The status of weed control across the state and the most effective herbicides for tackling weeds are outlined in a recently released Iowa State University Extension publication. Weed control and herbicide resistant weeds are among the topics being discussed this week at several sessions of ISU's annual Integrated Crop Management conference at Ames.
The "2016 Herbicide Guide for Iowa Corn and Soybean Production" was written by ISU Extension weed specialists Bob Hartzler and Mike Owen and is now available online at the Extension Store at store.extension.iastate.edu/.
Herbicide-resistant weed populations are slowly increasing
Hartzler and Owen note that the many weed issues from the past continue to plague Iowa farmers, particularly the weed waterhemp, in soybean fields. "There has not been a notable increase across the state in major weed management failures," according to Owen. "However, random surveys suggest that a high percentage of fields with weeds visible above the soybean canopy have evolved resistance to one or more herbicides." Owen and Hartzler conclude that herbicide-resistant weed populations are slowly increasing.
The two experts advise that now is the time for farmers to make adjustments to their weed management programs before weed densities become worse. Their suggestions include diversifying the types of herbicides you apply on your fields as well as paying attention to how and when herbicides are used.
Design an effective herbicide program, and manage resistance
The new 24-page ISU weed management guide provides industry updates and gives instructions on how to design resilient herbicide programs to manage herbicide resistance. The resilient herbicide programs rely on multiple herbicide groups to manage weeds, and the new publication details successful approaches. Non-herbicidal strategies also are included.
The publication also lists the effectiveness of different herbicides for controlling grass, broadleaf and perennial weeds in corn and soybeans, grazing and haying restrictions for herbicides used in grass pastures and the active ingredients in herbicide prepackage mixes. The publication contains four tables on herbicide sites of action (the specific proteins that herbicides inhibit in plants to kill them) and information about typical injury symptoms. "Herbicide programs that include several different sites of action are a key step in managing herbicide-resistant weeds," the authors wrote.