Green Notes: What Works – and Doesn’t – on Mosquitoes

Some claim that arborvitae trees, known locally as white cedar, may have some mosquito-repellent qualities. 

Mark Konlock, horticulture director of the Green Bay Botanical Gardens, said he has seen no scientific proof that any growing plant keeps mosquitoes away from people. Plus, shrubs and trees provide shade and shelter for mosquitoes.

“Even if a plant has an essential oil or something in it that would repel a mosquito, it’s in the plant and probably not being exuded in enough quantities to deter them from flying around that area,” he said.

Konlock said the botanical garden staff does not fog or spray for mosquitoes, so, he said, “I kind of suffer them.” Or, he tries to stay in windy, open spaces when they’re active, such as at dawn and dusk. The carbon monoxide that humans exhale attracts mosquitoes no matter what.

Konlock favors dropping “barley dunks” into tiny ponds and still-water locations because bacteria in the barley-flake or barley-straw product kill mosquito larvae and can hold down a generation of mosquitoes.

“Scientifically, if there’s stagnant water the mosquitoes can breed in, they’re probably going to do it and then fly around,” he said. 

As of mid-July, mosquitoes had not been too bad in Door County, according to Eric Hyde, superintendent of Peninsula, Newport and Rock Island state parks. A dry spell in June and the timing of rains in July held populations down, but some people still try to repel mosquitoes with ineffective sonic-emitting devices. 

The park prohibits the use of foggers and lawn sprays, which kill other insects as well. Instead, it encourages relying on natural predators – and thus the park’s bat house at Welcker Point – or using tried-and-true mosquito repellents and sitting by a campfire.

He said the biting flies, or blackflies, at Rock Island were not bad in early July, but they were brutal when he visited on July 15.