Hello, Jeff! Thank you for your excellent question to AskExtension/Ask a Master Gardener and thank you especially for the great photograph and comprehensive information. I think I can help you with your question about treating your cherry trees for scale.

A little background information: I am a Master Gardener in Hamilton County Ohio and, along with a large group of others, I volunteer my time to answer questions from gardeners and homeowners across the state. To be certain that my response is current and accurate I have consulted several research-based sites; the links to the best of those are embedded in the response and/or included in the list of resources. If you need clarification or additional information (or if you feel that I should escalate your question) you can reach me directly by responding to this email. I would be delighted to hear from you and would love to know if my response was helpful to you. Completing the survey at the very end is always helpful to our group.

You did some fantastic research, and I agree with you that your cherry trees are infested with scale. Our group receives many questions about scale at this time of year. Whether your tree has Kuno scale or another type is not possible to tell from a photograph. (Hold on … good news coming!) The photo closely resembles those of Kuno scale, although I have not been able to verify Kuno in Ohio; it is more common on the west coast. It is possible that this is the more common European Fruit Lecanium, (scale) or another type of soft scale that is common in Ohio. The good news is that you would use the same treatment for most soft scales. If you want a definitive identification of the scale on your cherry trees, you could send a sample to the Plant & Pest Diagnostic Clinic (PPDC); for a fee of about $20 they will analyze your sample. Details about how to send a sample can be found here. BTW, we do not receive any profit should you choose to use the PPDC.

Regardless of the variety, scale can harm trees over time. It is likely that scale has been present in your trees prior to detection of an infestation; they are good at concealing themselves! If you want to ensure the best result, you might choose to hire a certified arborist. Please be sure they are certified; this article will help. An arborist should help you create a treatment plan. You could also devise your own plan. The basics: During the spring and early to mid-summer, while the “crawlers” are active you will want to remove and destroy as many as possible. You can use jets of water and brushes to dislodge as many as you can reach; they then become susceptible to predators and desiccation. Each one you remove is one less that will reproduce. Follow up with a horticultural soap, such as Neem oil, to spray as much of the foliage and branches, upper and lower sides, as possible. (Be sure to follow all package directions and use appropriate personal protective gear.) This destroys their protective coating. Again, each one destroyed is one less that will reproduce. One note about horticultural oils: apply on a cloudy day or late in the evening to prevent sun scald of leaves (sort of like sun burn for plants.). An arborist may be able to complete these tasks for you if you desire. Finally, you can use a dormant oil after leaf drop in the fall or before leaf bud in the spring. You can also have a professional apply a systemic insecticide or an IGR (insect growth regulator) at the proper times. This article gives details about management practices. See the Management section and click on the tabs. [A personal note: our Star Magnolia trees suffered a scale infestation several years back. We applied mechanical & physical removal techniques then had a professional apply systemic pesticides. The trees are doing well. We continue to monitor them for scale.]

An important note: my response is predicated on an assumption that this is a soft scale. This timely article from the BYGL (Buckeye Yard & Garden online) regarding scale at this time of year demonstrates how to tell if you are dealing with soft scale as well as other pertinent information. Should you discover an armored scale, please write back and I will escalate your problem. You might also want to check out information about scale from University of Maryland Extension and in this article from NC State Extension. Understanding their life cycle is “key to managing them effectively”.

Jeff, I wish you the best of luck in dealing with scale in your cherry trees. Please feel free to contact me any time if I can be of further help.

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Resources about Scale Insects

Introduction to Scale Insects https://extension.umd.edu/resource/introduction-scale-insects/

Sticky Drippy Maples https://bygl.osu.edu/index.php/node/2131

Check Fruit Trees for Scale Pests https://growingsmallfarms.ces.ncsu.edu/2016/02/check-fruit-trees-for-scale-pests/

Pest and Plant Diagnostic Clinic https://ppdc.osu.edu/submit-sample

How to Hire an Arborist https://ohioline.osu.edu/factsheet/hyg-1032

You are very welcome! Please lmk if I can be of any further help. 

PS ... I meant to mention in my previous response that insecticides other than horticultural oils are not recommended for use on crawlers because insecticides are mostly ineffective on crawlers and are more likely to harm beneficial insects, including those that prey on scale. You might already know that from your research! :)