Bats Save Billions for Agriculture

August 20, 2016 02:52 AM

A hidden, nocturnal world of insect suppression 

A secret war is waged above farmland every night. Just after dusk, high-stakes aerial combat is fought atop the crop canopy. Nature’s air force arrives in waves over crop fields, sometimes flying in from 30 miles away. Bat colonies blanket the air with echo location clicks and dive toward insect prey at up to 60 mph. In games of hide-and-seek between bats and crop pests, the bats always win, and the victories are worth billions of dollars to U.S. agriculture.

Bats are an unheralded friend of farmers, providing consistent crop protection. How much do bats save agriculture in pesticide use? Globally, the tally might reach $53 billion per year, according to estimates from the University of Pretoria, U.S. Geological Survey (USGS), University of Tennessee and Boston University. 

A 2006 study proposed bats saved cotton growers $74 per acre in pesticide treatments across eight Texas counties. In 2013 and 2014, Southern Illinois University Carbondale graduate student Josiah Maines and his adviser, Justin Boyles, ran a field trial to show the relation between bats and corn protection. Funded by Bat Conservation International, Maines’ test targeted corn earworm in southern Illinois bottomland in Alexander County.

Maines built a net canopy system to prevent bats from accessing sections of corn at night. For two years, he slid the net in place from May to late September to cut off bat access to earworm moths. The results were astonishing.

He found a 50% reduction in earworm presence in control areas and a similar reduction in damage to corn ears. Not only did bats suppress earworm larvae damage to corn, they also hindered the presence of fungal species and toxic compounds. 

“Globally, we estimate bats save corn farmers over $1 billion annually in earworm control,” Maines says. “It’s an incredible amount when we’re only considering one pest and one crop. Bats are a vital economic species.”

Would farmers see greater crop protection with more bat habitat? Researchers don’t know how many bats fly over a single acre of farmland at night, and they are extremely difficult to count during the day. Bats hide in trees, caves, holes in the ground and buildings. Paul Cryan, a USGS research biologist at the Fort Collins Science Center, says of the 45 bat species in the U.S., 41 to 42 eat nothing but insects. Bats are small, 10 to 20 grams, but will eat half or all their body weight each night. 

However, pressing issues surround bat populations. White nose syndrome (WNS) is a fungal disease that’s spread halfway across the U.S. since 2006. “WNS has killed up to 6 million bats and continues moving,” Cryan says. “Farmers would see an immediate impact in insect suppression if overall bat populations were seriously reduced.”

Hat tip to the misunderstood bats of agriculture: phenomenal creatures patrolling farmland skies every night in the greatest show never seen. 

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Spell Check

Darshan Singh
Johnston, IA
8/23/2016 10:43 AM

  Interesting. Though bats by and large are insectivorous but one fails to comprehend as to how their exclusion from corn fields led to decreased fungal infection of crop. Moreover, is it not a possibility that canopy induced bat exclusion of corn would also result in reduced access to ear worm moths-thereby the resultant reduced egg layings and crop damage.


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