Last fall, after the drought had killed off most of the competition, a certain weed took advantage of the opportunity to germinate and flourish. And now, the thistle is hurting productivity on many Missouri farms.
Tim Schnakenberg can tell you pretty much anything you need to know about the soil as it relates to Missouri crops. His phone at the MU Extension office in Lawrence County has been ringing off the hook with farmers complaining about the pesky, invasive weed. It has several forms—musk and bull thistles are common here.
“It’s mainly a problem in pastures and hayfields, where we’re trying to produce feed for cattle. You know, if cattle come upon a thistle, they’ll make a beeline around it,” Schnakenberg says.
That’s because it has serious thorns. And so, that acreage ends up being unusable—cows can’t graze there, and crops can’t grow. And many farmers have had the unexpected cost of trying to get rid of the thistles, affecting productivity and a farmer’s bottom line. Schnakenberg says there are really three options for people battling thistles.
“Some will go out, and they’ll dig them—they’ll take a shovel or a pick-axe or something like that, and try to dig them out. And [they’ll] try to get them as deep as they can, and get their roots. But with the sheer volume we’ve had in some fields, that’s just not always practical,” Schnakenberg said.
Others have tried mowing over them. But for mowing to be effective, farmers have to time it perfectly – they have to mow just before the purple seed head opens up, and they’ll have to mow again several times in the following weeks.
But the best way to control the thistle is also the last resort — and it’s what Don Proffitt is doing at his beef cattle farm in Pottersville, Missouri.
He opens the chain on the metal gate leading to the field he “broadcast sprayed”— that means he sprayed herbicide on the entire field, instead of just a few select spots, because the thistle was so widespread.
“This is the first year that we’ve really broadcast sprayed thistles. And I’m really, really pleased with the result so far,” Proffitt said.
As Proffitt’s red cattle surround our truck, we drive to a corner of the field where a couple of thistles have survived. He says the weed killer itself isn’t expensive, but time and labor can be. He hires a farm hand to help him in the fields.
“And he’s probably spent 80 or 90 hours spraying, just spot spraying. But I just can’t stand to leave them, especially when they get white and start blowing [seeds],” Proffitt said.
About 30 years ago, the USDA and the University of Missouri released weevils—tiny, white worms—that went to work attacking the flower-head of the thistle. And they’re now in every county, says Schnakenberg.
“I shudder to think about if we didn’t have the weevils, just how many more thistles we would have had,” Schnakenberg said.
The thistle is also causing some drama between neighbors, according to Tim Schnakenberg. That’s because while some farmers are diligently trying to fight off the thistle in their own fields, others are letting them go, which allows seeds to float through the air and germinate in a neighbor’s land.
Missouri law (section 263.190 of the Revised Statutes of Missouri)says landowners must control all thistles each year to prevent them from going to seed.
This story originally aired as part of Under the Microscope, a weekly program about science, health, and technology in mid-Missouri.