At a northern Iowa location, populations of 145, 203, 62, and 37 velvetleaf plants/m2 emerged in the four years following seed production by 0.4 velvetleaf plants/m2 growing in soybean. Annual velvetleaf densities in areas with no seed input averaged less than 6 plants/m2. At a central Iowa location, verticillium wilt reduced velvetleaf seed production, resulting in an average increase of 9 plants/m2 in the two years following seed production compared to the control treatment. This type of information is necessary to develop economic optimum thresholds, but the variability between locations demonstrates the difficulty in predicting crop and weed responses to management strategies implemented early in the growing season.
