Oystershell scale on aspen trees

Asked April 17, 2019, 11:00 AM EDT

Aspen tree trunks and branches have what appears to be oystershell scale (looked on internet to ID). The trees are in our yard as ornamentals, are about 8 years old and up to 25' tall. What is the best control method at this time of year? The trees are just barely starting to bud at this time. Can send pictures if necessary.

Goshen County Wyoming

3 Responses

Oystershell scale is pretty common on aspen in Wyoming. A tree that large is past the point where hand removal of the scale is possible or practical. You can try horticultural oil treatments or to smother the new generation of scale insects that will hatch from eggs hidden under the waxy scales formed by their mothers bodies. Or you could apply a spray application of insecticide timed to kill the newly hatched scales before they cover themselves with wax. Without proper equipment to spray a tree this will be difficult and expose you and non-target creatures to the insecticide.

If it was my tree, I would try Ortho Tree and Shrub Insect Control Granules. It is a homeowner version product with dinoterfuran as the active ingredient. It is a systemic applied to the root zone of the tree as granules and then watered in to the soil. Dinotefuran, unlike some other systemic insecticides has proven to be very effective against hard scales like oystershell in the commercial insecticides Zylam and Safari. Prof. Cranshaw from CSU has a good fact sheet on this pest here https://extension.colostate.edu/topic-areas/insects/oystershell-scale-5-513/

Thanks. Having some trouble finding the product you mentioned. Think it may be available on Amazon.

Yes it is available online and you can check with your local stores that carry Ortho products. They may be able to order it in. It is used extensively in areas with emerald ash borer to protect trees but may not be sold in this region.