New Forecasts Could Offer Solution To Swarms Of Pesky Midges

June 10, 2004

GAINESVILLE, Fla. — They may not have the bite of mosquitoes, but midges – those little insects that form cloud-like swarms- can be a major summer nuisance. They can ruin a car’s paint job, contaminate food, cause severe allergic reactions in some people, and even pose hazards on roads and at airports.

Now a group of researchers at the University of Florida has found a way to forecast those swarms, which typically form over lakes and ponds. The forecasts promise to make midge-control programs safe and affordable for communities where the bugs have run rampant, the researchers say.

“Applying pesticides to thousands of acres of lake is something you wouldn’t want to do even if you could afford it,” said Richard Lobinske, a senior biological scientist at UF’s Institute of Food and Agricultural Sciences. “If you can find just those parts of a lake where adult insects are likely to emerge, you can attack the problem with a lot less cost and effort.”

Lobinske and his fellow researchers – UF aquatic ecology Professor Arshad Ali and UF insect ecology Professor Jerry Stimac – published their findings in the May issue of the journal Hydrobiologia.

Often mistaken for mosquitoes, midges are a common summer sight on lakeshores around the world. The insects spend most of their month-long lives as larvae living underwater, then emerge as flying insects in their last few days to mate and lay eggs on the water. When they emerge, they do so by the millions, flying frantically in cloud-like swarms.

While midges are active almost year-round in Florida, their populations swell during the summer months. And their numbers can truly boom in urban lakes, where runoff from fertilizer and other chemicals can boost growth of the microscopic plants on which midge larvae feed.

Most midge species don’t bite, and they are generally considered a minor nuisance. But for many waterfront communities, sheer numbers can make the midge an intolerable pest.

“In some of the worst situations, dead midges can pile up a couple of inches thick over just a few days,” Lobinske said. “When you’ve got that many bugs in your neighborhood, you’ve got a problem.”

The insects are attracted to light, and clouds of midges have been known to enter homes and businesses. Midges are easily inhaled and can get into food as it is being prepared, causing severe allergic reactions in some people. Midge swarms even can pose a driving hazard, covering cars with paint-damaging splatters, clogging air intakes and plastering roads with a slick goo.

“Midges can be a serious hazard to several modes of transportation and not just cars,” Ali said. “For instance, a few years ago the people at Marco Polo Airport in Venice, Italy, called me for help because there was a potential for planes skidding on dead midges heaped on the runway.”

Landowners can prevent outbreaks in small ponds by applying larva-killing pesticides to the water. But in larger lakes, solutions are not so simple. Midge-control chemicals are too costly to apply to hundreds of acres of water, Lobinske said. And because midge outbreaks tend to occur only in small portions of larger lakes, applying chemicals to an entire body of water can harm beneficial organisms and the environment at large.

“As annoying as they can be, midges do play a beneficial role in the ecosystem,” Lobinske said. “The larvae are an important food source for fish and other aquatic organisms. We need to be able to attack the largest emergences without affecting areas that support a normal midge population.”

The researchers found that by sampling sediments and water from three Florida lakes for larvae and other indicators, then using a global positioning system to map the results, they could predict major midge outbreaks in areas as small as 100 acres, about the size of 400 suburban lawns. Armed with such a forecast, a handful of researchers can do a more detailed survey of a potential outbreak area, finding midge hot spots as small a single acre.

Early versions of the researchers’ forecasting method have already been put to use by midge-control officials in Sanford, a town where past midge outbreaks have been so severe that businesses were actually forced to temporarily close.

“There’s still a problem here, though it’s not as bad as it used to be,” said Jonas Stewart, director of the Volusia County Mosquito Control District, which oversees midge control for Sanford. “There was a time when you’d see piles of dead midges on the sidewalk.”

Stewart said the UF researchers’ forecasts would allow the district to limit its use of the few chemicals currently approved for midge control, reducing the chance that midge larvae will develop a tolerance to those chemicals. He said it can also lead to substantial savings for the district, which can spend $30,000 per month killing midge larvae during the town’s worst outbreaks.

“We don’t know of any midge populations that have learned to tolerate these chemicals, but we don’t want to take our chances by using chemicals where they’re not needed,” he said. “More importantly, a good forecast could decrease the time we spend finding the places where an emergence is going to happen, so we don’t spend a lot of time and money in places where there isn’t really a problem.”