Regional Pest Watch: Pacific Northwest
Regional Expert: Nicole Sanchez, Associate Professor of Horticulture, Oregon State University
Mountain ranges create diverse growing environments here, with one side having fertile soil and regular winter rainfall, while the other is dry and arid. Our regional expert shares a couple of pests that can wreak havoc on your garden in the Pacific Northwest and one that is rising in the area to watch out for.
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European earwig (Forficula auricularia)
These red-brown ⅝-inch-long insects with long or short cerci (the pincerlike appendage in back) are most active in spring through fall and have one or two generations per year.
What European earwig eats
Though earwigs eat aphids and other insects, they also feed on seedlings, flowers, foliage, soft fruit and vegetables. Fast moving with a big tail-end pincer, this insect also has the startle factor when it darts out from under foliage or a container.
Damage to look for
Earwigs are most active at night, chewing holes in fruit, flowers and leaves. This voracious pest can decimate entire plants or a row of seedlings in a single feeding, then hides during the day.
Integrated pest management (IPM) tips
Professor Sanchez finds this homemade trap helpful in reducing earwig damage: She fills an empty 16-ounce plastic container about a third full with vegetable oil, adds a little soy sauce and cuts a few ½-inch holes in the lid before putting it back on the container. Then she digs a hole and positions the container flush with the ground. The soy sauce lures earwigs into the trap, where the oil smothers them. Each morning she empties the trap and sets it again for another night.
Bronze birch borer (Agrilus anxius)
Slender green-bronze ⅜-inch-long flathead beetles are most active in early summer and produce one generation of ¾- to 1-inch-long cream larvae per year.
What bronze birch borer eats
This beetle is a serious problem in the Pacific Northwest, killing birch (Betula spp. and hybrids) trees of all kinds, especially white-barked types. River birch (Betula nigra) seems to be somewhat resistant.
Damage to look for
Sparse yellow foliage and twig dieback in the upper crown are an early clue that bronze birch borer larvae are burrowing through a tree and disrupting its nutrient flow. The decline can be reversed if you catch it early, but if more than 50 percent of the crown is damaged, it likely can’t be saved. Look for small ⅛- to ¼-inch D-shaped exit holes in the bark where adults have emerged or zigzag lines on the bark.
IPM tips
Drought stress makes birch trees especially vulnerable. Keep them growing strong by choosing a planting spot on the north or east side of the house, where it’s cooler, watering during dry spells and providing a 2- to 3-inch layer of organic mulch.
Look out for this rising pest in the Pacific Northwest:
Japanese beetle (Popillia japonica)
Shiny green and bronze, this ⅓- to ½-inch-long beetle is most active in early to midsummer and produces one generation of C-shaped ⅛-inch- long white grubs per year.
What Japanese beetles eat
Japanese beetles have become common in the Eastern United States and Midwest but are only now making their way into the Pacific Northwest. It eats hundreds of different plants, but rose (Rosa spp. and hybrids), canna (Canna spp. and hybrids) and hibiscus (Hibiscus spp. and hybrids) are some favorites.
Damage to look for
Metallic-looking adults feed on the flowers and upper surfaces of leaves and skeletonize them. Flower petals have holes or are completely consumed. While the damage looks bad, it doesn’t usually kill the plant. Larvae nibble on turfgrass roots below ground, which causes brown patches in the lawn.
IPM tips
Protect small plants with row cover from June to September when adults are active. You can also pick and drop adults into a bucket of soapy water. Avoid pheromone traps — they attract even more beetles. To create a less hospitable environment for egg laying and young larvae, don’t water your lawn in mid- to late summer.
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