Many may remember the 2015 growing season as the one in which the weeds took over in many Western Illinois soybean (and some corn) fields. Abnormally wet weather led to saturated soils that were impassible for long periods of time before post-emergence herbicides were applied. Weeds were extra thick in those fields that relied on a post-emergence-only weed management plan. Whatever the factors responsible for the thick weeds in 2015, many of those 2015 weeds produced seed. This seed was added to the field's weed seed bank where many remain to cause headaches in 2016 and beyond.
Most people have already devised their weed management plan for 2016, and many have made at least one tillage and/or herbicide pass across the field. The figure above illustrates one of the problem weeds that has been observed in Western Illinois this spring. This is a field in which the winter annual weed, henbit, went to flower and will soon set seed. From both a weed management standpoint, in which additions to the weed seed bank are unwanted, and from a planting logistics perspective, in which one wishes to not get weeds wrapped around the trash-rippers during planting, this photo does not illustrate an ideal situation. Both winter- and summer annual weed species can also directly compete with emerging crop seedlings for resources. Timely weed management is essential to both reduce competition and protect yield potential.
One useful resource to help in devising (or tweaking) an integrated weed management plan is the 2016 Ohio, Indiana and Illinois Weed Control Guide. According to University of Illinois weed scientist Dr. Aaron Hager this resource,
"contains 224 pages of weed management information, including weed response ratings for corn and soybean herbicides. Information and recommendations for managing weeds in small grains and forages is included, along with more specific information about and control recommendations for several problem weed species."
Additional resources that can help in weed management plans are: