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Midwest Flooding Leads to Bumper Crop of Weeds

The 2008 floods were devastating to the Midwest (with an estimated $3 billion loss of crops in Iowa alone). A major issue for agriculture was the long-term unfavorable weather throughout the spring, which created problems for crop planting, crop growth and management decisions. Weeds had no problem with the adverse weather conditions and likely caused more loss of potential crop yield than ever before, because of difficulties in making timely herbicide applications. Dr. Michael Owen notes that flooded fields in river bottoms and “wet holes” within fields throughout Iowa were either replanted late or were too wet for any replant options. As a result, these areas had significant weed growth and are contributing prodigious numbers of seeds to the weed “seedbank” in the soil. Farmers will need to be prepared to manage the higher densities of weeds that are expected next year.

In neighboring Illinois, corn and soybean growers were also challenged by the extremely wet spring and subsequent flooding. Dr. Aaron Hager reports that excessive rain also caused many Illinois corn fields to be replanted, some more than once. Flooded areas in Illinois that remained too wet for replanting have also become havens for weed growth.

Farmers faced unusual challenges in these and other midwestern states. When having to reseed a corn crop, farmers would usually apply the herbicide glyphosate* to eliminate remaining corn plants but, with more farmers planting glyphosate-resistant corn, different options were needed. In other cases, farmers would have liked to replant soybeans, which can be a shorter season crop. However, prior applications of herbicides or heavy nitrogen inputs limited that option, causing some farmers to replant corn well into late June, two months past the optimum date.

Proper timing of herbicide application was perhaps the most frequently encountered challenge caused by excessive and unrelenting rain. As a result, inconsistent and incomplete weed control will likely contribute to reduced crop yields and ample restocking of the weed “seedbank”. In addition, cool temperatures coupled with excess moisture contributed to a higher frequency of corn injury following herbicide applications than is common in most years.

*Some common products which contain glyphosate or a glyphosate solution include Roundup®, Touchdown®, Buccaneer®, and Durango®. Always read and follow the directions for use on the product label.

Roundup® is a trademark of Monsanto Company. Touchdown® is a trademark of Syngenta Group Company. Buccaneer® is a trademark of TENKOZ, Inc. Durango® is a trademark of Dow AgroSciences LLC.

About the Weed Science Society of America:
The Weed Science Society of America, a nonprofit professional society, was founded in 1956 to encourage and promote the development of knowledge concerning weeds and their impact on the environment. The Weed Science Society of America promotes research, education and extension outreach activities related to weeds, provides science-based information to the public and policy makers, and fosters awareness of weeds and their impacts on managed and natural ecosystems. For more information, visit http://www.wssa.net.