All Posts   Posted:   September 25, 2019 by Nicole Forbes - Dennis' 7 Dees Education Director

Late summer/fall flurries of ash whiteflies have been noticed in the Willamette Valley for the past 5 years or so, and this year, they have returned.

According to the Oregon State University Extension Service, two natural enemies of this annoying little pest have been detected in the Portland area; one is a tiny parasitic wasp (Encarsia inaron) and the other is a type of lady beetle (Clitostethus arcuatus). Experts predict that these two whitefly predators will reduce the pest’s population significantly over the next one or two years and eventually get them under control.

In order for these "good bugs" to do their work, the state strongly urges homeowners not to use pesticides in attempt to control the invasive whitefly, because spraying could kill its enemies as well. Recent studies indicate that the ash whitefly hasn’t done much damage in Oregon, though it can cause curled or stunted leaves and, in some cases, defoliation and death.

Although there is a long list of plants the pest prefers, there is evidence that it has been reproducing on Oregon ash, ornamental pear, hawthorn, and flowering quince. Boxwood, barberry, cistus, rhododendrons, azaleas, and pyracantha appear to attract the insect, but it doesn’t reproduce on these plants. In the fall, populations become more noticeable as the whiteflies move from the deciduous plants they prefer in summer to evergreen shelter for winter.

For more information, go to http://oregonstate.edu/dept/nurspest/Ash_whitefly.html.

Late summer/fall flurries of ash whiteflies have been noticed in the Willamette Valley for the past 5 years or so, and this year, they have returned.

According to the Oregon State University Extension Service, two natural enemies of this annoying little pest have been detected in the Portland area; one is a tiny parasitic wasp (Encarsia inaron) and the other is a type of lady beetle (Clitostethus arcuatus). Experts predict that these two whitefly predators will reduce the pest’s population significantly over the next one or two years and eventually get them under control.

In order for these "good bugs" to do their work, the state strongly urges homeowners not to use pesticides in attempt to control the invasive whitefly, because spraying could kill its enemies as well. Recent studies indicate that the ash whitefly hasn’t done much damage in Oregon, though it can cause curled or stunted leaves and, in some cases, defoliation and death.

Although there is a long list of plants the pest prefers, there is evidence that it has been reproducing on Oregon ash, ornamental pear, hawthorn, and flowering quince. Boxwood, barberry, cistus, rhododendrons, azaleas, and pyracantha appear to attract the insect, but it doesn’t reproduce on these plants. In the fall, populations become more noticeable as the whiteflies move from the deciduous plants they prefer in summer to evergreen shelter for winter.

For more information, go to http://oregonstate.edu/dept/nurspest/Ash_whitefly.html.