Scrub Hub: What is mosquito control, and does it hurt the environment?

With the approach of summer and warmer weather, hordes of mosquitoes are just waiting for Hoosiers to bare a bit of skin.

The pests are laying eggs in standing water even as you read this and with the oncoming swarms that will soon follow come a vast assortment of ways to keep the bloodsuckers at bay. From healthy doses of DEET to home remedies made from essential oils, people are keen to deter the buzzing beasts.

While these might be options for picnickers and hikers, local mosquito control, as well as some private businesses, lend their support in the broader battle against the potentially disease-carrying bugs.

For this week’s Scrub Hub, we set out to find what widespread measures are used to control mosquitoes that could potentially be carrying diseases such as West Nile Virus — and what effects those efforts can have on the greater environment.

We spoke with the Marion County Health Department and the Office of Indiana State Chemist about techniques local agencies and private businesses use while trying to control mosquitoes and how they are monitored.

Short Answer: Balancing public health with environmental stewardship

Health departments and private businesses use sprays to control mosquitoes, but both go about it a bit differently.

In Marion County, the health department’s mosquito control program is broken up into a few different parts.

Matt Sinsko, coordinator for vector-borne disease prevention at the department, said there are two operational programs during the summer: finding breeding grounds (larviciding) and killing adult mosquitoes (adulticiding).

“We spend most of our time and energy trying to find areas of standing water where mosquitoes are breeding,” Sinsko said. “If we can find those sources and kill mosquitoes while in the water, we’re going to have much more success reducing the population.”

The county mostly uses a mineral oil for larviciding, Sinsko said.

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The product spreads along the surface of the water and prevents mosquito larvae from breathing the air above the water. The oil breaks down in sunlight, Sinsko said, and is gone within 24 hours. The quick breakdown of the product means it’s not a perfect solution since mosquitoes will once again be able to use that spot to breed.

Other aquatic insects don’t breathe the same way as mosquitoes, so they are not affected by the oils.

The control program also uses separate insect growth regulators during larvicide operations that could affect something like dragonfly larvae, Sinsko said.

“We try to use that only when we feel like it’s necessary in certain environments,” he said.

The health department uses ultra-low volume machines set up on the back of trucks to spray droplets of an adulticide at night. This technique, sometimes called fogging, sprays out carefully calibrated droplets, Sinsko said.

The droplets stay aloft for about 10 minutes and will kill mosquitoes on contact. Just as the mineral oil used for larviciding, this technique does not have any residual effects, meaning once the droplets fall or evaporate, the pesticide is no longer able to kill mosquitoes.

Beekeepers and residents will call in with concerns during these sprays, Sinsko said, but because bees are not active at night when the trucks are spraying, there are no adverse effects. And even if the pesticide falls onto flowers the bees would use for pollen, it won’t be active by the time bees wake up and visit it.

It’s likely, however, that a private lawn care company or pest control business will not be spraying at night, but during regular working hours.

Long Answer: Complications can arise during daylight sprays

The Indiana State Chemist Office’s pesticide program gets complaints of errant sprays going to properties it was not intended to treat, David Scott, administrator of that program said.

Case documents from the state chemist details some of these complaints and resulting investigations, usually resulting in warnings or fines up to $250. The state can sample various items around the non-targeted yard to test for pesticides to determine if any made if off the targeted property meant to be treated.

While the Marion County Health Department will conduct its adulticide spraying in the evening when mosquitoes are active and other insects or not, Scott said most residential treatments are done during the day.

“Bees usually forage during daylight hours before dusk,” Scott said. “You’re likely to directly contact bees during the day and more likely to contact adult mosquitoes at night. Night would be the most opportune time to (apply adulticide).”

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Anyone spaying pesticides in Indiana is bound to state regulations. Scott said the label on every container is a legal document and every user is obligated to following those regulations.

“If you don’t you violate state and federal law,” he said.

Current state regulations require certain users with certain types of pesticides to be certified and licensed.

Community-wide mosquito control programs are usually those associated with a local government’s health department working to allay concerns of disease transmission. Then there are private residential control applications done on a commercial basis meant to get rid of nuisance mosquitoes. These for-hire businesses are a newer phenomenon, Scott said, picking up speed within the last decade or so.

In Marion, the health department's vector borne disease prevention coordinator Sinsko said the program is sympathetic to pollinators and will take measures to avoid spraying in areas where there may be concerns.

“When we know of a beehive, or someone who has hives in their backyard and doesn’t want us to be around, we will try to avoid the area if we can,” Sinsko said. “But we make no promises because we have a mission to control diseases.”

Just because one person may have a hive doesn’t mean their neighbors should be at risk of disease, he said. That’s the fine line the health department walks keeping up with the public health mandate while being good stewards of the environment.

There are some simple, effective and environmentally safe ways residents can help keep mosquitoes away, Sinsko said, and it begins with emptying anything able to hold water.

“We usually stress homeowners taking time to walk around their house and empty anything holding water,” he said. “Things like clogged gutters are notorious for breeding mosquitoes. Kiddy pools sitting out for a couple weeks are also great place for mosquitoes. They can breed right under your nose.”

If you’re planning on sitting out in the yard for a while, Sinsko recommends getting a fan to blow toward you. Mosquitoes are not great flyers, and most will not be able to brave the breeze.

“If you know of things that could be a source of breeding give us a call,” Sinsko said. “Anything you can do to avoid mosquito bites will help avoid infection of West Nile Virus or at the least dealing with an annoying itchy bite.”

Karl Schneider is an IndyStar environment reporter. You can reach him at karl.schneider@indystar.com. Follow him on Twitter @karlstartswithk

IndyStar's environmental reporting project is made possible through the generous support of the nonprofit Nina Mason Pulliam Charitable Trust.

This article originally appeared on Indianapolis Star: Scrub Hub: What is mosquito control, and does it hurt the environment?