By MARK BUTZOW

Indiana correspondent

WEST LAFAYETTE, Ind. — Nobody likes weeds in their fields; they use up precious nutrients and moisture. So controlling them is a large part of farmers’ challenge each year.

As new threats emerge – and resistance grows to old dangers – industry and government have to adapt. Most states have laws on the books to help control invasive plants and noxious weeds that can reduce crop yields and cause harm to neighboring fields.

Ohio has 31 plants on its prohibited noxious weeds list and 38 on its invasive plant species list (some plants are on both). In Michigan, 14 species are labeled “prohibited” and another six are designated as “restricted.” The state also has separate prohibited and restricted lists controlling the seeds of 19 and 22 plants, respectively.

Illinois has nine species on its noxious weeds list, and Indiana’s state legislature added eight plants to its detrimental plants list this spring – bringing the tally to 13 varieties – while the Office of Indiana State Chemist (OISC) says a new rule is in the works to address the sale of seeds.

The plants added in Indiana include common waterhemp, tall waterhemp, marestail, palmer amaranth, poison hemlock, Powell amaranth, rough pigweed, and smooth pigweed. OISC Seed Administrator Don Robison said it’s necessary to revise the list now and then because threats keep changing.

“Waterhemp and palmer amaranth were hardly an issue 10 years ago; now they’re the two biggest problems in the state,” he explained.

Another weed gaining ground is rough pigweed, and Robison said Canada thistle is getting an especially good start this year because of the wet spring.

It’s the responsibility of a landowner – whether the land is a farm field, ditch bank, or open land – to at least keep prohibited and restricted plants from spreading.

“Some landowners are of a mind, ‘Why are you sticking your nose in my business?’ and some probably welcome the help because they’ve been trying to control weeds and are losing ground,” Robison noted.

Some states give county and township governments the enforcement powers, while others authorize their agriculture departments to eradicate out-of-control weeds. In most cases, the rules stipulate that landowners can be sent the bill. That has caused some resistance, but Robison said Canada thistle helps make clear the need for such laws.

“Canada thistle grows around the edge of fields,” he explained. “Its flower turns into almost a dandelion-type thing” with seeds eventually carried away by the wind. “Neighbors were not happy with neighbors.”

Robison is actually more involved with Indiana’s other effort to control weeds, the one involving seeds. When farmers buy seed for small grains or cover crops, there is an unwritten contract that they’re buying clean crop seed devoid of the seed of unwanted weeds.

One part of Indiana’s seed list includes “prohibited” species – “There can’t even be one noxious seed in there” – and the other part of the list are “restricted” species, which allows seed for sale to have a maximum of 0.25 percent of weed seed included.

Regulating seeds has been problematic for Indiana. There are several variants of the weed species called amaranth, and their seeds all look the same. Palmer has emerged as a serious threat, but other variants of amaranth are somewhat easy to control and are, therefore, permissible in small amounts in seed for sale.

State Chemist and Seed Commissioner Robert Waltz, with the input of Purdue University agriculture experts, wanted to move amaranth – all varieties – from the restricted seed list to the prohibited seed list. That didn’t go over well.

“Boy, was there pushback from industry,” Robison recalled. Banning all amaranth seeds would have made Indiana’s proposed rule the toughest in the nation, he added. Regulators have continued the rulemaking process and hope to have changes approved later this year.

The biggest challenge for farmers may be the resistance, not the regulators. Robison said weeds considered “prohibited” are on those lists because they are “terrible to control because of their resistance to chemicals” – a problem that may get worse.

“Roundup (glyphosate herbicide) made everything easy. With one chemical you could spray one thing to handle many problems. Now there is a resistance problem,” Robison said. Especially with waterhemp, he said there are fewer things you can spray to control it – and there is more of it.

“A whole generation grew up on Roundup, and now not having that one product” will be a big adjustment for farmers, he pointed out.