U. affinis is multivoltine and overwinters as a larva in knapweed … Leaves: Gray-green, covered in rough hairs, and deeply divided. This weevil prefers hot, dry sites with loose, well-drained, coarse soils. micranthos Photo courtesy Bob Case. By 1920 the plant was well established in several infestations near Missoula, Montana, and now it has spread to 5 million acres just in this state. Spotted Knapweed: note the black markings on the green, just below the flower blossom – these are the “spots”. The Conservation Services Division provides technical and financial support, leadership and statewide coordination, and regulatory oversight to public/private landowners and … Biocontrol in Your Backyard; How To. Displacement of native vegetation may impact biodiversity. Take a photo of the site so you have an image to compare with several years following the weevil release. A combination of seedhead and root weevils greatly reduced the spotted knapweed infestation pictured on the left. Do not worry about depleting the spotted knapweed weevil population. Spotted knapweed (C. maculosa) first arrived in this country in about 1893 and quickly spread across both western states and eastern states. Diffuse knapweed showed significant declines at 14 of 15 sites; spotted knapweed declined at three of four sites. It was first recorded in North America in 1893 and in Minnesota in 1918, likely introduced as a contaminant of alfalfa seed. Seedhead weevils are widely distributed in Minnesota so they are only released at sites where they are not already present. The developing larvae in the roots use precious plant resources and damage the roots. We were convinced that the successful biocontrol of spotted knapweed would require a complex of natural enemy species. View All. Dead plant material can increase risk of fire. Reporting. So, much of the spotted knapweed work in the 1980s was focused on the survey, testing, collection, and introduction of Eurasian natural enemies of the weed. Centaurea stoebe ssp. Spotted Knapweed Diffuse Knapweed Adult Larinus minutus Releasing Larinus minutus Larinus minutus, up close knapweed with a slight preference for diffuse knapweed. Larvae are legless, have brown heads and c-shaped creamy white to yellow bodies. These introduced bugs have done wonderful things. Click on each species to view county distribution maps. spotted knapweed sites •Joey Milan with BLM and Dr. Mark Schwarzlaender with U of I working on analysis •We have analysis challenges –We were not “starting at the beginning;” most spotted knapweed biocontrol agents were released in 1980’s and 1990’s –With 20-30 years of impact, last 6 … Videos; Field Guide; vault About About Us; FAQ; Contact Us Distribution Maps Search by weed or insect . Roots and seedheads of spotted knapweed were collected from 45 sites in western Montana over a two-year period, and monitored for insect emergence (photo, right). Is it one large continuous patch or several smaller, isolated patches? As a result, the plant is weakened or killed. Introduced from Greece and Romania and originally released in the USA in 1991. Spotted knapweed, Centaurea maculosa, was introduced to America via contaminated alfalfa and clover seed in the 1890s; it made its way to Canada in 1893. Diffuse knapweed is a shortlived, non-creeping perennial, a biennial, or occasionally an annual that reproduces and spreads solely from seed. Releasing them is simple. Colorado Parks and Wildlife. Both of the Knapweed Flowerhead Weevils are winter cold hardy and yet thrive in hot, dry summer knapweed environments. Do not select sites that will be mowed. 711 TTY, © Copyright 2020 Minnesota Department of Agriculture, Farm, Property, Real Estate Listing (MN FarmLink), Agriculture Chemical Response & Reimbursement Account, Agricultural Best Management Practices (AgBMP) Loan, Agricultural Growth, Research & Innovation (AGRI) Program, Sustainable Agriculture Demonstration (AGRI), More Business Development, Loans, Grants Topics, Minnesota Ag Water Quality Certification Program, Certified Testing Laboratories (soil & manure), Fertilizer Tonnage Reporting & Inspection Fees, Pesticide Dealer Licensing & Sales Reporting, Biology and Biological Control of Knapweed (PDF). From Austria, Hungary, and early summer weed species favor and establish on! Markings on the top of the Pacific Northwest that eradicates plants around it may... Knapweed would require a complex of natural enemy species or mark the spot with a.... 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