Brief Summary of Minutes of Annual Meeting

Short-term outcomes: The immediate benefits of the NC1191 weed phenology project will be to improve our ability to predict the timing of weed seedling emergence and seed production. This will aid farmers in developing cost-effective management plans for timing weed control efforts on their farm. Outputs: We will generate regional-scale data on the phenology of summer and winter annual weeds of the north central region. These data will be used to update and improve models of weed seedling emergence. Activities: Phenology of common lambsquarters (Chenopodium album L.), field pennycress (Thlaspi arvense L.) and horseweed (Conyza canadensis L.), and velvetleaf (Abutilon theophrasti L.) was recorded from a common garden experiments in the home locations (KS, MI, NE, ND, MN, OR, SD) of each participant during late summer/fall of 2012 and spring of 2013. For each weed species, seeds from common and local accessions were planted. Experimental units consisted of 1 m2 quadrats with two types of measurements taken within: seedling emergence, and monitoring of flowering and seed maturation within the quadrat as a whole. Each 1 m2 quadrat contained four evenly spaced rows (0.25 m between rows) of a given experimental species seeded at 30 seeds row-1.(populations will ultimately be thinned to 2-4 plants per row, for a total of 12 plants per quadrat; see below). Phenology measurements included seedling emergence over time, floral initiation (onset of anthesis), and species-specific measures of seed maturation. Weed seedling emergence was recorded non-destructively twice a week until there were at least 2-4 plants per row. Seedlings were thinned to leave 2-4 plants per row, to achieve a total quadrat population of 12 plants. Floral initiation and seed maturation for each marked individual in each plot was recorded. The group plans to collect similar phenology for one additional year (2014), at which time we will have a large comprehensive dataset from which to test the current parameterization of Hopkins Bioclimatic Law (HBL). By improving HBL, we will be able to develop more accurate predictions of weed phenology in support of weed management. Milestones: We will collect four years of weed phenology data that are required to improve modeling approaches for more accurate weed phenology predictions. This year we collected the third of four planned datasets documenting the phenological responses of four weed species at the home locations of each participant. Data were summarized by each participant and presented at the annual meeting to inform the group of progress on the project and to note any pitfalls or concerns about future data collection.

Sharon A. Clay, Adam Davis, Anita Dille, John Lindquist, A. Ramirez, Christy Sprague, Graig Reicks, and Frank Forcella (2013) Common Sunflower Seedling Emergence across the U.S. Midwest. Weed Science In-Press. Adam S. Davis, Sharon Clay, John Cardina, Anita Dille, Frank Forcella, John Lindquist, and Christy Sprague (2013) Seed Burial Physical Environment Explains Departures from Regional Hydrothermal Model of Giant Ragweed (Ambrosia trifida) Seedling Emergence in U.S. Midwest. Weed Science: July-September 2013, Vol. 61, No. 3, pp. 415-421.