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Gearing Up for Spotted Knapweed Control

By Christine Gelley
 
It is never too early to think about weed control in Ohio pastures. While it may only be February, there are steps you can take to get prepared for combatting weeds in 2019.
 
Extension Educators across Ohio are actively training new and experienced private and commercial pesticide applicators on integrated pest management, safe handling of pesticides, responsible record keeping, and new rules and regulations. To learn more about training and recertification opportunities for pesticide applicators, visit www.pested.osu.edu.
 
Those of us on the Eastern side of Ohio are gearing up to address a new aggressive weed in our pastures, CRP land, and roadsides. Spotted knapweed has been creeping its way into our landscapes over the past few summers. Along with traditional education about pasture management and weed control, additional help is available for landowners who spot spotted knapweed on their property.
 
The Spotted Knapweed Treatment for Ohio Producers (STOP) Project is funded through the Regional Conservation Partnership Program (RCPP), which is administered by the Natural Resources Conservation Service (NRCS). Landowners of Noble, Guernsey, Muskingum, and Morgan County are eligible to apply for cost recovery funds to treat spotted knapweed in pasture and hayfields.
 
County Soil and Water Districts and OSU Extension are active partners in the program. We hope to increase awareness of spotted knapweed in our landscapes and provide educational resources on how to control its spread. Many producers do not see it in the first year and then misidentify it in year two.
 
The color of the flower is similar to that of red clover, the growth habit is similar to chicory, and the flower shape is similar to Canada thistle and ironweed. However, the combination of growth habit, color, and flower shape is unique to spotted knapweed.
 
Step #1 for treatment of spotted knapweed is accurate identification. Spotted knapweed (far left) is often confused on first glance with other flowers like red clover, chicory, or ironweed. Growth habits are drastically different between all of these plants.
 
The flower is pretty and attractive to pollinators. However, it should not be intentionally propagated. There are many other plants that could be incorporated into the landscape for this purpose which are not considered threatening to agricultural production as a whole.
 
This weed is similar to a biennial, in that the first year of growth there is no flower. The plant will flower in the second year and continue to flower in the years following. It is a prolific seed producer, so if knapweed is ignored in year two, you can experience a population explosion in year three.
 
Knapweed is a forb that is responsive to multiple broadleaf herbicides. Mowing is marginally successful. It does help prevent the development of seed, but it is able to flower below the height of the mower deck. Chemical treatment has been successful in grass pastures of our region if timed appropriately. There are biological controls being developed for spotted knapweed too, but they are primarily used in the Western States that have been dealing with this weed for decades already. Demand is high and supply is low.
 
Knapweed in the basal rosette stage
 
The mature seed heads resemble Canada thistle, a tight cluster of seeds with a fluffy pappus attached. The pappus helps the seed move with wind, water, animals, and vehicles.
 
Knapweed is aggressive because it has few natural predators in Ohio. Animals are unfamiliar with it and it thrives on marginal soils. It can outcompete weak stands of desirable plants for nutrients.
 
The best tools for spotted knapweed control are early detection and early action. Hand pulling and spot spraying young plants that are few and far between can be effective on new invasions. However, heavy infestations will likely take a more creative and lengthy approach to treat.
 
You can learn more about spotted knapweed in Ohio on YouTube. Extension Educators, Clifton Martin of Muskingum County and myself, broadcasted an informational interview about spotted knapweed as part of a video series called “Forage Focus” in September 2018. It can be viewed at www.go.osu.edu/knapweedohio2018.
 
If you come across something you suspect might be spotted knapweed, please contact your County Extension Office for assistance with identification.
 
To learn more about the STOP Project or to submit an application, visit your local USDA Service Center or visit the NRCS website and select “Get Started with NRCS”.