Biodiversity or mosquito fogging: You can’t have both

Ah, the mosquito. It plagues our summers and can ruin our outdoor fun. Is anyone a fan? If so, consider the Asian tiger mosquito, which has no regard for personal space or time. If you happen to have it in your yard, it bites everyone, morning, noon, and night. In winter we long for warm weather, but when it finally arrives, in some neighborhoods we are indoor prisoners. Understandably we want to rid ourselves of this awful pest.

Some of our neighbors turn to commercial-grade mosquito fogging, persuaded by marketing claims that the product is both effective and “safe”. But a closer examination of these claims reveals an ineffective process that is devastating for native bees, butterflies, moths, and a plethora of other beneficial insects we work so hard to attract with native plants.

How effective is mosquito spraying? How effective can it be when the chemicals in the product only target adult mosquitos and only those adults within direct range of the fog? By some estimates, no more than 20-30% of adult mosquitos are killed in one treatment. Meanwhile all mosquito larvae, which are laid and hatched in standing water, are unaffected. They continue to grow and emerge as if nothing harmful has happened in their environment. As a result, the adult population of mosquitos is quickly replenished while nearly every other insect the fog touches is indiscriminately killed.

Mosquito spray producers point to EPA statements that the chemicals are safe for bees when used according to label instructions. But there are severe limitations to the EPA’s testing method. The agency only tests on honeybees and only measures the chemical toxicity resulting from surface exposure, not oral ingestion.

This is highly problematic. Honeybees are only one species of bees and are non-native to boot. That leaves 400 species of native bees in Virginia, along with all butterflies, moths, dragonflies, ladybugs, fireflies, and numerous other beneficial insects that are not tested. Those insects have entirely different life cycles, foraging methods, and ways of protecting and feeding their larvae which render them tragically vulnerable. It is a complete folly to extrapolate EPA’s honeybee-focused test results to any other insect species.

Consider this: One spray of mosquito fog leaves a persistent residue on the surface of everything it touches. Repeating the applications every 10-30 days, as many commercial services recommend, just compounds the problem. The EPA says it considers how long the chemical residue persists in the environment and its effect on honeybee colonies. However, honeybees can forage up to 5 miles away from their hives if necessary, far away from the fogged area and the residue. Our native mason bees, on the other hand, forage no further than 300 feet from their nests. They are wholly dependent on the health of their immediate surroundings to eat and reproduce. Adults have no way to avoid exposure.

Neither do their larvae. Leaf cutter bees and mason bees, for example, produce dough balls that are left in hollow stems for their developing larvae to eat. The balls are composed of pollen and nectar from the flowers in their immediate foraging range. As the larvae hatch and eat the dough balls, they ingest concentrated levels of the pesticides and die. For our native bees, there is no honeybee equivalent of the hive to ensure their survival. They live their lives alone. As their larvae die, all subsequent lines of offspring from affected individuals are gone for good.

Fortunately, as research has advanced on fogging, so too has the thinking on several alternative, inexpensive methods of control. Here are some very safe and effective suggestions, especially when used together as a suite of tools.

Source Removal. The most effective method of mosquito control by far is “source removal,” or emptying/eliminating all sources of standing water on your property. This practice kills mosquito larvae before they become biting adults. Regularly inspect your property for containers or areas that hold water, then remove or empty them. Remember to inspect flowerpots, buckets, or any other feature or item that can hold water. Change the water frequently in places where you want it – like birdbaths – so the larvae have no time to grow and emerge. Maintain your gutters and downspouts so the water flows. Keep your swimming pools and hot tubs clean and properly chlorinated.

Mosquito Buckets: This is a favored method of control by Doug Tallamy, an entomologist at the University of Delaware and national proponent of supporting biodiversity in our own backyards. He recommends filling a five-gallon bucket of water, placing it in the sun, then adding a handful of hay, grass, straw, or leaf litter to decay and attract egg-filled female mosquitos. After they lay their eggs, add a mosquito dunk tablet you can purchase at any hardware store, garden center, or home improvement retailer. It contains a bacteria that kills several species of fly larvae, including mosquitoes. A more detailed explanation of the process - and photos of lovely painted buckets -  can be found on Dr. Tallamy’s Homegrown National Park website.

Ovitraps: Ovitraps, which are available from the same stores as mosquito dunks as well as on Etsy, use scent to attract adult egg-laying females, trap them, and kill both the adults and the larvae they produce.

Water Wrigglers: Water Wrigglers are devices you can purchase to keep water moving in birdbaths. They were designed to attract birds to the sight and sound of running water but are also highly effective in stopping female mosquitos from laying eggs.

Deck Fans: Mosquitos are weak fliers. Turn on a fan while you enjoy your deck and make it harder for mosquitos to reach you.

Personal Protection: When spending time outdoors, consider wearing long pants, sleeves, and a hat, and spraying your clothing and skin with insect repellant. Personal precautions such as these can prevent mosquito bites entirely.

Community Efforts: Mosquito control is very successful when several neighbors in a larger community participate. Talk to your neighbors about source removal, ovitraps, fans, and water wigglers. Show them your homemade mosquito bucket and encourage them to do the same. Some studies tout this approach above all others, suggesting that mosquito populations can be reduced by 85% when the whole street or block works together. One way to approach your neighbors is by inviting them to join a Pollinator Pathway and giving them a nifty little sign to display which will encourage other neighbors to rethink their mosquito-spraying contracts.

We all enjoy our yards and our pollinator gardens, and we understand how including native plants promotes biodiversity. But along with joy comes responsibility. If we don’t protect the very life we’ve helped emerge, no one will. We can have improved biodiversity, or we can have pesticides. They do not co-exist.