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Wednesday - June 23, 2010

From: Lake Orion, MI
Region: Midwest
Topic: Non-Natives, Pests
Title: Insects on non-native euonymus in Lake Orion MI
Answered by: Barbara Medford


I had a greenlane euonymus that had a few flies last year but was infested with thousands this year. We ripped it out, it was an 8 year old plant. Do you know why they are attracted to it now?


We are a little confused; did you say you cut down the Euonymus fortunei 'Green Lane' and the  flying pests are still around? Maybe we can explain that.

Not very long ago we were asked why flies and wasps were hanging around a magnolia tree. In our research, we discovered that the magnolia is often infested with scale insects. This was followed by the this explanation of why the flying insects were attracted to that magnolia and, no doubt, to your euonymus.

"Another indication of magnolia scale results from the large quantities of sap sucked from the plant as scales feed. The sap provides a low-protein, high-sugar diet, and in order for the scale to obtain adequate amounts of protein, the insect must ingest excessive amounts of sap. Much of this sap is excreted by the scales, which produces a clear, sticky, sugary substance known as honeydew.

This honeydew coats twigs, leaves and anything under infested branches, including cars and patio furniture. If the honeydew is not removed, a more obvious, unattractive black fungus known as sooty mold begins to grow. This is often the first symptom of infestation that people notice. Yellow jackets, wasps and ants also are good indicators of infestations as they are often attracted to the sweet honeydew on which they feed."

The euonymus is susceptible to Euonymus Scale, as discussed in this Penn State Entomology article Euonymus scale. The 'Green Lane' is a selection or variety of Euonymus fortunei as discussed in these two articles from universities:

Euonymus fortunei 'Wintercreeper'  From University of Massachusetts Extension

Euonymus fortunei 'Wintercreeper' from Ohio State University

Because it is non-native, originating in China, this plant is not in our Native Plant Database. Because it is so susceptible to scale, it would be much better replaced with a plant native not only to North America, but to the area around Oakland County, MI in USDA Hardiness Zones 5b to 6b. The scale insect, Unapsis euonymi, is also non-native, having been imported from Japan and China, possibly on some of the imported  bushes.  Native plants have built up their resistance to native insects, as well as a certain amount of co-dependance as in pollination, over millennia. Native plants have also learned to live with the environment they are in, and require less water, fertilizer and maintenance to do well. If the flying insects are still hanging around, it is possibly in order to "farm" the honeydew being produced by scales on other plants. Treat the plant, hopefully get rid of the insects. 



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