Magnolia scale - Ask Extension
I have an approx. 70 year old saucer magnolia tree . I have an arborist fertilize the tree once yearly and i have the tree pruned or thinned to open u...
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Magnolia scale #876911
Asked July 12, 2024, 1:42 AM EDT
I have an approx. 70 year old saucer magnolia tree . I have an arborist fertilize the tree once yearly and i have the tree pruned or thinned to open up the interior of the tree. Last year for the first time in 45 years , a small 1-2 branch area of the tree had magnolia scale. A tree service came and applied a treatment in mid august and a second application 2 weeks later. All seemed good. This year the younger branches of the tree are all covered in the prototypical white mound like patches . Of course the excretions from the scale hs covered my sidewalk and porch. I dont know if i can trust the people who treated my tree last year since it was an epic fail when it came to controlling the scale infestation. The tree is about 30 foot tall and its crown spreads about 30 feet or so. Is there a treatment I can apply myself ? If so would it interfere with anything the commercial service might use. Please help. This tree provides the most magnificent shade . Along with the 30 year old cherry tree my fromt yard is completely shaded.
Franklin County Ohio
Expert Response
Hi Susan! How frustrating! Since I don't know exactly what the people did last year, let me tell you how magnolia scale should be treated:
when it's just a small area (like the one or two branches you had last year), the branches can be pruned off and destroyed. But now it has progressed to more of an issue. So what to do:
In late August, you can use a horticultural oil that you thoroughly spray to cover the leaves, stems and branches where you see the scale. The oil MUST cover on crawlers (baby scale insects).
In October-November, you would spray a dormant oil in the same places. This has to be reapplied after freezing nights are finished but before the buds open as the oil will damage the opening buds.
Another option, probably the better option, is in early May use a soil drench insecticide of imidacloprid or dinotefuran. Check with your local nursery/plant store to see what brand names have these chemicals. You pour them on the ground, around the tree root area and water it in to make sure the roots take up the chemical. Keep in mind that this insecticide is non-selective on what it kills so be careful if bees, butterflies and other beneficial insects are in the area.
IMPORTANT: WHEN USING CHEMICALS, THE LABEL IS THE LAW. (I'm not yelling at you; I just want to make sure you understand that you MUST read the label and use it only as intended.) Wear PPE: gloves, long sleeves & pants, shoes (not sandals or flip flops), eye protection and even the mask that we all have now.
When having anyone treat your trees or inspect them or do anything to your trees, please use a certified arborist. You can find one at Find an Arborist (treesaregood.org) .
Let us know if you have any other questions. Good luck with your trees!
when it's just a small area (like the one or two branches you had last year), the branches can be pruned off and destroyed. But now it has progressed to more of an issue. So what to do:
In late August, you can use a horticultural oil that you thoroughly spray to cover the leaves, stems and branches where you see the scale. The oil MUST cover on crawlers (baby scale insects).
In October-November, you would spray a dormant oil in the same places. This has to be reapplied after freezing nights are finished but before the buds open as the oil will damage the opening buds.
Another option, probably the better option, is in early May use a soil drench insecticide of imidacloprid or dinotefuran. Check with your local nursery/plant store to see what brand names have these chemicals. You pour them on the ground, around the tree root area and water it in to make sure the roots take up the chemical. Keep in mind that this insecticide is non-selective on what it kills so be careful if bees, butterflies and other beneficial insects are in the area.
IMPORTANT: WHEN USING CHEMICALS, THE LABEL IS THE LAW. (I'm not yelling at you; I just want to make sure you understand that you MUST read the label and use it only as intended.) Wear PPE: gloves, long sleeves & pants, shoes (not sandals or flip flops), eye protection and even the mask that we all have now.
When having anyone treat your trees or inspect them or do anything to your trees, please use a certified arborist. You can find one at Find an Arborist (treesaregood.org) .
Let us know if you have any other questions. Good luck with your trees!
Thank you. Clarification please, according to the OSU penology calendar and others Magnolia scale eggs are hatching now or at least beginning to. Should I really wait til August to treat or should I consider a first application in a week or so.
Thanks for your information I just want to be sure I am understanding the phenology info correctly.
Susan
Hi Susan! The female lays her eggs over a long time. They begin hatching in early August all the way through mid-September. You will have to do repeated sprays during this time period. The crawlers will start moving around until they find a place to overwinter. By waiting, you a week or two, you will get more of the crawlers than starting now. You'll still have to spray again later in August and into September.
