Recipient Organization
UNIVERSITY OF CALIFORNIA, DAVIS
410 MRAK HALL
DAVIS,CA 95616-8671
Performing Department
Plant Sciences
Non Technical Summary
Throughout the Central Valley and foothills of California, as well as the rangeland ecosystems of other western states, a major factor detrimental to ecological function, wildlife and their habitat, and forage production is the invasion by winter-annual grasses. In particular, barb goatgrass, cheatgrass or downy brome and medusahead, as well as numerous noxious thistles now dominate more than 70 million acres throughout the western US and continue to rapidly spread. These species, particularly the annual grasses, can impact promote frequent dangerous and harmful fires. In addition, both noxious grasses and thistles can aggressively displace more desirable forage species resulting in decreased forage quality and quantity. They also dramatically reduce plant diversity and richness, negatively affect habitat for wildlife, accelerate erosion, and pose a serious risk to human life by promoting out-of-control wildfires, often near urban areas. Their environmental impacts are extensive and their economic impacts have been estimated to be in the billions of dollars a year in the US.While there are control options developed for many of these species, few studies have considered how management can be incorporated into an Integrated Pest Management (IPM) strategy or how these species can be controlled for organic production systems. For example, one of the largest producers of organic artisan cheese in the region (Cowgirl Creamery) has expressed concern over the expanding infestations of woolly distaff and purple starthistle on the rangelands and pastures of dairies that supply them milk. In Marin County, more than 75% of the 27 dairies are in organic production as are over 50% of the dairies in Sonoma County, and the spread of these invasive non-natives is threatening their ability to comply with pasture-derived forage requirements in the National Organic Program's pasture rule. In addition, several beef producers are organic and rely heavily on the forage produced from rangelands. Without adequate forage, they are forced to purchase expensive organic feed, affecting the economics of their operations.The primary goal of this project is to assist conventional and organic ranchers and land managers in finding effective and economical solutions to some of the most important thistle and noxious annual grass problems in California. Two thistles, in particular, woolly distaff thistle and purple starthistle, have severely impeded the capacity to produce adequate forage for economic sustainability of pastures and rangelands in the North Coast and have compromised land managers' ability to maintain organic certification. This latter point is critical to North Coast counties. For the noxious annual grasses, barb goatgrass is expanding its range at an alarming rate. Though we have shown with previous research that prescribed burning can provide a very effective management tool, this method is not generally practical and can also be unreliable with fuel is not sufficient to allow for a second year burn. Thus, additional control options need to be developed for this noxious annual grass. In this proposed project, our first objective is to conduct a survey of land managers and owners to determine what options they have used to manage distaff thistle, purple starthistle, and barb goatgrass. We expect that, although most land managers have not been successful in controlling these species, others will have demonstrated different levels of success using a variety of methods. This will give us a baseline to establish subsequent experiments.We anticipate that our management experiments will emphasize mowing timing and frequency, comprising the organic component of our project, and optimization of application rates and timing for chemical control using both industry standards and organic herbicides. We also expect to test integrated management approaches combining mechanical and chemical methods. Based on survey results, we may test other techniques such as grazing management, prescribed burning, and desirable plant reseeding. Because both thistle species are very spiny and barb goatgrass is high in silica content and has long awns associated with its flower head, we do not expect grazing management to be a widely used control option. Grazing management regimes will be evaluated to determine the best timing of grazing to maintain or increase forage to outcompete these undesired species. These experiments will be conducted and repeated over a period of three years. The long-term goal is to provide one or more effective options for the many organic and conventional land owners and managers, ranchers, and growers faced with managing these noxious species. As another benefit to reporting the results of these experiments, our publications should provide evidence that will facilitate approval of low-risk herbicides for the management of these and other invasive thistles in the coastal counties.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Goals / Objectives
A number of non-native plant species can cause significant problems on rangelands, pastures and wildlands. They decrease forage quality and quantity, alter fire regimes, reduce wildlife habitat as well as plant and animal biodiversity, and change soil water and carbon dynamics. Their environmental impacts are extensive and their economic impacts have been estimated to be in the billions of dollars a year in the US. Unlike most agricultural weeds, which are herbaceous annuals or perennials, noxious weed species in non-crop areas can be annuals, biennials, short or long-lived herbaceous perennials, shrubs, or trees. Although they are represented by several plant families, the largest number of noxious weed species belongs to the family Asteraceae (sunflower), and within this family the most problematic species include thistles, such as yellow starthistle (Centaurea solstitialis), Malta starthistle (Centaurea melitensis), woolly distaff thistle (Carthamus lanatus), bull thistle (Cirsium vulgare), Canada thistle (Cirsium arvense), musk thistle (Carduus nutans), purple starthistle (Centaurea calcitrapa), Scotch thistle (Onopordum acanthium), and artichoke thistle (Cynara cardunculus), and the Poaceae (grasses), particularly medusahead (Taeniatherum caput-medusae), barb goatgrass (Aegilops triuncialis), and downy brome (Bromus tectorum).The primary goal of this project is to assist conventional and organic ranchers and land managers in finding effective and economical solutions to some of the most important thistle and noxious annual grass problems in California. Two thistles, in particular, woolly distaff thistle and purple starthistle, have severely impeded the capacity to produce adequate forage for economic sustainability of pastures and rangelands in the North Coast and have compromised land managers' ability to maintain organic certification. This latter point is critical to North Coast counties. For example, one of the largest producers of organic artisan cheese in the region (Cowgirl Creamery) has expressed concern over the expanding infestations of woolly distaff and purple starthistle on the rangelands and pastures of dairies that supply them milk. Furthermore, in Marin County, more than 75% of the 27 dairies are in organic production as are over 50% of the dairies in Sonoma County, and the spread of these invasive non-natives is threatening their ability to comply with pasture-derived forage requirements in the National Organic Program's pasture rule. In addition, several beef producers are organic and rely heavily on the forage produced from rangelands. Without adequate forage, they are forced to purchase expensive organic feed, affecting the economics of their operations.For the noxious annual grasses, barb goatgrass is expanding its range at an alarming rate. Though we have shown with previous research that prescribed burning can provide a very effective management tool, this method is not generally practical and can also be unreliable with fuel is not sufficient to allow for a second year burn. Thus, additional control options need to be developed for this noxious annual grass.
Project Methods
Study sitesThis study is proposed to be conducted on multiple sites within the North Coast region of California and the foothills of the Central Valley. The North Coast region is where many of the most problematic thistles occur and barb goatgrass, as well as medusahead, are most prominent in the Central Valley foothills. Each site will have replicated studies. Sites will be determined with the help of collaborating UC Farm Advisors who are in contact with landowners or land managers that are willing to allow research within their sites.Procedures for thistle controlWhile a great deal of attention has been paid to the integrated management of some thistles, particularly yellow starthistle, many other species have received far less attention. While it is expected that herbicide control options that effectively manage yellow starthistle, or other well-studied thistles, will be equally effective on less studied thistle species, this may not always be the case. For example, effective control of particular species may depend on herbicide application timing and rates different from the practices used for yellow starthistle. In the northern coastal counties of California, two of the most important noxious weedy thistles include a winter annual (woolly distaff thistle) and a short-lived perennial (purple starthistle). Many areas in these coastal counties prohibit the use of herbicides for the management of noxious and invasive weeds, but growers, ranchers, and other land managers have no alternative management options. These experiments are designed to provide conventional chemical, organic, and integrated pest management options for land managers and ranchers faced with economically important levels of infestation with either of these two thistles.Survey of land managers. We will develop a simple survey to mail, email, and distribute at a variety of meetings. The ranchers and land managers will be asked if they have a problem with either distaff thistle or purple starthistle. If they indicate they are a problem on their lands, we will ask what practices they have used to manage them, giving them a number of choices, e.g., herbicides, grazing management, prescribed fire, and mechanical controls, as well as asking if they have used any options in combinations. Survey respondents who indicate they have used some control method for distaff thistle or purple starthistle and who also note a willingness to be contacted will be called or interviewed in person. These responses will be critical in designing our future field experiments within these counties. Mechanical control. While cutting at ground level was found to be an effective means of control for yellow starthistle, this method is impractical, especially in steep, rocky terrain. In contrast, field mowers are typically set four inches above the soil surface. Thus, we will use a string weed whip at a four inch height to conduct our mowing trials on distaff thistle and purple starthistle. Treatments will include uncut controls and one or two mowings conducted when spiny flower buds are present but before viable seed are produced. This generally corresponds to spring treatment timing, with a second mowing when plants recover (probably early summer). The experiment will be a randomized complete block design with four replicates and will be repeated in the following year. Each plot will be 5 by 10 feet. Thus, there will be 4 replicates x 3 mowings (uncut, mowed once, mowed twice) for a total of 12 plots per trial for each species and year. Plants will be allowed to recover after the mowings and will be evaluated at the end of the season for percent cover using three 1-m2 quadrats per plot. In addition, flower production, plant height, and noxious thistle biomass (three 0.25-m2 quadrats per plot) will be measured. We anticipate that mechanical control will be more effective for the annual, distaff thistle, than for the short-lived perennial, purple starthistle.Herbicide treatments. Based on our previous results on the control of other thistle species, the herbicides clopyralid, aminopyralid, and aminocyclopyrachlor or aminocyclopyrachlor in combination with chlorsulfuron are expected be the most appropriate options for management. Clopyralid and aminopyralid have no grazing restrictions and these will be important to ranchland managers. Aminocyclopyrachlor was recently registered in California. All these compounds have both foliar and soil residual activity and should provide control of emerged and later emerging seedlings. In addition, they have little activity on most grasses, which we expect to increase following treatment. We will include two timings and two rates of each of these products plus untreated controls. Plots will be 10 x 30 ft, with four replications in randomized complete block arrangements, totaling 72 plots per site and per species (4 replicates x 2 timings x 2 rates x 4 herbicides plus untreated controls). These experiments will also be repeated for two years. In addition to testing conventional herbicides, we will test a couple of organic products. Currently, all organic herbicides are considered fast-acting contact products and are not likely to provide very effective control of purple starthistle, and perhaps not even for distaff thistle. Integrated approaches. If it is possible to combine herbicides with prescribed burning in an integrated management strategy, we would include this option in the prescribed burning trial. In the past, we have found that burning, followed by clopyralid or aminopyralid, is the most effective treatment for yellow starthistle. A similar result would be expected for distaff thistle, although it may be more difficult to manage the perennial purple starthistle using this combination. Data collection. Data collection for all the control methods, except mowing (already described), will include percent cover of all important species, as well as an evaluation of the vigor and reproductive potential of the invasive thistles. We will perform vegetation cover evaluations and biomass sampling in the summer, after both thistles have already flowered. In the chemical control trials, three 1-m2 quadrats will be randomly thrown in each plot, where cover of each plant species will be visually evaluated. In these plots, we will randomly toss 1-m2 quadrats for vegetation cover sampling as described above, and 0.25-m2 quadrats for biomass samples of thistles and desirable species. Biomass will be clipped at 7.5 cm above the ground, bagged, dried at 60oC for 1 week, and weighed. Results from cover quadrats and biomass quadrats will be averaged for each plot.Procedures for barb goatgrass and other noxious annual grass controlHerbicide treatments. Based on our previous results on the control of medusahead we have shown that higher rates of growth regulator herbicides, including aminopyralid, and aminocyclopyrachlor or aminocyclopyrachlor in combination with chlorsulfuron will give effective and selective management. This is unusual, as these herbicide generally target broadleaf species. Similar experiments have not been conducted on barb goatgrass. In addition, it has been showed that much lower rates of aminopyralid caused sterilization of Japanese brome plants without killing the foliage. The authors suggested that growth regulators might be used to control invasive annual grasses by depleting their short-lived seed banks. We will expand this concept by testing it on both barb goatgrass and medusahead. If successful, this would not only provide more economical control of these grasses, but would leave the foliage for foraging in the year of treatment. Similar experimental design, including plot sizes, replicates, and analysis, will be used as was described for the thistle herbicide experiments above.