California’s walnuts are in danger, and it’s not just from the ongoing drought. A moth larvae that burrows into the trees’ fruit and eats developing nuts threatens up to 10 percent of walnut farmers’ crop every year, reports Susan Moran for Ensia. Pesticides can keep the pest at bay, but come with an ecological cost. But Moran reports that a better way may be to rely on one of the best bug hunters around: insectivorous bats:
[B]ats are known to have huge value in controlling crop pests generally: The economic return on their nighttime insect-eating services has been estimated at about US$23 billion per year for the U.S. alone, and research has shown that bats can help control pests in cotton fields and pecan groves in Texas, cornfields in the Midwest and rice fields in Thailand.
But exactly how well can bats work as flying, sonar-equipped bug protection? Moran follows the work of researcher Katherine Ingram, who is working to quantify the benefits of using bats to keep moths away from walnut trees. "[I]f we can go beyond anecdotes and say for sure what the ecological and economic [benefit] is, that’ll go a long way," Ingram tells Moran.
Already scientists know that setting up a bat house can help beat back the moth invaders, but Ingram wants to figure out the financial benefit of bats to help convince other growers that putting up such a structure is worth it, and can offset the cost of insecticides that can run up to at least $160 per acre.
The research may also persuade people that bats are worth conserving. While the fungus that has been killing bats in the Eastern U.S. hasn’t appeared in California yet, bats may prove useful for other crops as well.