Natural insect repellant for your clients

Since 1996, Dave Minnich of The Greener Side, Kutztown, Pa., has provided ecological and environmentally-conscious design, including the use of bat boxes. As primary predators of night-flying insects, bats are vital in balancing nature, and there’s never been a more important time to help these mystifying mammals. Adding a bat house as part of a landscape design can provide natural insect control for homeowners.

The U.S. Forest Service has been closing thousands of caves and former mines in national forests in 33 states in an effort to control a fungus that’s killed an estimated half-million bats in hibernacula, particularly in the Northeast. The puzzling affliction—dubbed “white-nose syndrome” (WNS) because of a halo of white fungus that develops around their faces—was first reported in New York, Vermont, Massachusetts and Connecticut. In February 2009, WNS sites were confirmed in New Jersey, Pennsylvania, central West Virginia and southern Virginia. Scientists say the loss of 500,000 bats means 2.4 million pounds of bugs aren’t eaten in a year.

Photos Courtesy of Rob Mies, Organization for Bat Conservation.
Bats in bat house. Installing bat houses at Cranbrook in Bloomfield Hills, Mich.

“One mine in northern New Jersey that contained about 30,000 little brown bats two winters ago had only 650 bats this winter,” says John Chenger, of Bat Conservation and Management, Inc. in Carlisle, Pa.

Because of the fungus, and because many bats are roosting in substandard areas due to human disturbance or habitat loss, providing ideally constructed and located artificial roosts has never been more critical.

Chenger began popularizing bat houses in the early 1980s. However, despite countless site selections and installations, even he suggests there are differing opinions about their success. It’s difficult to attract bats to areas where they don’t already live or in areas with ideal natural roosts.

In Pennsylvania, Cal Butchkoski, a wildlife biologist with the Pennsylvania Game Commission, built an 8-by-8-by-8-foot “bat condo” mounted 10 feet high in the summer of 1995. Requiring 280 man-hours and $4,000 of materials to built, it can fit 10,000 bats. The core of the building is 16 large clusters of .25-inch plywood used to create numerous .75-inch-wide roosting crevices. Half are triangular so bats can fit into the roof’s peak.

The structure roughly replicates conditions in a nearby abandoned church attic still occupied by some 20,000 bats. In 1994, the state’s Wild Resource Conservation Program bought the church for $5,600, then studied the attic’s size, design and temperatures to learn what bats want in a roost.

Chenger has scaled down the condo concept to a 4-square-foot mini condo. Built for less than $1,000, it can attract 2,500 bats. In April, Chenger installed one in a township park outside Hellertown, Pa., adjacent to a 19th century one-room schoolhouse on the National Register of Historic Places where bats had to be safely excluded.

Photo Courtesy of Jack Cahalan.
Newly erected mini bat condo at Lower Saucon Township’s Kingston Park in Pennsylvania.

It’s easy for an industrious landscape professional to make and market his own bat houses. The correct construction, installation and location are key to attracting bats. Use .5-inch, exterior-grade plywood for the roost baffles and .75-inch, exterior-grade plywood for the exterior front, back and sides. Don’t use pressure-treated wood, as bats don’t like the scent of chemicals. All pieces are screwed together and glued to prevent separation and air gaps.

The landing plate extends 4 to 6 inches beyond the bottom of the house, and like the roost-partitions, is screened or roughened to provide a firm gripping surface. The lower two-thirds of the house are vented, either with horizontal or vertical gaps. Crevice dimensions of .75 inch are ideal for most North American bat species.

Houses should be mounted at least 10 feet high, and in an open area exposed to seven-plus hours of direct sunlight that’s within .25 mile of a water source and 10 to 30 yards of cover, like a hedgerow, with abundant insect activity.

Data has shown that when three or more bat houses in various dark colors and with different sun exposure are installed in a group, occupancy is 80 percent. Single houses are only successful about half of the time, Chenger says.

In most climates, bat houses should be oriented to the east, southeast or south. On wooden or masonry buildings, bat houses should face south or east. However, in the warmest regions, north-facing houses do best. Those on poles should be mounted as a back-to-back pair with one box facing north and the other south. Avoid bright substrate, which reflects light up into the box, or anywhere near smoke. Bats also don’t like drafts and will vacate structurally unsound roosts.

The Audubon Certification program for golf courses advocates the use of bat houses. Saucon Valley County Club in Bethlehem, Pa., is certified, and incorporates bluebird boxes and other nature-attracting devices on its course.

Will Varner, of Wild Birds Unlimited (WBU) in Allentown, Pa., one of the company’s 300 franchised nature shops, sells 100 bat boxes a year, including to landscapers.

“A lot come in and say, ‘Who would want bats in their yard?’” says Varner, who partners with wife Pat in the business. “Then I explain how they catch thousands of mosquitoes a night, and the next thing you know they’re bringing a bat box to the cashier’s desk.”

Varners says, “They work, they really do. Then, you don’t have to use pesticides and bug killers. And, no more zapper lights. We don’t need candles, or to burn citronella. It’s fun just watching them fly, too. All of a sudden they’ll swarm out like they’re on a timer when it’s time to eat.”

To entice them, Varner suggests smearing banana on the outside front side where the bats enter. “The immature bats get in there, and the cycle starts,” he says.

Minnich agrees that bat boxes are the right thing for the environment and his clientele—and at a time when the bats need us the most.

The author is a widely-published writer and English teacher at Emmaus (Pa.) High School. For over 25 years, he’s written in nearly every journalistic genre and been published in 75-plus national and regional magazines, as well as dozens of daily and weekly alternative city newspapers.