Wooly Aphid Infestation

By: Patricia Jones

Question: What pest is white; cottony in appearance; sucks sap; and leaves behind a honeydew on plant leaves?

Answer: It depends!  In this case, it is the Wooly Aphid.

We first had an infestation of them in 2022, when hundreds (thousands?) of them tumbled down from an overhanging cottonwood tree.  They littered our deck floor and turned it nearly white.  (For reference, we live in northern Milwaukee County, about 6 blocks west of Lake Michigan.).

 Stumped as to what these pests might be, I contacted Wisconsin Horticulture at UW-Extension, which had me drop off samples at Boerner Botanical Garden.  The State Entomology folks then confirmed that the insect was a wooly aphid.

These winged creatures have shown up in droves again this year.  The dead ones, with wings collapsed in on their bodies, could almost be mistaken for mealy bugs.

Now that our orchids are outside for the summer, the wooly aphids have landed on the plants’ leaves.  Cattleyas, with their fleshy leaves, seem immune to these pests, but thinner-leafed orchids, such as my Phragmipedium Peter Croezen and species Cymbidiums, are more at risk.  I hose down all orchid plant foliage, which removes the honeydew and the aphids, dead or alive.

Some helpful links on wooly aphids and mealybugs can be found in the links below.

https://leafyplace.com/woolly-aphids/

https://en.wikipedia.org/wiki/Eriosomatinae

https://hort.extension.wisc.edu/articles/mealybugs/

Below is a live wooly aphid on a cherry tomato plant this June: 

Wooly Aphid