Garden Detective

No luck against no-see-ums

Black valley gnats, a.k.a. no-see-ums, feed on blood.
Black valley gnats, a.k.a. no-see-ums, feed on blood. UC Davis Bohart Museum of Entomology

Q: I’m trying to find out how to control a no-see-um insect. My neighborhood is overrun with them. At first, it was just in the early morning and at night, but now it’s all the time. I contacted Vector Control and they said it was a type of fly. I’m just trying to control them in my yard. I’ve tried using repellents, but I haven’t seen any difference. It has gotten to the point that I can’t go out in my backyard at any time. If I go out into the front or walk down the street, I get some, too.

Ken Kramlich, Sacramento

A. According to UC master gardeners Annie Kempees and Mary Griggs, no-see-ums (Leptoconops torrens) are common in parts of California’s Central Valley, particularly in areas with alkaline clay soils. No-see-ums are so nicknamed because of their near invisibility.

The adults are black and tiny, about  1/16 -inch long, and are small enough to pass through window screens. The adults breed when the weather warms up in the spring, usually in early or mid-May, and they remain a pest for several weeks. When the soil begins to dry and cracks develop, the adults emerge.

Only the females bite. Like female mosquitoes, they need a blood meal to complete their reproductive cycle. No-see-ums bite humans, animals and birds.

They have short mouthparts and the females feed by injecting saliva into the skin, which pools the blood just beneath the surface. The bite is generally painless and the host feels no sensation during the first 30 to 60 seconds of the bite, but within 12 hours, the bite becomes excruciatingly itchy.

There’s not much you can do when they feed except to stay away from them. Don’t sit long in places where they are likely to occur or where you’ve heard they’re a problem.

The best strategy to prevent no-see-um bites is to wear long-sleeve shirts, long pants, shoes and socks, and a hat during times when no-see-ums are most active. Choose lighter colored garments and consider hats with fine meshed netting.

No-see-um-proof netting is also available (usually at sports or outdoor equipment stores), and outdoor equipment companies market head nets, jackets and pants made from this material. These products may come in handy depending on your preferences and outdoor activity.

Of course, these same strategies are also effective against mosquitoes and black flies.

Garden questions?

Questions are answered by master gardeners at the UC Cooperative Extension services in Sacramento and Placer counties. Send questions to Garden Detective, P.O. Box 15779, Sacramento, CA 95852. Send email to h&g@sacbee.com. Please put “Garden Detective” in the subject field and include your postal address. To contact UC Extension directly, call:

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