Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 12, 2007
Publication Date: June 1, 2007
Citation: Williams, M., Boydston, R.A., Davis, A.S. 2007. Wild proso millet (Panicum miliaceum) suppressive ability among three sweet corn hybrids. Weed Science. 55:245-251. Interpretive Summary: Weeds cause serious losses in sweet corn yield and quality despite extensive use of herbicides. A non-chemical approach to reducing the negative affects of weeds in some agronomic crops is to take advantage of crop interference, either through breeding or cultural management. We found large variation among commercially available sweet corn hybrids in their ability to suppress wild proso millet, a common annual grass of the crop. In addition, we identified several canopy traits that were correlated with weed suppressive ability of the crop, including late season leaf area index and light interception. The impact is that we now know that not all hybrids suppress weeds the same, and with additional research, may be able to use this knowledge to improve weed management in sweet corn.
Technical Abstract: Due to known variation in canopy properties among sweet corn hybrids, weed suppressive ability (WSA), the crop’s ability to reduce weed fitness, may not be uniform among hybrids. This hypothesis was tested using a range of wild proso millet densities subjected to four canopy treatments (three hybrids + weedy monoculture) under irrigated conditions in Washington and primarily rainfed conditions in Illinois. Variation in hybrid suppression of wild proso millet was evaluated by comparing among canopy treatments the coefficients of regressions of weed growth and seed rain on wild proso millet seedling density. The same coefficients were used in a correlation analysis to identify associations between weed response and sweet corn canopy properties. Weed suppressive ability, as measured by wild proso millet shoot biomass and seed rain, varied among canopy treatments. Hybrid GH2547 was 25 to 31% more suppressive of wild proso millet than hybrid Spirit in Washington and 70 to 91% more suppressive in Illinois. Weed fitness was negatively correlated with leaf area index after crop anthesis (-0.48 to -0.63), intercepted photosynthetically active radiation at one of two harvest times (-0.51 to -0.56), and leaf area index at the 120 to 150 cm height (-0.51 to -0.55). Information on WSA may be useful in breeding programs; however, even near-term use of this knowledge offers modest but cumulative improvements to weed management systems in sweet corn.