DE, MD Fields with Palmer Amaranth Resistant to Both Glyphosate and ALS-Inhibiting Herbicides

Last fall we collected seed from Palmer amaranth plants in Delaware and Wicomico County, Maryland and tested them for resistant to both glyphosate or ALS-inhibiting herbicides (Group 2). A few of the samples tested positive for resistance to both glyphosate AND ALS-herbicide. We used Pursuit in the initial trials, but past experience indicates that these biotypes are resistant to many other herbicides in this family. See the table below for list of common ALS herbicides in the region.

The following products contain only ALS-inhibiting herbicides, or the other active ingredients in the mixture are not effective for ALS-resistant Palmer amaranth control:

While the following herbicides contain ALS-inhibiting herbicides, they also contain at least one other active ingredient that is effective for Palmer amaranth control:

It should be mentioned there are a number of other effective herbicides to control Palmer amaranth biotypes that are resistant to both glyphosate and ALS herbicides. These herbicides include PPO herbicides (see the following article); HPPD herbicides such as Callisto, Balance, Impact, Armezon, and Laudis; PGR herbicides such as dicamba or 2,4-D; triazines such as atrazine and metribuzin; many of the Group 15 herbicides such as Dual, acetochlor, and pyrozasulfone (Zidua, Anthem, Fierce); and Liberty with Liberty Link soybeans.