Plan to attend the next Nevada Weed Management Association (NWMA) conference. NWMA is hosting its 2015 conference, “Catalyst for Change: Opening the Conversation for Changing Nevada’s Noxious Weed Program”, in conjunction with a Medusahead Symposium, October 26-29, at the Nugget Hotel & Casino in Sparks, Nevada. More information regarding the symposium and conference can be found at NWMA’s website. Come be part of the discussion, learn about noxious weeds, weed management and engage in Nevada weed management issues. Presenters for these sessions have been invited from throughout Nevada, as well as several neighboring states. Breakout session that qualify will allow participants to earn continuing education units (CEUs) required for the renewal of applicator licenses, including a training on law.
EDDmapS map of Canada Thistle
Joy Paterson, Lyon County Extension Educator and UNCE–IPM team member, and Jamie Abbott, Noxious Weed Coordinator for Nevada Department of Agriculture (NDA) will be teaching a half-day workshop on EDDmapS including the website, data upload including how to upload data from other mapping software, map creation, smart-phone or tablet applications and other user features of the software. Tablets will be available to use during instruction, but participants are encouraged to bring their own laptops, tablets and smartphones. EDDmapS should be downloaded prior to the course. The course will include time for Joy or Jamie to assist with questions about your data or how to use the application or computer interface. Reporting noxious weed locations is important for use in demonstrating the extent of noxious weed issues in Nevada and using EDDmapS allows information to be shared nationwide.
Hope to see you there!
Musk Thistle Plant
Musk Thistle, Carduus nutans, is a biennial, noxious weed that occurs throughout the United States. EDDmaps reports it in Lyon county, where I took these photos. A rosette forms in the first year and the second year the plant will bolt and form a flower heads. The plant is solitary and does not spread vegetatively. The stems and leaves have spines. The flowers are white to pink or purple with spine tipped bracts at the covering the receptical, or base, of the flower. The flower heads often “nod” with the stem bending and the head tilting over to one side. Carduus species can hybridize, so morphological characteristics vary.
Musk Thistle Flower
Musk Thistle Rosette
Confirm your identification prior to treating an area. Native thistles can appear very similar to musk thistle, but pose no environmental or economic threat in agricultural, grazing or natural areas.
To control musk thistle, it is best to remove the plant in the first year, when it is a rosette and has not flowered. The tufted seeds spread easily with wind. Thistles only reproduces from seed, so mechanical control can be very effective. Mechanical control is most effective when the tap root is disturbed and destroyed. Once the plant goes to seed, the area will need to be monitored every year and any rosettes destroyed. Seeds readily germinate in disturbed soil, so plan mechanical controls in the spring prior to flowering from June to September.
Musk Thistle with “Nodding” Flower Heads
Biological control agents have been released for this weed in Nevada, but are no longer available for distribution and release. If you have a large contiguous patch, where other controls are not an option, you can monitor for the biological control agents by looking for the larvae in the root crown or seed heads. The spines and the detestable flavor of the plant prevent grazing by most animals, so control by grazing is not effective.
This time of year, the plants will have already gone to seed. If you notice the remainder of the plants, mark the location and plan to revisit the area in the spring to scout for rosettes. Prevention of further establishment is key to preventing this noxious weed from causing economic or environmental harm.
Close-up of a yellow starthistle, showing the star-shaped spines around the base of the flower
Yellow starthistle is an annual plant with yellow flowers with long white spines covering the plant. Under a microscope, the surface of the plant also has thin curly hairs that cover the surface and cause a grey appearance to the stems and leaves. The plant can vary greatly in size from very short, 6 inches, to over 5 feet with stems that appear winged. It has a deep taproot and with many branched stems. Disturbance allows yellow starthistle to rapidly colonize areas. Once established, it is able to rapidly remove the moisture from the soil, preventing other plants from establishing. Ideal habitats are dry and sunny. Flowers are very productive, producing thousands of seeds per plant. Horses should not graze in areas where yellow starthistle is present. It can cause chewing disease, which is fatal for horses that eat the plant.
Side view of the flower head and stem, notice the winged appearance of the stem, long yellow spines and greyish appearance of the plant surface
Distribution of yellow starthistle is broad across the United States. Spreading in our area of Nevada anecdotally follows primarily riverways and weed management work along the Carson river watershed in Carson County has focused on preventing spread further downstream. It has been reported 11 times in Lyon County by EDDMapSWEST and is currently unreported by the USDA PLANTS database. While these reports were in Southern Lyon county, it is likely to spread into Northern Lyon county via waterways or highways. It has been reported to infest between 10 and 15 million acres in California. The photos in this blog were taken in California, where I observed yellow starthistle infesting roadways, fields, irrigation ditches and encroaching into natural areas.
Yellow starthistle growing on dry roadside
Management of yellow starthistle is most effective when weeds are managed prior to going to seed. Frequent scouting in areas of potential spread, repeated scouting in treated areas and removal of plants prior to seeding. Small patches are best handled with hand pulling ensuring that all flower heads are contained to prevent spread at the disposal location. Larger patches have a variety of control options, but without re-vegetation with desirable plants, yellow starthistle can quickly re-establish. Prevention of establishment relies on effective reporting and treatment of infested areas. Email photos of suspected yellow starthistle for identification confirmation.
Bolted Scotch Thistle Plant Prior Flowering
Scotch Thistle Head Prior to Flowering
Invasive weeds are an issue anywhere people travel or transport things. Every month, I will highlight a weed that is either not established or is in low abundance in Lyon County. Verified records of these weeds are very helpful to weed managers and Nevada Department of Agriculture. If you see these plants, you can report them directly to Nevada Department of Agriculture, using the app EDDmaps, or email me photos and a location. Invasive weeds are everyone’s problem, so help keep them from invading your neighborhood and report them.
Scotch thistle, Onopordum acanthium, is a large spiny plant with pink to purple flowers. Thistles are difficult to identify, so confirm your identification before destroying thistles. Native thistle plants are declining for many reasons and need to be protected. Like most thistles, Scotch thistle is biennial and is a rosette of leaves the first year and bolts into a tall plant with flowers the second year. The rosette stage is difficult to identify. The bolted plant can be very tall, up to 6 feet. Characteristics of the leaves, flowers or seeds can distinguish it from other thistles.
Current distribution maps (EDDmaps or USDA Plant Database)of scotch thistle is broad across the United States. EDDmaps reports Scotch Thistle in Lyon county. I observed it while hiking in southern Lyon county. It is listed as a category B weed by Nevada Department of Agriculture. Scotch thistle can be controlled by pulling up the plant or removing the flower heads by cutting or mowing before it goes to seed. Nevada Department of Agriculture has recommendations for chemical control of Scotch thistle.
Field Bindweed Flowers
Field Bindweed at the Lyon County Cooperative Extension Office
After assisting with the biological control release on field bindweed, I have started to pay attention and I am noticing it more places. I even found it at our office. University of Nevada Cooperative Extension publication “Managing Field Bindweed” has useful information for managing bindweed; if you ever find it hiding in plain sight, like we did. It is a vining plant, with white to pink trumpet shaped flowers and arrow shaped leaves. Not sure if it is bindweed? Send me a picture.
Bindweed is difficult to control, once established. Small areas of infestation should be aggressively managed to prevent spread. Mechanical control requires removing or destroying all the green above ground parts and going several inches into the soil profile to remove the rhizomes as deep as possible. Smothering or solarization will only work if the entire plant is covered long enough to starve below ground portions of the plant. Chemicals can also be effective; however, the area should be monitored and re-treated if any return growth is observed. Biological control is an option for large patches that cannot be treated other ways. Agents have been released in Nevada, but have had limited success establishing.