Biological Significance of Low Weed Population Densities on Sweet Corn

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 (i) quantify giant ragweed (Ambrosia trifida L.) area of influence (AOI) on sweet corn, and (ii) investigate potential links among giant ragweed AOI and crop growth, development, and yield attributes. All measured crop attributes were influenced by giant ragweed AOI, including plant height near silk emergence (HT), thermal time to silk emergence, green ear mass (GMASS), husked ear mass (HMASS), filled ear length (LENGTH), ear width at midpoint (WIDTH), and kernel moisture (MOIST). 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 attributes most when crop development was delayed, as evidenced by path analysis of giant ragweed's direct and indirect associations with yield attributes. 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.