Marianne Ophardt: These insects can be garden helpers

For the Tri-City HeraldAugust 8, 2013 

Every night when I water my container garden flowers, I often am “stung” at least once by a minute pirate bug.

They don’t actually sting, but it hurts because they are inserting their beaks into the skin. They don’t inject venom or saliva, but it is uncomfortable.

Minute pirate bugs are small, only about 1⁄8 to 1⁄5 inch long, with an oval shape and flattened back. Their bodies are black with white markings.

What are these little guys doing in my flowers? They are considered beneficial because they feed on other insects. Their diet includes thrips, psyllids, aphids, chinch bugs, spring tails, plant bugs, whiteflies, spider mites, insect eggs and little caterpillars. They also feed on the eggs and young larvae of corn earworm.

They even are used in some greenhouses to help control thrips. I would guess they are eating flower thrips in my container garden. So even though these guys occasionally annoy me, I see no need to get rid of them.

A less common insect found its way into my office after a WSU Master Gardener discovered it on the leaves of her poplar tree. It is the bumble flower beetle.

It’s a scarab beetle that is a little more than a half-inch long and not quite as wide. It’s not distinctive because of its coloring, which is yellow-brown to red-brown with rows of small black spots on its back. A closer look reveals a hairy head, thorax, underside and legs. It gets its name from the loud buzzing noise, similar to that of a bumble bee it makes when flying.

The beetle generally is considered a beneficial insect because its larvae (white grubs) feed on rotting organic matter. The adults are attracted to sweet and fermenting plant juices. They also are attracted to the fermenting sap that oozes out of the trunk of willow or poplar trees infected with slime flux disease.

Generally, the beetle is not considered a pest. When found on damaged fruit, it usually is there because of the fermenting plant juices and only occasionally causes damage to ripe sweet corn and fruit.

You may not want to handle the live beetles because they give off a defensive chemical that smells a bit like chlorine.

-- Marianne C. Ophardt is a horticulturist for Washington State University Benton County Extension.

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