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Monday, October 14, 2019  Spokane, Washington  Est. May 19, 1883
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Gardening: Aphids leave imprints on Inland Northwest yard-scapes

Adult aphids feed on the underside of a currant leaf. Their feeding distorts the leaf but doesn’t hurt the plant in the long run. (Pat Munts / The Spokesman-Review)
Adult aphids feed on the underside of a currant leaf. Their feeding distorts the leaf but doesn’t hurt the plant in the long run. (Pat Munts / The Spokesman-Review)

The aphids are loving the cool weather this spring, and they are showing up on all kinds of perennials, shrubs and trees with a vengeance.

Aphids are soft-bodied sucking insects that feed on the underside of leaves. They are pear-shaped about a sixteenth to an eighth-inch long and range in color from green to brown, purple, red and black. Some are generalists while others feed on specific plants. Some are shiny while others have a waxy, cottony covering. Other characteristics include long thin legs, sucking mouth parts, long antenna, and a pair of tiny tubes that project from the bug’s posterior.

Aphids produce several generations a year. They overwinter as eggs in bark cervices and/or on roots of host plants. In the spring, the eggs hatch and are ready to produce the next generation of live young in 10 days. As the colony grows, winged aphids travel from the original colony to a new plant and begin the cycle again.

When the insects feed, their sucking often profoundly distorts foliage and their excrement creates a sticky mess of honeydew that then drips onto anything under the tree. The damage caused by the aphids feeding rarely kills plants but can look unsightly. The honeydew draws ants that often tend the aphids to harvest the sweet solution. The honeydew also attracts a sooty, black mold that just adds to the mess.

Controlling aphids can be a challenge. The first line of defense is to look for plants that are resistant to aphids. This will take some experimentation and research. Light infestations can be dislodged by blasting the insects off the plants with a hard stream of water. This will dislodge them from the plant and interrupt their breeding. Be sure to get the underside of the leaves.

Don’t be too quick to get out the insecticides. There are many predator insects that consider aphids a gourmet meal. As the aphid population builds up, lady beetles, lacewings and hover flies will move in and lay eggs or eat the aphids on the infested plants. They will work for you around the clock for little more than a hospitable habitat.

If a spray is needed, apply an insecticidal soap to the top and bottom of the leaves. It will kill on contact. However, the insecticidal soap will also kill the beneficial predators too so follow the directions for use carefully.

Systemic insecticides applied to the plant’s roots and are taken up by the plant’s vascular system to the leaves where the aphids are feeding. The advantage of systemics is that they will protect the plant for several months and will only harm sucking insects that feed on it.

If aphids attack large trees, it’s time to call in the professionals who will have the right equipment and access to systemic chemicals not available to the homeowner. The best time to call them is August and September so the trees have the winter to pull the chemicals to the top of the tree by early spring.

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