Expert Advice on Moving Out Mosquitoes

The new year brings new cases of Dengue fever, with five more added to the list last Friday, another one identified in the Department of Health’s update Tuesday, and six additional cases Thursday.  That brings the total to 230 Dengue cases in Hawaiʻi since September.  Three of the confirmed cases are potentially infectious.

The biggest concern remains on the Big Island of Hawaiʻi  where health officials are investigating the first cluster of locally-acquired dengue fever since the 2011 outbreak on Oʻahu.   Of the confirmed cases, 202 are Hawaiʻi Island residents and 22 are visitors.

182 cases have been adults; 42 have been children under age 18.

The Dengue outbreak, which started Sept. 11, is now the largest since statehood.  Hawaiʻi’s second-largest outbreak was in 2001, when 122 confirmed cases were reported.

Two types of mosquitoes transmit the virus, and all mosquitoes lay their eggs in water.  Excavation and landscaping expert Shayne Edelhertz has met many a mosquito, and says the bugs look for any standing water they can find.

“They’re borne in water.  It’s an ingestion period of water for maybe two days, and then they hatch out of the water and become airborne,” explains Edelhertz, who owns Country Excavation on Maui. “So to get them before that happens, you can come across a five-gallon bucket with 1,000 mosquito larvae getting ready to jump out of there.”

Whether the issue is illness prevention or just inconvenience, reducing the number of bugs on your property is important.  And that means maintenance.  Edelhertz says vacant sites should be cleared every three to six months.

“Within a three to six month growth, you can create a habitat for a few million insects, as well as breeding ground for mosquitoes,” he says.  “We’ll cut a path through an unmowed area and it’ll be like a stampede of insects and rodents, which are quickly eaten up by the egret birds.”

In wetter areas, the slope of your property also makes a difference as to where and how well the water drains.

“If your property wasn’t graded initially, it can saturate in low-lying areas and create puddles of water that you may not see,” Edelhertz explains.  “So you can fill in those lower areas to try to make the water drainage; ideally, it’s good to have a property that’s well-contoured to account for the water that comes to it, to shed it to either a stream that has moving water or any area that will dissipate it quickly.”

While mosquitoes will opt for standing water pretty much anywhere, some plants make it easier.  For instance, Edelhertz says invasive cane grass can hold moisture and provide a great harbor for bugs, while Elephant Ear plants can grow very large and catch water easily.

“When you have rain nonstop every day, they’re gonna fill up with water and create breeding grounds,” he says, “so unless you have a specific purposes for these types of plants around, you’ll want to limit them to out-of-the-way areas, or maintain them.”

Other plants, along with essential oils like peppermint and clove, can naturally repel mosquitoes.

“Citronella is one that grows well in a potted area closer to your house,” he explains.  “The eucaplyptus trees when maintained can also create an oil and a smell that deters mosquitoes and other bugs.”

Eucalyptus wood chips are more beneficial that other wood chips, but Edelhertz says don’t forget they will decompose.  That could attract centipedes and other insects, so keep the chips away from your house, sprinkle them around trees or a garden, and replace them every three months or so.

Don’t count out drier climates, either, says Edelhertz.  Since it doesn’t take much water to breed mosquitoes, make sure trash cans and even little cans of water are covered.

“It’s such a welcoming environment, all you have to do is add a bucket of water or a little shade to a well-sunned area and you’ll have a mosquito environment,” he explains, adding that ornamental ponds need to stay in motion.  “People that have small ponds, you want to introduce either mosquito-eating fish or frogs that eat mosquitoes create an environment for them; have that pond be moving with a small solar pump or 12-volt pump that can recirculate the water.”

Edelhertz says keeping invasive plants and bugs under control should be a priority for all of us.

“It’s your responsibility, it’s your kuleana to watch out for the land, and maintain it so that the people around you as well as yourself are in a clean, safe environment,” says Edelhertz.

At the state level, health officials continue to routinely monitor for cases of imported dengue infection on all islands, and will have Vector Control perform mosquito site assessments and abatement as needed.   The Hawaiʻi Department of Health is holding weekly information sessions in Kona and Hilo to provide timely updates and answer questions from the community. Participants will learn about the prevalence, transmission, and symptoms of dengue fever, outbreak response efforts, how to interpret case counts and maps, and the best ways to Fight the Bite.

A different mosquito-borne infection also made headlines last Friday.  A baby was born in an Oʻahu ospital with a neurological condition called microcephaly, and tested positive for the Zika virus, which health officials say can have serious health impacts. But they add there is no risk of transmission in Hawaiʻi.