Scale (cottony maple?) attacking preziosas. How hard can I prune?

jillyluis(6A)June 20, 2011

I have three beautiful preziosa hydragneas that I love. I believe they were planted eight years ago, and they are quite large, about 5 x 4 feet. They are being attacked by scale: I'm pretty sure it is cottony maple scale. My husband sprayed neem oil a couple of weeks ago, and it seems like only about 10% are left....but 10% of thousands of scale is still quite a bit. The hydrangeas had a tough time recently: I don't know if it was the drought last summer (I tried handwatering, but doubt I kept up) or the tough winter we had, but I have a lot of branches that aren't dead but don't have any foliage either. Also, I cut off some of the branches heavily infested by scale, so now the bushes look terrible.

My essential question, is how hard can I prune the bushes without killing them altogether? They are just too big, and I don't see how I can get all the scale with all the leaf cover they have right now. I can live without flowers next year, but I really really really hate scale. I've thought about ripping these out and replacing them, but that seems a bit aggressive at this point.

Any other suggestions would be helpful! There is a lot of conflicting information on the web about when to treat etc. We don't in general use pesticides (neem oil or horticultural soap is about as aggressive as I'd like to get)

Thank you!

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I'm zone 6A if that helps.

    Bookmark   June 20, 2011 at 9:13AM
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I'd need to see photos to confirm the problem before I made any suggestions.

Scale is a difficult garden pest to control and if the infestation is severe enough, the recommendation is to remove and destroy the plant. Some systemics may be effective but before going further, I'd want to see how bad the situation was :-)

    Bookmark   June 20, 2011 at 11:58AM
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Here are some not so great pictures...I took them with my phone, so the closeups are out of focus. Is there anything in particular that would be helpful to see? We have a digital camera....somewhere :)
Thanks a bunch!

    Bookmark   June 21, 2011 at 10:30AM
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It's a cottony maple scale, indeed, and for the last 2-3 years we have a severe infestation here in New England.
Due to their life cycle they are very hard to get rid of completely.
As far as I know (from my own experience) only Safari (Dinotefuran) if applied twice a year (at the right time) AND for two years on a row could give you complete freedom from the beast.

Re: as far as hydrangeas concerns. If you cut them to the ground now then by the next year you'll have a nice healthy rejuvenated shrubs.

P.S. Every leaf and branch from infected plants must be burned, not composted.

    Bookmark   June 27, 2011 at 1:56PM
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