wpostServer: http://css.washingtonpost.com/wpost2

Most Read: Local

Posted at 11:35 AM ET, 07/26/2011

The scoop on gnats: the weather they like & why they drive us nuts


A Fungus gnat ( Maine.gov )
They hover around your eyes, ears, nose and mouth. They slowly devour the roots of your houseplants. They levitate in swarms called ghosts, haunting stream beds and forests throughout the region.

No matter what type of gnat you’re looking at, one thing is for sure: gnats are annoying. Anyone who has swallowed a few while biking along Rock Creek at dawn or dusk can attest to that.

What is it about summer that entices these tiny flies to wake up and smell the … rotting roses? Gnat larvae live in moist environments. Given the average annual precipitation of 40 inches and ample waterways and wetlands in the DC region, finding the perfect gnat breeding site does not seem to be a problem.

With no end to heat and humidity in sight, perhaps Capital Weather Gang should create another daily forecast for our readers who are outdoor enthusiasts: the GnatCast.

You may think a gnat is just a gnat. But to an entomologist, it’s a fungus gnat, eye gnat, gall gnat, sand gnat, or any number of other small biting flies that are often mistaken for gnats, such as the fruit fly.

Gnats are small flies of the suborder Nematocera, which also includes midges, craneflies and mosquitoes. Whether we like them or not, gnats serve a purpose in nature. They are an important food source for birds, bats and larger insects. They also pollinate flowers.

They are not blood-thirsty like their cousin the mosquito. In fact, some adult gnats don’t even eat during their short lifespan. Gnat larva, which hatch from eggs laid in moist soil and other wet environments, feast on fungus, algae or plants.

Besides humidity, a gnat’s life cycle also depends on temperature. Take fungus gnats , for example. The fungus gnat – a common indoor pest that thrives in the overwatered soil of potted plants or greenhouses – lives out its life cycle in three to four weeks at temperatures of 77 degrees Fahrenheit or higher. Temperatures that are too hot can kill them (some horticulturalists have used a ‘bake-out’ method to rid greenhouses of fungus gnats by heating the soil to a temperature the gnats cannot withstand). On the other extreme, fungus gnats that live in Alaska can survive temperatures lower than 25 degrees below zero by freezing their bodies.

Gnats and related flies are so in sync with weather conditions that one team of scientists from the University of Liverpool has been analyzing fossilized midge heads to determine past climate events.

Ridding our homes and gardens of gnats can be a challenge, both indoors and out, especially after above average rainfall and relentless humidity and heat. Keeping storm drains unclogged and getting rid of standing water on your property may help. Try not to bring outdoor potted plants indoors. If your indoor plants become infested, let the soil dry out for a few days before watering again. Gnats in natural areas may be attracted to sweet scents, such as perfume and soaps, so avoid spraying yourself with strong-smelling products before heading outside.

Are gnats a nuisance to you this summer? Let us know and share your tips for getting rid of them by posting a comment below.

By  |  11:35 AM ET, 07/26/2011

Categories:  Posegate, Nature, Latest

 
Read what others are saying
     

    © 2011 The Washington Post Company