BLACKSBURG — State officials want to ensure that Virginians concerned about Zika don’t inadvertently harm pollinators when trying to control mosquitoes.
Mike Weaver, a Virginia Tech entomologist and Virginia Cooperative Extension pesticide safety educator said it’s important to remember that pesticides used to kill mosquitoes can also kill pollinators, including bees.
Last year Virginia beekeepers lost 46 percent of their honeybee colonies to various problems, and native bees also are in decline. Reducing pesticide kills of bees has been a major thrust of public pesticide education for several years, but that work may be threatened.
“Whether Zika comes to Virginia, or not, the hysteria is going to,” said Tim McCoy, a Tech entomology researcher who works with Weaver. “People are either going to be misapplying pesticides themselves, or hiring outfits to just treat, and could end up doing a lot more harm to pollinators than to the mosquitoes themselves.”
Zika infection has been confirmed in 20 Virginians as of the latest reports, involving those who either traveled to an area experiencing an outbreak or who had sex with someone who had, according to government data. Mosquitoes in Virginia have yet to transmit the virus, according to the reports. The Zika virus has been linked to birth defects in pregnant women.
Out of 58 species of mosquitoes found in Virginia, two can carry Zika, according to the state Mosquito Control Association.
Aedes aegypti, also known as the “yellow fever mosquito” specifically targets people as food sources and bites at dawn and dusk. This insect is largely responsible for the global outbreak of Zika, but it is uncommon in Virginia.
Aedes albopictus, known as the “Asian tiger mosquito,” was introduced to Virginia in 1991, according to the association. It has since largely displaced the yellow fever mosquito.
Asian tigers reproduce almost exclusively in artificial containers. The eggs can dry out and remain viable for up to 400 days, hatching when the container fills with water, according to the association.
Tiger adults feed during the day, and aggressively pursue a wide range of victims, including humans, and dogs to which they can spread heartworm, a serious canine infection.
There are several cheap, pollinator-friendly options for reducing tiger mosquito populations without using pesticides.
“Larval control is really the key,” McCoy said.
Inspect lawns and homes for any items that can trap rain. McCoy suggests setting aside one day a week to patrol for any sources of standing water, then dumping them out and scrubbing them to remove eggs.
The list of suspect containers is long and varied, even surprising. A tarp left outside can hold enough water in one of its folds to host tiger mosquito larva.
Plugged gutters, corrugated downspouts and drain pipes, old tires, boats and canoes, birdbaths, flower pots, rain barrels – anything that collects and traps even a small amount of water can become an Asian tiger nursery. In Florida, where McCoy comes from, he said cemetery flower vases are a common breeding ground.
For containers that can’t easily be dumped, Weaver recommends “mosquito dunks,” available at hardware stores and home centers. Made from Bacillus thuringiensis, or BT, a bacteria that damages the guts of mosquito larvae, the dunks are harmless to mammals, birds, bees and butterflies.
The mosquito control association recommends stocking small pools and ponds with fish, which eat mosquito larvae. Adult mosquitoes “rest” in ground covers, under arbors and in shrubs and bushes, so eliminate these habitats when possible. Trim shrubs and undergrowth regularly.
Before considering any chemical treatment, “first, really determine if you need to use a pesticide,” said Liza Fleeson Trossbach, program manager for the Office of Pesticide Services in the Virginia Department of Agriculture and Consumer Services.
“If you have a few mosquitoes, you may be able to just protect yourself. Just because you see a pest doesn’t mean you need to treat,” she said.
Weaver says there are a number of ways to prevent bites from adult mosquitoes. Use fans or citronella products on decks or in outdoor gathering spaces. Personal repellents, such as DEET or pre-treated clothing can also help, he said. Long-sleeved, light-colored shirts and long pants are recommended.
But if your neighbors are less diligent with mosquito control, and you have high numbers of the pests, McCoy recommends doing your own minimal spraying of non-flowering shrubs and ground covers.
There are several things to consider when doing such a treatment. Trossbach said to first make sure the pesticide you use is registered with the state, and that it is the correct pesticide for your purpose. The Office of Pesticide Services’ website includes a searchable database with that information.
But most important, follow the label directions.
“The label is the law,” Trossbach said. “It is a federal law and a state law that the person uses the product in accordance with all the label directions — that’s how much you use, how often you use it, where it’s used.” Following the directions also helps mitigate any risks from the pesticide and helps prevent unintended consequences, such as damage to pollinators, she said.
The mosquito control association recommends spraying in the evening, just before dusk when bees and other pollinators are less active.
Before hiring a company to spray for mosquitoes, check to make sure they are licensed with the state, Trossbach said. All commercial applicator companies must be licensed and every applicator — the person who does the spraying — must be state certified. The pesticide services database lists licensed companies and certified applicators.
Ask questions about what pesticides the company will use, and what their effects will be. Trossbach said any licensed company should be able to answer them.
For more information on mosquito control, visit http://goo.gl/TwJeCY and http://mosquito-va.org.