As Halloween Approaches: the Value of Bats to Crop Production
Posted: September 29, 2015
I happen to be a strong believer in the value of diversity for crop production, and talk about this issue regularly at farmer events. Research has clearly demonstrated that cropping areas that have higher levels of plant species diversity and more complex crop rotations, including cover crops, tend to have fewer insect pest problems. I therefore try to encourage farmers to increase crop or rotational diversity wherever possible to gain from the accompanying lower pest pressure. And keep in mind that maintaining higher levels of plant species diversity can be as simple as not removing hedgerows, woodlots, or other non-crop areas.
Complementing this perspective is some valuable recent research on bats from researchers at Southern Illinois University in Carbondale, IL. An unprecedented two-year corn experiment in corn fields revealed that bats save about $1 billion in crop damage per year. The field work associated with this research involved excluding bats from six research plots (65 × 65 ft) while allowing them access to six others. To exclude bats, researchers constructed above fields a system of steel cables that suspended netting (23 ft tall), which was moved to the side during the day, but was in place during evening. These cages were in place about three months of each of the 2013 and 2014 field seasons. This experiment revealed that when bats did not have access to the airspace above corn fields, corn earworm populations were about 60% higher and earworms damaged about 50% more kernels than plots that bats could not access. Further, as a result of corn earworm feeding, fungal infestations of corn ears were much higher where bats were excluded, so an absence of bats can indirectly exacerbate fungal infestations!
This research clearly indicates that having bats around benefits crop production. Thus, we need healthy bat populations to take advantage of the voracious appetite for moths, like corn earworm, European corn borer, armyworm, and others. Bats will roost during the summer in barns and trees, so keeping old drafty barns standing and leaving trees near fields should provide some benefits. Or consider contributing to the abundance of summer roosts by putting out bat houses!
For more information on bats in general and how to build a bat house, see this Penn State Extension publication. Lastly, this research also emphasizes reasons to be concerned about white nose syndrome, which is threatening local bat populations. I encourage you to educate yourselves about bats so we can do what we can to support their populations. They are our allies in pest control!