Palmer amaranth–a fast-growing, challenging to control noxious weed that significantly reduces crop yields—was first found in Minnesota in September 2016 in conservation plantings sown with Palmer amaranth contaminated seed mixes. Minnesota Department of Agriculture (MDA) designated Palmer amaranth as a Prohibited Noxious Weed in 2015 and listed it as a Noxious Weed Seed in 2016 by emergency order. A genetic test to identify Palmer amaranth was simultaneously developed by multiple labs providing a tool to limit its spread as a contaminant in seed. Seed companies adopted genetic testing methods for labeling seed for sale reducing introductions via the seed pathway. Additionally, MDA determined that manure spread on crop fields from contaminated screenings fed to livestock resulted in new infestations. Limiting spread via these and other potential pathways was critical to successfully reducing the impact of Palmer amaranth. MDA, University of Minnesota (UMN) Extension, Conservation Corps Minnesota and Iowa (CCMI), farmers, and other partners are working to eradicate these infestations before they can spread. In 2016, 35 sites were sown with Palmer amaranth contaminated seed mixes. Palmer amaranth was found at eight (23%) of these sites. Management with intensive scouting, torching, prescribed burning, and herbicide application was implemented in 2016 and 2017. By 2018, no Palmer amaranth was found at any of these sites. Similar success to newer infestations in 2018, 2019, and 2020 was achieved using the same methods. MDA recorded management activities and documented a comprehensive timeline of Palmer amaranth in Minnesota. This timeline provides a story of success and challenges in combating and eradicating Palmer amaranth.
LITERA TURE REVIEW Plant Description and Characteristics Purple loosestrife, Lythrum salicaria L. (Myrtiflorae: Lythraceae), is a herbaceous European wetland perennial, that was introduced to northeastern North America in the early 1800's (Malecki et al' 1993, Thompson et aI. 1987). Purple loosestrife occurs throughout Europe from the 65th parallel south to the Mediterranean basin in North Africa (Blossey 1995b, Thompson et al. 1987). Outside of Europe, its native range includes Japan, northeastern China, southeastern Asia, and India (Thompson et al' 1987). Mature plants consist of a perennial rootstock producing 20-30 annual stems. The laterally branching rootstock serves as a storage organ providing resources for growth in the early spring and regrowth for cut or damaged stems (Malecki et al. 1993, Edwards et aI. 1995, Notzold et aI. 1998). Each stem produces several simple, opposite/decussate (sometimes whorled in threes), lanceolate leaves that are sessile (attached directly to the stem). Additionally, stems produce inflorescences (15-30 cm long) with individual flowers that are reddish-purple in color, rotate, and usually contain 12 stamens. Purple loosestrife reproduces sexually and does not produce rhizomes (Thompson et al. 1987, Hight and Drea 1991). Flowers are self-incompatible and insect pollinated by bumble bees (Apidae), honey bees (Apidae), syrphid flies (Syrphidae), Lepidopterans, and small halictid bees (Halictidae)
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