Invasive pigweed seeds found in most birdseed mix

Palmer amaranth, better known as pigweed

Researchers at the University of Missouri found out that commercial birdseed is giving Palmer amaranth, an invasive pigweed species, a sneaky ride into farms and gardens across the Midwest. Palmer amaranth is a frequent annoyance in the South, but was found "popping up in pollinator plots across the Midwest last year. Missouri scientists have also pointed to waterfowl contributing to the continued spread of the weed as the birds eat and subsequently poop the undigested and still viable pigweed seeds far away from the point of initial consumption," Pam Smith reports for The Progressive Farmer. The weed has spread to 39 of Missouri's 114 counties in recent years.

Mizzou weed expert Kevin Bradley says that the spread of the plant is usually blamed on contaminated livestock feed, bedding, or seeds clinging to machinery. His findings about the birdseed vector were presented at the university's recent Integrated Pest Management field day.

It's research worth noting, since some kinds of Palmer amaranth can resist several kinds of herbicides. The tiny seeds were present in almost all of the birdseed the researchers screened, but seed mixes that contain millet tended to have the most. One sample "contained nearly 8,000 pigweed seeds in a single pound bag. That's a lot of pigweed since birdseed often sells in 50 lb. bags," Smith reports. Seeds for other weeds were also common in the birdseed samples, including ragweed, velvetleaf, and morning glory.