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Avatar for architect1180
Jun 6, 2020 4:58 PM CST


There are strange white fluff particles on the leaves of our hydrangea bushes, and possibly also on the canes. They blow off easily in the wind, so they are not attached to the plant. We don't think they're the beginning of powdery mildew, but we're not sure. We're also wondering if perhaps we have a borer in the canes (see pictures). Can anyone take a look at these photos and let us know how we should deal with this if it is a problem?

Here's some background info:

We live in the Chicago suburbs. Last summer we planted these three small hydrangea bushes (white lacecap we think) in our yard...we got them as suckers from family. All three are on the southern side of the house, but one of them is shaded nicely by a nearby tree, and has grown larger than the other two. The other two are actually right on the southwestern corner of the house and are in full sun. These two looked sad throughout summer and fall, but the one in partial shade did a bit better and even produced a tiny bloom in fall. All three emerged with great zest this spring. So far they've seemed to be making great progress, but now we are worried that a bug or a disease is preparing to ruin everything!

Any advice out there would be greatly appreciated!

Thank you so much,

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Last edited by architect1180 Jun 6, 2020 5:00 PM Icon for preview
Avatar for luis_pr
Jun 6, 2020 7:25 PM CST
Name: Luis
Hurst, TX, U.S.A. (Zone 8a)
Azaleas Salvias Roses Plumerias Region: New Hampshire Hydrangeas
Hibiscus Region: Georgia Region: Florida Dog Lover Region: Texas
Welcome to NGA, Ron. It looks like mealy bugs or Cottony Maple Leaf Scale, a cousin of scale and common in late May to June.

I was communicating with someone who lives in New York State and she took similar leaf samples to her Agric Extension Office where they identified that pest as CML Scale. This type of scale is related to mealy bugs so anything you use against one of them can also be used against the other. If the infestation is still growing, Imidacloprid could help but if the pests have left (there is nothing inside the cottony home) then the insecticide may not do much since they "left the nest" already.

I personally would apply it once any way this year. But then I would start reapplying it next year about 1-2 months before this time of the year.

If you prefer a more organic solution, you could squish them by hand, release beneficial insects such as lady bugs (beneficial insects) or apply insecticidal soaps, Safer's Ultra Fine oil, etc .etc instead of using Imidacloprid. Do not use both, the insecticide and the beneficial insects, at the same time because the insecticide will kill the beneficial insects.

The canes are fine. The inside often disintegrates fast during winter and leaves the center hollow. Stems that do not leaf out by the end of May can be cut all the way down.
Last edited by luis_pr Jun 6, 2020 8:57 PM Icon for preview
Avatar for architect1180
Jun 8, 2020 12:09 PM CST

Thank you, Luis!

I will use the imidacloprid. When you say imidacloprid, should I be looking for that by name in the store, or is that an active ingredient in the pesticide I need? I did see it in a pesticide today at Menard's, but the label said that there was less than 1% of imidacloprid in the product. Is this what I'm looking for?

Thank you again for your help!
Avatar for luis_pr
Jun 8, 2020 1:52 PM CST
Name: Luis
Hurst, TX, U.S.A. (Zone 8a)
Azaleas Salvias Roses Plumerias Region: New Hampshire Hydrangeas
Hibiscus Region: Georgia Region: Florida Dog Lover Region: Texas
Correct, imidacloprid is the name of the active ingredient.
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