Browsing by Author "Beam, Shawn C."
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- Harvest weed seed control of Italian ryegrass [Lolium perenne L. ssp. multiflorum (Lam.) Husnot], common ragweed (Ambrosia artemisiifolia L.), and Palmer amaranth (Amaranthus palmeri S. Watson)Beam, Shawn C.; Mirsky, Steven B.; Cahoon, Charles W. Jr.; Haak, David C.; Flessner, Michael L. (2019-08)Herbicide resistance is a major problem in United States and global agriculture, driving farmers to consider other methods of weed control. One of these methods is harvest weed seed control (HWSC), which has been demonstrated to be effective in Australia. HWSC studies were conducted across Virginia in 2017 and 2018, targeting Italian ryegrass in continuous winter wheat as well as common ragweed and Palmer amaranth in continuous soybean. These studies assessed the impact of HWSC (via weed seed removal) on weed populations in the next year's crop compared with conventional harvest (weed seeds returned). HWSC reduced Italian ryegrass tillers compared with the conventional harvest at two locations in April (29% and 69%), but no difference was observed at a third location. At wheat harvest, HWSC at one location reduced Italian ryegrass seed heads (41 seed heads m(-2)) compared with conventional harvest (125 seed heads m(-2)). In soybean, before preplant herbicide applications and POST herbicide applications, HWSC reduced common ragweed densities by 22% and 26%, respectively, compared with the conventional harvest plots. By soybean harvest, no differences in common ragweed density, seed retention, or crop yield were observed, because of effectiveness of POST herbicides. No treatment differences were observed at any evaluation timing for Palmer amaranth, which is attributed to farmer weed management (i.e., effective herbicides) and low weed densities making any potential treatment differences difficult to detect. Across wheat and soybean, there were no differences observed in crop yield between treatments. Overall, HWSC was demonstrated to be a viable method to reduce Italian ryegrass and common ragweed populations.
- Seed-shattering phenology at soybean harvest of economically important weeds in multiple regions of the United States. Part 1: Broadleaf speciesSchwartz-Lazaro, Lauren M.; Shergill, Lovreet S.; Evans, Jeffrey A.; Bagavathiannan, Muthukumar V.; Beam, Shawn C.; Bish, Mandy D.; Bond, Jason A.; Bradley, Kevin W.; Curran, William S.; Davis, Adam S.; Everman, Wesley J.; Flessner, Michael L.; Haring, Steven C.; Jordan, Nicholas R.; Korres, Nicholas E.; Lindquist, John L.; Norsworthy, Jason K.; Sanders, Tameka L.; Steckel, Larry E.; VanGessel, Mark J.; Young, Blake; Mirsky, Steven B. (2021-01)Potential effectiveness of harvest weed seed control (HWSC) systems depends upon seed shatter of the target weed species at crop maturity, enabling its collection and processing at crop harvest. However, seed retention likely is influenced by agroecological and environmental factors. In 2016 and 2017, we assessed seed-shatter phenology in 13 economically important broadleaf weed species in soybean [Glycine max (L.) Merr.] from crop physiological maturity to 4 wk after physiological maturity at multiple sites spread across 14 states in the southern, northern, and mid-Atlantic United States. Greater proportions of seeds were retained by weeds in southern latitudes and shatter rate increased at northern latitudes. Amaranthus spp. seed shatter was low (0% to 2%), whereas shatter varied widely in common ragweed (Ambrosia artemisiifolia L.) (2% to 90%) over the weeks following soybean physiological maturity. Overall, the broadleaf species studied shattered less than 10% of their seeds by soybean harvest. Our results suggest that some of the broadleaf species with greater seed retention rates in the weeks following soybean physiological maturity may be good candidates for HWSC.
- Seed-shattering phenology at soybean harvest of economically important weeds in multiple regions of the United States. Part 2: Grass speciesSchwartz-Lazaro, Lauren M.; Shergill, Lovreet S.; Evans, Jeffrey A.; Bagavathiannan, Muthukumar V.; Beam, Shawn C.; Bish, Mandy D.; Bond, Jason A.; Bradley, Kevin W.; Curran, William S.; Davis, Adam S.; Everman, Wesley J.; Flessner, Michael L.; Haring, Steven C.; Jordan, Nicholas R.; Korres, Nicholas E.; Lindquist, John L.; Norsworthy, Jason K.; Sanders, Tameka L.; Steckel, Larry E.; VanGessel, Mark J.; Young, Blake; Mirsky, Steven B. (2021-01)Seed shatter is an important weediness trait on which the efficacy of harvest weed seed control (HWSC) depends. The level of seed shatter in a species is likely influenced by agroecological and environmental factors. In 2016 and 2017, we assessed seed shatter of eight economically important grass weed species in soybean [Glycine max (L.) Merr.] from crop physiological maturity to 4 wk after maturity at multiple sites spread across 11 states in the southern, northern, and mid-Atlantic United States. From soybean maturity to 4 wk after maturity, cumulative percent seed shatter was lowest in the southern U.S. regions and increased moving north through the states. At soybean maturity, the percent of seed shatter ranged from 1% to 70%. That range had shifted to 5% to 100% (mean: 42%) by 25 d after soybean maturity. There were considerable differences in seed-shatter onset and rate of progression between sites and years in some species that could impact their susceptibility to HWSC. Our results suggest that many summer annual grass species are likely not ideal candidates for HWSC, although HWSC could substantially reduce their seed output during certain years.