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Weeds
Volume 57 Number 21 Date 11/08/2012 INVASIVE WEEDS - A large-scale weed survey was conducted in 2012 at 598 locations. Presence/absence data was collected for three important invasive species: spotted knapweed, common tansy and black swallow-wort. The target weeds were selected based on the need for more comprehensive baseline distribution records to inform future biological control efforts. Spotted knapweed was the most common of the three species, found at 12% of surveyed sites, while common tansy was noted at 10% of sites. Black swallow-wort was not observed at any of the 598 sites. Besides showing presence or absence, the survey also revealed pronounced regional variation in weed pressure. Most spotted knapweed, for example, was found in the central and northwestern districts where an average of 46% and 26% of sites were infested, respectively. Common tansy was documented most often in the north-central (33%) and northwest (29%) areas. Results of the survey indicate invasion pressure from both spotted knapweed and tansy is highest in the central and northern areas of the state and this is where future introductions of biological agents should be focused. -- Clarissa Hammond, DATCP Pest Survey 
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