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White organism on bushes (scale?) #874632

Asked June 25, 2024, 12:48 PM EDT

These bushes are at least 25 years old. Last autumn, I noticed white pests on the undersides of the leaves, especially on the branches close to the house. I think the photos show different stages of the pest. They are also badly affecting my holly bushes, turning the leaves black. (I will follow up with a post of photos of the holly.) In between the infested green bushes and the holly, is a beautiful Japanese Maple, which doesn’t seem to be affected. A Dogwood is also close by. I am worried the pests will continue to spread all over the garden. Can you recommend what I can use to get rid of them? Should it be a chemical or can parasitic wasps be introduced? I don’t know anything about pest control as the garden had been quite healthy. I have tried to stay organic.

Oakland County Michigan

Expert Response

Hello Marie,

This white pest on your yews are Taxus mealybugs. They are sap feeders and the honeydew that they excrete and drips onto the plant attracts sooty mold to grow and the plant and anything below it will turn black.

They can be treated by applying a horticultural oil (active ingredient mineral-based paraffin or olefin) or and insecticidal soap (active ingredient is potassium salts of fatty acids). There are chemical options also. Read more here: https://plant-pest-advisory.rutgers.edu/landscape-pest-notes-some-late-spring-insects-part-2/

Read more information about mealybugs here: https://horticultureforhomegardeners.ca/2021/03/01/mealybug-damage-to-yews/

Often stressed plants attract pests. To help them resist, ensure that the plants are adequately watered, but not overwatered. Read about Yews here: https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=260418&isprofile=1&gen=Taxus

When using chemicals on plants, read the plant to ensure that the chemical can be used on that specific plant to treat that specific problem. Follow the directions on proper application.

Thank you for contacting Ask Extension.


An Ask Extension Expert Replied June 26, 2024, 4:55 PM EDT

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