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Ash whiteflies: The new invasive species spotted in region

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SUBMITTED PHOTO - Ash whitefly have been spotted all over western Washington County and as far south as Salem. The bugs are a nuisance, but experts say there's little than can be done about them at the moment.They’re everywhere.

Tiny white insects have taken over the Portland metro area over the past few months, leaving residents scratching their heads over what they are, where they came from and what, if anything, can be done about them.

Ash whiteflies, officially siphoninus phillyreae, have exploded in numbers this year, with thousands of the tiny nuisances being spotted across the Portland area.

Robin Rosetta, an Oregon State University associate professor and entomologist, works with nurseries and greenhouses on pest management. She said that the tiny insects were first discovered in Oregon last year, but have greatly increased in numbers this year.

“Aren’t they incredible?” she joked on Monday. “They’re everywhere. They are very abundant.”

Rosetta, who lives in Tigard, said that she has seen large populations across Southwest Washington County, and has received reports that the bugs have been found south of Portland, as well.

“They are down in parts of Woodburn and Salem for sure,” she said. “It’s spotty, still. Not everybody has a population yet.”

Originally from Europe, the species was spotted in California in the late 1980s, and has slowly become more and more common across the country.

Whiteflies were first spotted in the Portland area last year. It’s not clear why the invasive species has bred so rapidly this year, but Rosetta said it is likely a combination of factors.

“Often when a new species comes in, they don’t have natural enemies keeping them in check,” she said. “That’s what we’re seeing. Things are not in balance. They have probably been here longer and nobody noticed them. We had some nice warm weather the last few years which likely let them build up to the numbers we’re seeing.”

An individual bug lives about 30 days and lay eggs on the undersides of leaves.

Although called flies, the bugs are more closely related to aphids and suck nutrients from plants.

The ash whitefly has a wide-range of plants it calls home, including ornamental and native plants as well as fruit trees. Particularly Oregon ash, ornamental pear, hawthorn and flowering quince, though Rosetta said that list will likely grow larger as the creatures are better studied.

Unfortunately, Rosetta said, little is known about what impact the bugs will have in Oregon.

As for getting ready of the pesky bugs, there isn’t much that can be done. Rosetta said that she isn’t recommending that landscapers use spray chemicals to kill the bugs. She said that the population will subside as the weather gets colder.


By Ray Pitz
Editor
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