Dual Use on Lima Beans for Delaware

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

Many folks are using about 1 pt of Dual Magnum (or equivalent product) at planting, which is a lower rate than we use in soybeans and corn. Higher rates are labeled with lima beans for our sandy soils (up to 1.3 pts) and while there maybe some leaf crinkling upon emergence it does not impact yield or delay maturity.

Kurt Vollmer has done a lot of work with Dual on lima beans over the past few years through funding by Delaware Department of Agriculture’s Specialty Crops Grant as a way of expanding the residual control from Dual Magnum. He researched the concept of “overlapping residuals” with additional Dual Magnum applied after the lima beans have emerged. He looked at all of the commercially grown baby lima varieties and found good crop safety with all of them. Syngenta asked for (and received) a state label for Delaware (24c) (its pending in Maryland) for a postemergence application. This will not control any weeds that have emerged, but will extend residual control of susceptible species such as grasses and pigweeds. The total amount of Dual Magnum cannot exceed 2 pt/A for the season (at planting plus after lima bean emergence).

Besides the rate limitation, other restrictions or comments include

  • applications only after the first trifoliate stage of the lima bean
  • applications can be made after cultivation, but at least 50 days before harvest
  • we have not looked at tankmixes with Dual Magnum to determine if there is an increase in injury
  • occasionally leaf crinkling may appear on the small leaves present at application, but later emerging leaves are not affected
  • rainfall or irrigation is needed to move the Dual Magnum into the root zone
  • labeling is for Dual Magnum formulation of s-metolachlor/metolachlor only