With approval of dicamba resistant soybeans and now the products to spray on them, we need to plan to avoid the problems we had develop with excessive use of glyphosate as we move toward higher use of dicamba products.
The United Soybean Board has developed some very nice materials to fight resistant weeds. It involves using broad-spectrum pre-emergent herbicides as the basis for your weed control program. Mark Loux our Extension Weed Specialist supplemented and printed these packets for Ohio — they have been very popular at our pesticide re-certification training programs this winter. The campaign to manage resistant weeds is called “Take Action” against herbicide resistant weeds. The website to get more information is http://takeactiononweeds.com. I especially like the Site of Action chart: http://takeactiononweeds.com/understanding-herbicides/site-of-action-lookup/.
“There are no new herbicides” is not quite a true statement, as there are many new names, but it is the active ingredient that is important, the rest is about marketing of a brand name. So the site of action chart will help determine the active ingredient in a commercial product. One product now widely recommended to control ragweeds and pigweed species has the active ingredient fomesafen. Checking the chart I see this is a PPO, a cell membrane disrupter and in the SOA 14. Along with Flexstar, there are over 40 other products that have the same site of action. Do you know how to avoid overlap? Check the chart.