STARKE COUNTY — The cool and crisp smell of mint is heavy in the air here at this Northern Indiana farm.
Farmer Larry Wappel grows peppermint on 120 acres in San Pierre, Ind., a rural community about 55 miles north of Lafayette.
This farm is where WRTV accompanied Purdue University entomologist Elizabeth Long as she searched for an invasive insect that's killing these fields.
“The main work that we're doing in the mint fields is helping these mint farmers identify strategies to monitor and manage this invasive white grub,” Long said.
The grub is the immature stage of the Asiatic garden beetle, a pest that attacks a host of plants, including vegetables, grasses and ornamentals.
“It's become more and more of a problem in the mint fields where the grubs actually feed on the roots of the mint plants,” Long said.
The grubs are voracious eaters. They dine on the fine hair-like roots of the mint plants, striping the plants of their ability to draw nutrients from the soil.
It has been devastating to Wappel’s farm.
“We had fields that weren't making it through the winter, or would really struggle in the spring,” Wappel said. “And we had a hard time figuring out what's going on because all the damage happens underground.”
Mint is a small but important crop for our state. Indiana is the nation’s third largest producer of spearmint oil and fourth largest producer of peppermint oil, Long said.
With the plants dying off, Wappel and other Indiana mint farmers reached out to Purdue for help.
Long and her grad students have been studying these fields since 2020.
Researchers hope to kill these bugs without using pesticides, so they are turning to nematodes, microscopic worms designed by Mother Nature to attack and destroy grubs.
“It's a round worm that attacks only insects which is awesome because there's no non-target effects on us or other organisms besides bugs,” Long said.
Long applied these microscopic nematodes to part of this field and she’s studying how effective they are killing the grubs. She expects to have enough data to publish scientific results this fall.
"For now we're just excited to see if in the plots that we treated, are the nematodes still active? Are they effective? Can they still kill insects?" Long said. "And we're seeing that they can. So, that's really freaking exciting!"
The efforts are working, Wappel said.
"As you can see the field's pretty," Wappel said. "It's been a lot of work and it's fascinating.
"The grubs are my arch enemy, but I also respect them because they're resilient."
Contact WRTV reporter Vic Ryckaert at victor.ryckaert@wrtv.com or on X/Twitter: @vicryc.
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