Missoula, MT, now manages their sheep so that infestations of sulfur cinquefoil are grazed before seeds become viable to prevent spread to other areas of the grazing unit. While our research did not directly test the passage of sulfur cinquefoil seeds through the digestive tract of cattle, it is highly probable that cattle are capable of spreading viable sulfur cinquefoil seeds. Farmers, ranchers and land managers should exercise care when transporting animals if they come from an area where sulfur cinquefoil is present and currently producing viable seeds.
Areas needing additional study
Given the knowledge gained in this project, the next logical step is to conduct actual grazing and mowing trials specifically designed to decrease the vigor and reproductive ability of sulfur cinquefoil. Additional research should focus on the diet selection of livestock, and whether supplements can enhance intake of the plant. An assessment of soil seedbank dynamics in response to repeated defoliation would help determine the number of years defoliation would be needed to exhaust the soil seedbank of viable sulfur cinquefoil seeds. Ultimately, research is needed to assess the effects of repeated defoliation of sulfur cinquefoil on plant community composition within sulfur cinquefoil infestations.