Tips for collecting weed seeds
Confirming herbicide resistance in weed populations is the first step of any resistance management program. This is determined by sending weed seeds to a local Extension office testing lab.
Erin Hill is a weed diagnostician at Michigan State University. She says weed seeds are usually collected in late summer-early fall. Know where the seeds are formed on the plant, and what they look like when they’re mature.
"You need to be looking in the correct place on the plant for usually a dark-colored, hard seed, and that depends on the plant. For example, does every Palmer Amaranth plant have seed? The answer is no, because for Palmer Amaranth there are male plants, and there are female plants," explains Hill. "So, you can’t just go pull five random plants, you actually have to look for the seed."
Hill says once you’ve collected the seeds from several plants, package them in something that’s breathable so mold doesn’t form on the seeds and compromise their viability.
"I usually advise people to pack them in a paper bag or an envelope, and then to double-bag that or also put it in a box so it’s not leaking seed. Because if you’re going to be mailing it, or transporting it and it is resistant, you don’t want to be leaving a trail of resistant seed with you," she says.
The seeds are grown and tested in a greenhouse, and it usually take a few months to get the results. But according to the Weed Science Society of America, nine out of 10 herbicide failures are due to factors other than resistance. They include weather conditions at the time of spraying, inappropriate weed size or life stage, improper sprayer calibration, and one plant shading another.