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Beneficial Insects and Spiders of Alaska is available in very limited quantities from the Cooperative Extension Service.Pam Compton, IPM technician for the Cooperative Extension Service in Mat-Su, recently gave a class on beneficial insects at the CES office in Anchorage. It was the first of three presentations on insects to be offered this summer by the CES.
She had some interesting facts. For instance, did you know that of the over 9 million species of insects in the world, approximately 90% are beneficial, if not to us then to the food chain. Of all the insects in Alaska, fewer than 2% have been identified. There is practically no data on insects in Alaska. This is pretty amazing.
A hungry lady beetle larva converges on aphids. Photo by Jim Kalisch/University of Nebraska Department of EntomologyLady bugs or lady beetles. Probably the best-known of the beneficials. Who hasn't released at least one bag of lady beetles into their garden or greenhouse? There are 23 different species of lady beetle in Alaska but they are probably not all native to the state. Lady beetle larvae, which look a little like an armored prehistoric animal, can eat 10 to 25 aphids a day. They will only stay around if there is a food source.
Ground beetles eat caterpillars and other insects. Rove beetles are general feeders but there is one species that eats slugs! However Pam wasn't sure if that species was in Alaska. (Darn!) They also eat fly eggs and maggots. Beetles pupate and overwinter in the soil. Maintaining permanent plantings, mulching, wooden decks and walkways are ways to attract and protect beetles in your yard.
Green and brown lacewings can lay several hundred eggs at a time. The eggs are anchored by fine threads to leaves and look like tiny elongated helium balloons. The larvae actively hunt and feed by injecting a poison into prey to stun them before feeding. Lacewings are important predators of aphids, whiteflies and mites. Plant nectar and pollen flowers to attract them.
Syrphid flies are not predators but they lay their eggs among aphids as a food source for the larvae. Julie Riley says that syrphid fly larvae look like "green jelly blobs" to her. Syrphids can go through 2-3 generations in an Alaskan summer. Pollinating adults are attracted by flowering plants throughout the summer.
Most of the 4000 species of wasps are parasitic, meaning they lay their eggs in other species of insects to incubate and feed the eggs, which then kills the host. Many wasp species are host speciific making them important bilological controls in nature (think birch leaf miners) and the greenhouse. Have you ever seen what looks like mummified aphids? Or dry aphid skins? You are probably seeing the work of parasitic wasps.
Dragonflies and damsel flies are attracted by water.
Predatory mites are a little rounder and faster than spider mites. They feed on spider mites, thrips and the eggs and nymphs of fungus gnats.
The orb weaver spiders are some of the largest to be found in our gardens. Fran Durner photo Spiders are probably the most important of all garden creatures. They feed on a wide variety of insects, including slugs! Areas with lots of foliage will be attractive to spiders.
Although most of us consider yellowjackets to be pests, they are actually very efficient predators. Worker yellowjackets will eat flies, aphids and caterpillars among other garden pests. (As well as any meat or fish you have out at the barbeque.)
A rule of thumb here - always identify and know what you've got before destroying any funny looking insect. You may be killing the best aphid eater in your garden. If you are using a spray, sometimes the beneficial insect is more susceptible than the pest to the insecticide.
The Cooperative Extension Office will offer a hands-on bug lab on July 16 from noon - 1:30pm. A class on slugs and snails will be held during the same time period on July 23. Call them at 786-6300 to reserve your space.
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