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Saturday, May 27, 2017

White Cotton on New Growth of Ash

Q. I have a 6-8 yr. old ash that has this white powdery looking substance on the newer growth. Can you tell me what it is and how to eliminate it. Photo attached.
Unknown white cottony insect at base of new ash growth.

Another image of white cottony insect at base of new growth on ash

A. I have to admit I put this on a back burner because I wasn't quite sure what was going on. I have seen this on vegetables and herbs but never on the new growth of ornamental trees. It is most likely an insect problem.

These insects are feeding on the soft, succulent new growth. If you touch this white fluffy substance on these shoots I think you will see these insects beneath it. The problem I had was what to call these insects. At first I thought it was woolly Apple aphid which makes a lot of sense in the cool time of the year when there is new growth.

But what troubled me was that I have never seen woolly Apple aphid in Las Vegas before. I have seen it in other cooler climates.

See some pictures of Wally apple aphid

Secondly, the pattern that they are feeding in does not typically fit woolly Apple aphid. They don't usually feed all along the new growth. They are typically clustered at the bottom of the new growth. Until you tell me differently, I am going to stick with woolly Apple aphid or another kind of insect that feeds on the sap of newer, soft, succulent growth.

They are easy to control or even ignore. You could take a hose and a nozzle and knock them off with a powerful, directed spray on the foliage. If you want to be more aggressive, you could use a soap and water mixture and do the same thing with a hose and applicator. If they really bother you, you could nuke them by applying the Bayer insecticide for trees and shrubs and apply it to the soil surrounding the roots. In my opinion that is overkill. See if they continued to be a problem or not. Aphids typically become less of a problem as temperatures get hotter.

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