Bats worth a billion in bug control

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Capital News Service
LANSING — Bats get a bad rap, but a new study proves that they’re hard workers, and that the work they do is worth more than $1 billion to farmers.
The study shows that bats play a vital role in keeping in check corn earworm moths and larvae that destroy corn, cotton, tomato and other important crops.


Corn earworm moth captured in pheromone trap. Credit: Josiah Maine

It’s no news to farmers that bats are important pest regulators. But without knowing just how much bats contribute, it’s hard for farmers to confidently decide to reduce their pesticide use, said Christie Bahlai, a research associate at Michigan State University’s Department of Entomology.

“Farmers are stewards of their lands and know better than anyone that many pesticides can be dangerous and cause adverse effects,” said Bahlai, “They don’t always know if the natural enemies will be sufficient to keep pest populations in check.”
“Farmers in general always look for alternatives to control pests other than chemistry,” said Jim Zook, executive director of the Corn Marketing Program of Michigan and the Michigan Corn Growers Association.
The top five corn-producing counties in Michigan are Huron, Saginaw, Sanilac, Lenawee and St. Joseph, according to the Corn Marketing Program of Michigan.
The study’s authors say they hope their findings lead to reduced use of pesticides that can harm the environment and human health.
“Bats may reduce use of insecticides by suppressing pest populations below the threshold where insecticides are necessary,” said Josiah Maine, a graduate student at Southern Illinois University at Carbondale and co-author of the study.
And there are other bat benefits for farms, experts say.
“By reducing populations of crop pests, bats also reduce growth of pest-associated fungus on corn and the toxic compounds produced by the fungus,” Maine said.
Identifying the species that bats target and how many pests that bats eliminate helps researchers work with farmers to balance optimal crop yield and ecological integrity.
For instance, the study found 59 percent more corn earworm larvae on corn protected from bats compared to unprotected control areas. That number could help a researcher like Bahlai determine the minimum amount of pesticide that needs to be used on a field where bats feast.
In a previous project, Bahlai helped farmers manage sprays for the soybean aphid by developing a “dynamic action threshold.” The threshold factored in how many “natural enemies”—like bats, beneficial insects and birds—were in the farmers’ fields. That assisted farmers in determining when an infestation was serious enough to begin using more pesticides.
Her work lowered the application of pesticides on Ontario soybean fields by two-thirds.
Studies like Maine’s and collaborations with researchers like Bahlai can lead to changes in how farmers operate.
Bahlai said, “Changing practices can be difficult and expensive, and sometimes people don’t know where to start.”
Agricultural extension educators are a great help, she said. “They’re trained to provide information and support to help farms make transitions to the best possible practices.”
And a number like $1 billion in savings perks up the ears of policymakers, landowners and others with a financial interest in agriculture, helping them understand the value of protecting bat populations.
The study appeared in the Proceedings of the National Academy Sciences.
Marie Orttenburger writes for Great Lakes Echo
“Bats initiate vital agroecological interactions in corn”:

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