2008-08-30 / Top News

Island Takes New Steps To Curb Flies

By Diane Ivey

In the last two weeks of July and the first two weeks of August, Mackinac Island's fly population increases dramatically, and on an island where horses are a primary source of transportation, flies can quickly become a problem. The City of Mackinac Island is hoping a new fly predator program this year will improve the Island's overall fly control program.

Fly predators, which are tiny wasps that lay eggs in fly pupae, are just part of the Mackinac Island program, which, since the Island stopped spraying insecticides in 1978, also includes sanitation, manure composting, and the use of fly traps to control the pests.

But this year, Island officials have found a new distributor who is providing four species of wasps that will attack biting flies as well as house flies. The fly predators are in the pupal stage when received, and resemble a small, black rice kernel, allowing barn owners to sprinkle them around areas where flies propagate.

When hatched, the predator wasp locates the fly pupa and drills a hole through the shell with her egg depositor. As many as a dozen wasp eggs are deposited into the pupa, where they will feed off of the pest fly larva while developing into mature adults in 14 to 28 days.

The little wasps don't sting or bite and don't bother people or animals.

Between houseflies propagating in manure and biting flies that breed in decaying organic matter, keeping the fly population under control is a challenging battle, said Dr. Al Sibinic, who is the veterinarian for Mackinac Island Carriage Tours and maintains a private practice here, too.

He has been concerned that, while the wasps being used in the past provided control of house flies, not all species of fly on the Island were being attacked, and biting flies continued to drive carriage horses crazy on hot summer days. So he started looking around for other ideas.

"I became much more knowledgeable about fly control, so that I could find out what ideas worked the best," he told the city's Finance Committee this summer. "Because biting flies propagate on decaying organic material, they have a more sophisticated place to lay eggs and raise maggots. You have to understand that dynamic."

In other words, wasps released in stables and pastures were not reaching horse flies and other biting flies that might be breeding elsewhere.

While the number of house flies has been reduced in the last few years, according to Dr. Sibinic, biting flies still pose a problem.

"Biting flies can cause disturbances and agitate horses," he said. "The city has been doing a great job with cleaning up garbage and manure, but biting flies propagate in different areas that people might not think of."

He learned about a supplier who could also target the biting flies from his cousin, a dairy farmer in Charlevoix.

The city approved the new wasp program July 18, and Spaulding Laboratories of California is now providing four species of predator wasps that will hatch at staggered intervals over a month and deliver seven times the number of wasps than were previously used here, said Dr. Sibinic.

Horse owners Candi Dunnigan and Trish Martin, who met with Dr. Sibinic and the city's Finance Committee in July, agreed that biting flies are an inconvenience, especially in late summer.

"We put out 12 fly traps, but it's still terrible on hot and humid days," Mrs. Dunnigan said at the meeting. "The flies come up from the beach, and they're even out by the airport."

Biting flies breed in unexpected places, such as grass clippings and other compost. Dr. Sibinic urged residents to dispose of lawn cuttings right away, so they can be dried out to prevent flies from breeding there.

"People think the problem is manure, but it's not," he said. "Places that compost effectively, like the solid waste center, turn their compost every four to five days, which is effective."

The heat in compost kills the fly larva, but once they metamorphose into a pupa, Dr. Sibinic said, the fly is going to hatch in eight days, as long as the temperature is 78 degrees or warmer.

Another factor that contributes to biting fly propagation is hay bales. Instead of buying square hay bales, horse owners are buying more economical round bales. Round bales tend to fall apart, Dr. Sibinic said, and excess hay is a breeding ground for flies.

Fly predators attack longterm and are more environmentally friendly than pesticides, he said. Pesticides can kill beneficial insects and release harmful toxins into the air.

"This system works 24 hours a day, seven days a week," Dr. Sibinic said. "A lot of places use repellent, and it might keep the flies off for a while, but it has to be reapplied. This way, you're breaking the biological cycle."

City Fly Control Officer Mike Lee has been working with Dr. Sibinic to distribute the new wasps. He scatters 10,000 wasp larvae around the city each week and says it is a good partnership because he takes care of the city and Dr. Sibinic takes care of private barns.

"I'm glad he's helping out," Mr. Lee said. "It's great that he knows other places we can go to wipe out the problem."

Anyone interested in purchasing fly predators can do so from the city, where a bag containing 1,000 insects costs $1.25. Smaller places, like backyards of private homes, need 5,000 wasps a week, so cost is kept to a minimum, Dr. Sibinic said.

A drawback to the new company, said Mayor Margaret Doud's assistant, Kelly Bean, is that the new wasps cost almost five times more, sending the annual wasp budget from $1,000 to $5,000. Horse and barn owners, she said, have contributed the difference this year.

The city agreed to move to the new company for the remainder of this year and will implement a full change next year. Residents should start seeing a difference in the fly population this month, Dr. Sibinic said.

The most important thing to remember about fly control, Dr. Sibinic said, is that the whole community is responsible for it.

"It's not going to be just the wasps that make a difference," he said. "You have to change your habits."

Return to top

Click here for digital edition
2008-08-30 digital edition