I have been asked by a few people about the differences in metolachlor (the active ingredient in Dual) products. The “old” Dual in the early 1990s was two isomers of metolachlor, R and S isomers. The Dual II included a safener to improve crop safety (improves safety to corn, not to broadleaf crops; hence Dual for broadleaf crops and Dual II for corn).
In mid-1990s Syngenta came out with a version of “Dual” that contain only the s-isomer (the herbicidal active isomer) and called it Dual Magnum; and the version with the safener was called Dual II Magnum. Because the Magnum formulation only contained the active isomer, the rates changed between the Dual and Dual Magnum formulations.
Now that there are a lot of generic versions out there it has become confusing. Some contain both isomers, others contain only the s-isomer and are usually designated as s-metolachlor. Some may contain the safener and others do not. It is not always apparent what formulation is used or if a product has a safener. Often you may have to dig deep into the label or the company’s technical material to find this information. With the cool spring we have been having, early planted corn should be treated with a formulation that contains the safener.
Finally, Syngenta has worked with a number of states to obtain labels for specialty crops and additional uses. Most generic products do not have all the uses that the “Dual” labels have. Be sure to read the labels and be sure the formulations are labeled for the intended use. Do not take it at face value that all the generic metolachlor products are “the same as Dual”.