Pigweed (Palmer Amaranth) has been a frequent topic of conversation among farmers and food plot guys in the last several years. Pigweed has been causing severe problems because of its rapid growth and in many parts of the county, resistance to glyphosate which leads to problems in glyphosate resistant crops that are being grown. In warm season food plots, whether it is a spring planted perennial or annual blend, pigweed can very quickly become a problem and overtake the plot. When left to mature and go to seed, pigweed grows a substantial amount of seeds that can continue to cause problems for years down the road. They key to killing and controlling pigweed is early identification and proper herbicide application. Imazamox is a great broadleaf control herbicide with chemistry that has excellent results and residual control on pigweed and other broadleaf weeds. Imazamox (brand names Weed Reaper or Raptor) can be sprayed over legumes including clover, alfalfa, beans, peas, and lablab.
Ideally, broadleaf weeds should be less than 6 inches in height for the best kill. My first experience in testing imazamox was on a severe infestation of pigweed on over 10 acres of spring planted Lablab a few years ago. The Lablab was less than two weeks out of the ground when I noticed a solid carpet of pigweed beginning to emerge. Left untreated, the Lablab would have easily been outgrown by the rapid growth of pigweed and my summer crops would have been non-existent. I tested BioLogic Weed Reaper (imazamox- active ingredient) at a rate of 4oz per acre with AMS (ammonium sulfate) and a surfactant as a tank additive. I was pleasantly surprised on my return trip to the fields to find a 95% + kill on all broadleaf weeds including the solid carpet of pigweed that was completely nuked. The only areas I could find with less than ideal results were due to inconsistent spots in the spray pattern and not failure on the herbicide. These were all at the end of my turn rows where I didn’t get quite enough overlap. If you have trouble growing warm season plots because of broadleaf weeds, imazamox may be your answer. Nobody likes to spend the money and effort of planting only to have it ruined by problematic weeds.