"Scale" identified on Eastern Hemlocks - Ask Extension
Trees are in Rocky River Ohio. Patches of what has been identified (at local nursery) as Scale. How and when do I treat the scale before it gets wo...
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"Scale" identified on Eastern Hemlocks #852916
Asked October 12, 2023, 7:06 AM EDT
Trees are in Rocky River Ohio. Patches of what has been identified (at local nursery) as Scale. How and when do I treat the scale before it gets worse?
Cuyahoga County Ohio
Expert Response
Thanks for contacting Ask Extension
Did the local nursey person identify what type of scale was identified? There are primarily 2 types that can feed on ornamentals both soft and hard shell scale. They require a different approach to treatment.
Horticulture oil in the dormant season can be one of the most effective tools for getting rid of scales with a minimal impact on natural enemies. Unfortunately only 7 of the 22 kinds of scales listed.
Armored scales. These insects spend most of their lives covered with a waxy shell that cannot be penetrated by many insecticides. The only times they are not under their shells are when they hatch from eggs and when the males fly to mate with females. Newly hatched scales are easily killed by insecticides. Products that can to kill scales with a minimal impact on the natural enemies include a summer rate of horticultural oil, or an insect growth regulator, like pyriproxifen or buprofizen. Timing of crawler hatch will vary with each species of armored scale.
Soft scales, like calico and tuliptree scale, and felted scales like European elm scales are not covered with a waxy shell and insert their wire like mouths directly in the plant’s vascular tissue to sip from its circulatory system. As such, they produce copious amounts of liquid excrement called honeydew that can attract stinging insects. This sticky liquid becomes contaminated with black sooty mold that turns plants black and crusty. Heavy infestations can ruin the finish on a parked car, and make the turf below a sticky crinkly mess. Oil does NOT kill these scale insects after they have settled down to feed and coat themselves with honeydew. Insecticidal soap does a better job of controlling these scales and insect growth regulators like pyriproxifen and buprofizen work even better. The trick is to apply these products soon after the crawlers settle. Many of these scales like calico and European Elm scale hatch from eggs in late May and spend the summer on leaves and return to the trunks in the fall. Other species like tuliptree scale will be more susceptible to insecticides when eggs hatch into the crawling stage during late summer.
When dealing with soft scale species like lecanium scales a systemic treatment can be used without relying on a broadcast spray Imidacloprid is frequently used and available at local nurseries. Timing is important when choosing a systemic product. mid October -November and again for a spring treatment April-May is the window for insect control.
Below are a few extension sites that will give you more information. You might go back to the local nursery with a sample of the tree branch that is currently infected and ask for more detail in identifying the scale type. This will lead you to a decision on how to best treat the trees.
https://bygl.osu.edu/node/1803#:~:text=Scrub%20it%20Away.,in%20reducing%20burgeoning%20scale%20populations.
https://www.purduelandscapereport.org/article/dormant-applications-horticultural-oil-can-help-control-troublesome-pests/
https://entomology.ca.uky.edu/ef430
Did the local nursey person identify what type of scale was identified? There are primarily 2 types that can feed on ornamentals both soft and hard shell scale. They require a different approach to treatment.
Horticulture oil in the dormant season can be one of the most effective tools for getting rid of scales with a minimal impact on natural enemies. Unfortunately only 7 of the 22 kinds of scales listed.
Armored scales. These insects spend most of their lives covered with a waxy shell that cannot be penetrated by many insecticides. The only times they are not under their shells are when they hatch from eggs and when the males fly to mate with females. Newly hatched scales are easily killed by insecticides. Products that can to kill scales with a minimal impact on the natural enemies include a summer rate of horticultural oil, or an insect growth regulator, like pyriproxifen or buprofizen. Timing of crawler hatch will vary with each species of armored scale.
Soft scales, like calico and tuliptree scale, and felted scales like European elm scales are not covered with a waxy shell and insert their wire like mouths directly in the plant’s vascular tissue to sip from its circulatory system. As such, they produce copious amounts of liquid excrement called honeydew that can attract stinging insects. This sticky liquid becomes contaminated with black sooty mold that turns plants black and crusty. Heavy infestations can ruin the finish on a parked car, and make the turf below a sticky crinkly mess. Oil does NOT kill these scale insects after they have settled down to feed and coat themselves with honeydew. Insecticidal soap does a better job of controlling these scales and insect growth regulators like pyriproxifen and buprofizen work even better. The trick is to apply these products soon after the crawlers settle. Many of these scales like calico and European Elm scale hatch from eggs in late May and spend the summer on leaves and return to the trunks in the fall. Other species like tuliptree scale will be more susceptible to insecticides when eggs hatch into the crawling stage during late summer.
When dealing with soft scale species like lecanium scales a systemic treatment can be used without relying on a broadcast spray Imidacloprid is frequently used and available at local nurseries. Timing is important when choosing a systemic product. mid October -November and again for a spring treatment April-May is the window for insect control.
Below are a few extension sites that will give you more information. You might go back to the local nursery with a sample of the tree branch that is currently infected and ask for more detail in identifying the scale type. This will lead you to a decision on how to best treat the trees.
https://bygl.osu.edu/node/1803#:~:text=Scrub%20it%20Away.,in%20reducing%20burgeoning%20scale%20populations.
https://www.purduelandscapereport.org/article/dormant-applications-horticultural-oil-can-help-control-troublesome-pests/
https://entomology.ca.uky.edu/ef430
Thank you so much. Every nursery AND the arborist said simply "scale"! I will take the samples back to another nursery.
