Bats as Part of a Sustainable Pest Management Approach to Controlling Moth Pests in Commercial Apple Production

Al-Mar Orchards is a 250 acre farm in central Michigan that has 100 acres of apples trees, woods, meadows, crop land and a creek containing slow moving water all-year round that cuts through the center of the property. The apple orchard is certified organic and the bordering lands do not receive any chemical treatments. The main income from the family operation comes from the retail and wholesale of organic apples and cider grown on the farm.

Coddling moth pests are difficult to control in organic orchards when these pests are high, Mating disruption, suffocating oils and spray able virus are close to 100% effective if one can keep the residential coddling moth population low. Cardboard banding of each tree and then burning the over-wintering pupas that ate in the cardboard helps, but this practice is very labor-intensive. Coddling moth adults are slow, poor flyers that take flight at dark and therefore are very vulnerable to bat predation. A high residential bat population should keep the coddling numbers low.

My farm, after researching bats preferred habitat, should be a perfect home for this coddling moth predator. Bat colonies prefer to take up residency near orchards and meadows that have diverse flauna and flora and are close to ponds or slow-moving bodies of water. Because my farm matches this description perfectly, I decided to design, build and erect a couple of large bat houses in this perfect setting.

After researching the best designs for a bat house, I settled on building a large, 4ft x4ft x 16” multi-chambered house with both nursery cells and bachelor cells. These two, 650 lb. projects were built entirely out of cedar, screws and glue. The houses were carefully designed and built so that there were several temperature possibilities within the same structure, using appropriate ventilation and eliminating drafts. This was a nice winter project that took several weeks to complete, working a couple of hours a day on the project. The challenge was erecting these “monster” houses 24 feet above the ground (the recommended height for bat houses if one wants to attract and maintain a colony of them). This was accomplished by fabricating the top half of the legs to the house, lifting them and the house up the 12 feet to the other set of legs, and then bolting them together. Choosing a no-wind morning, a good prayer, and three responsible friends, the two houses were erected without a single mishap, using my neighbor’s skidsteer with a fabricated lifting boom.

Three summers passed and no bats took up residency in my wonderful bat condos’ coddling moths ravaged my orchards and I wondered what could have possibly gone wrong. I talked to several bat experts and they all said that there is a real mystery behind what really works to attract bats. No one can figure out a perfect formula; only patience and time results in successful occupancy.

Finally, this summer, 2005, a few bats occupied one of the bat houses. The houses are designed to hold about 750 bats, so it make take a few years of colonization to build up their numbers and determine the impact of their predation on my coddling moth pests.

I would encourage every orchard owner to build and place a couple of bat houses around their farms, for biodiversity is the key to sustainability. The important lesson learned here is that it may take a long time to establish a bat colony that will aid in one’s pest control. Statistics from my research indicated that I should have had an 80% success rate the first year given the geography of my farm. And yet it took three years. This long-awaited successful residency establishment will eventually make it easier to establish more bat colonies in my area. This should surely aid in my insect pest control.