Marianne Ophardt

Garden Tips: Aphids not shy about garden takeovers

What's bugging you? Our mild winter and extraordinarily cool weather this spring has allowed some garden insect pests to thrive. One group of these pests is what I call "nasty little suckers," or aphids.

The thing that makes aphids so insidious is that most are ready and waiting to attack as soon as new growth emerges. Plus, they have an extraordinary capacity to multiply quickly. If gardeners aren't vigilant, a small population of aphids quickly can get out of control.

Identifying aphids isn't as easy as you might think, since their appearance varies. Many gardeners are familiar with green aphids and are surprised to find that there also are black, pink, yellow, blue-gray and whitish aphids. Aphids have pear-shaped, soft bodies and usually are less than 1/8 inch in length. Most aphids don't have wings unless their population becomes crowded and they need to find a new feeding site.

Aphids have piercing-sucking mouthparts that allow them to tap into and suck out plant sap. They often excrete a sugary liquid called honeydew, leaving sticky, shiny spots on lower leaves and objects.

When checking for aphids, examine the stems and leaf undersides of new growth. Aphids don't scurry away like other insects; they just keep sucking away.

Besides the bother of honeydew, aphid feeding can injure plants if an infestation is severe, making leaves turn yellow. Many aphids also inject saliva into the plant causing curling, stunting, puckering and distortion. Aphids also damage some plants by transmitting viruses.

What can you do?

1. A forceful spray of water will knock aphids off a plant. Those knocked off will not go back to the plant.

2. Work with nature by encouraging natural predators like ladybugs and their larvae and not using pesticides harmful to beneficial insects.

3. Aphids are fairly easy to kill, but many softer or organic insecticides such as insecticidal soap only work when it directly contacts the bodies. When using these materials, it's important to apply them where the aphids are found. If aphid-feeding already has caused leaf distortion, the aphids stay protected inside the curled leaves, leaving insecticides ineffective.

4. There are systemic insecticides available, applied as sprays to the leaves or as drenches to the roots, that get into the plant sap and kill the aphids. This is the only way to kill aphids protected by curled leaves. However, most of these products are only labeled for use on ornamental plants, not fruits or vegetables.

5. If the aphids are on a woody plant, consider applying a delayed dormant oil spray early in the spring just before the buds open. This can kill overwintering aphids before they get a chance to start feeding or multiplying.

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

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