Mealor identifies new weed species as potentially harmful and invasive for Wyoming rangelands

Casper – At the Wyoming Weed and Pest Council Fall Conference and Business Meeting, held on Nov. 6-8 in Casper, UW Weed Extension Specialist Brian Mealor looked at weed species that haven’t been on the radar of the weed control community, but may pop up as invasive in the future.
    “A few of these weeds are currently spreading into new areas and are potentially problematic,” commented Mealor, naming Russian sage, white horehound and Ventenata Grass, among others.
Russian sage
    “We think this next one might be one of the next big weed species we have to deal with – Russian sage,” Mealor said. “It seems like everyone plants it in their landscaping because it actually grows.”
    “The horticultural catalogs have a suite of characteristics describing why we should plant it,” he explained. “It is drought tolerant, it establishes, it grows quickly, and it is resistant to deer and rabbit browsing.”
    “It sounds like a fantastic horticultural plant,” Mealor added, “but it also sounds like a fantastic weed.”
    While many are using the plant as an ornamental, he said it is starting to spread out of flowerbeds into yards and surrounding areas. Additionally, there are a number of options for ornamental species rather than Russian sage.
    Using a recognized Weed Risk Assessment method for determining whether or not plants should be introduced as ornamentals, Mealor did a basic analysis of Russian sage. The results of the analysis recommended that the species be rejected for adoption as a horticultural or ornamental species.
    “We can’t reject it now, because it has already been introduced, but what we can do is be aware of it and keep an eye out for it,” he mentioned.
    He also warned that research is needed for control mechanisms for the species.
    “We just don’t know what works for Russian sage,” Mealor said. “Maybe we need to do some work to get ahead of it.”
White horehound
    White horehound is another species of concern.         Like Russian sage, white horehound is a member of the mint family, and may pose control concerns.
    “There are a lot of occurrences of this plant in Wyoming,” Mealor showed. “It is more widely distributed in the southeast.”
    He also mentioned that the plant seems to be particularly prone to spreading after fire.
    As an example, Mealor said, “Three years ago, Wind Cave National Park reported 10 acres of the plant. They had a fire move through, and this year they reported 18,000 acres of the plant. There is potentially a relationship between fire and the species.”
    Though impacts are hard to define, he said that the rapid spread of the plant may be of concern.
    Mealor added that similar to many aromatic plants, white horehound is likely not palatable to livestock consumption, and the species may be one to keep and eye on.
Ventenata grass
    “This is one of the weeds that worries me the most,” commented Mealor of Ventenata grass. “We recorded it in the state in the 1980s in Sheridan County close to the border.”
    While Mealor was unable to locate the species this summer, he noted that it has appeared in Idaho and is problematic in that state.
    “Ventenata grass is a North African grass,” he explained. “It is an annual grass that has come to dominate the Great Basin.”
    When compared to cheatgrass, he mentioned that there are number of similarities between the species, but weed specialists in other part of the country have noted that they would prefer cheatgrass to this species.
    “Cheatgrass is at least good forage early in the spring,” he said. “Palatability of Ventenata grass is nothing.”
    Plant structure is also similar to cheatgrass, though the plants matures a little later, more in conjunction with the native perennial grasses, making it harder to control.
    “The awns are curved, whereas cheatgrass awns are straight,” Mealor said, also noting differences in the spikelet of the plant.
    “I worry we might just be driving by it,” Mealor added, noting that any doubt about plant identification should be checked out. “Like everything else, false positive are better than just driving by.”
    Mealor addressed several other species, including Dame’s Rocket, Moth Mullein and Rush skeleton weed in the Extension Column of the Nov. 3 edition of the Wyoming Livestock Roundup.
    Saige Albert is managing editor of the Wyoming Livestock Roundup and can be reached at saige@wylr.net.