Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/10/2009
Publication Date: 1/5/2010
Citation: Williams, M.M. 2010. Biological Significance of Low Weed Population Densities on Sweet Corn. Agronomy Journal. 102:464-468. Interpretive Summary: Controlling every weed in every field is not practical. While applying weed management tactics to fields with moderate or heavy infestations is critical to avoiding serious crop losses, decisions to control lightly infested fields depends on the impact of the weed on the crop. This research quantified how low population densities of giant ragweed affected sweet corn. A critical finding was that low levels of weed interference resulted in only subtle delays in crop development, but resulted in serious decline in traits important to the consumer and processor. The impact of this work is from providing information critical to decision making on weed control in sweet corn. Those who develop crop management recommendations (e.g. consultants and extension personnel) can use these results, along with site-specific information, to determine the economic outcome of applying weed management to lightly infested sweet corn fields.
Technical Abstract: Some weed plants escape current weed management systems in nearly all sweet corn (Zea mays L.) fields. Decisions to target escaped weeds, and justify the added expense, require knowledge of the biological significance of low weed population densities on the crop. The objectives were to 1) quantify giant ragweed (Ambrosia trifida L.) area of influence (AOI) on sweet corn and 2) investigate potential links among giant ragweed AOI and crop growth, development, and yield traits. All measured crop traits were influenced by giant ragweed AOI, including plant height near silk emergence, thermal time to silk emergence, green ear mass, husked ear mass, filled ear length, ear width at midpoint, and kernel moisture. Proportion of silked plants declined for sweet corn within 160 cm of giant ragweed, with less than one-half of the crop plants producing a marketable ear within 42 cm of giant ragweed. Weed interference harmed ear traits most when crop development was delayed, as evidenced by path analysis of giant ragweed’s direct and indirect effects on yield traits. Even the lowest population density of giant ragweed can be costly with yield loss estimates ranging from $0.86 to $8.75 per weed plant, depending on crop market type.