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Location: north Italy (Alps)

Recently I noticed something strange on my hortensia in my garden, probably a disease/infection or some kind of bug: some white pods.

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These pods appear soft to the touch and are only on the woody stems of the plant, so far I have seen none on the leaves. These pods are about 5mm in length. I noticed them a few days ago on a plant, however on that plant it is currently spreading/increasing and also starting to appear on other nearby hortensia, which is concerning to me.

What is this? Assuming this is harming the plant, how can I get rid of it?

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pazi__fisch
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You've got an infestation of Hydrangea scale insect; it's already quite advanced, especially if it's spreading to other plants,and will need treatment to control it. Organic pest sprays which contain fatty acids and/or pyrethrum will reduce the population, but will need to be reapplied - the best time to spray is towards end of June, but looking at your plant, I'd start treating it now. It would also be helpful to apply fertiliser to the plant to help it survive the attack. This link https://www.rhs.org.uk/biodiversity/hydrangea-scale gives more information on scale insect generally and also treatment methods - however, because it's a UK link, you may find the products mentioned have different names in your country. Not mentioned in the link is another control method I use - you'll need some disposable cloths and a bottle of methylated spirits or 70% alcohol. Slightly dampen a cloth with your chosen solution and rub that over the woody parts to wipe off the scale, including any attached to the fence, but do not use this method on the green shoots or foliage.

Bamboo
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  • I may be translating this wrong from Italian: I have a soapy solution based on potassium carbonate and vegetable oils (soft potassium soap?), which mixed with water I spray on my cherry tree to help against aphids. Would this help against this scale too, if sprayed on the plant? And why would you usually wait until end of June, and not spray once you find the scale? – pazi__fisch May 24 '22 at 08:47
  • its more effective to treat later in the season, when the young have hatched out because they are more vulnerable to sprays, but that's no reason not to remove those visible on hard woody parts as described in the answer. I'm not sure whether your existing solution would work. – Bamboo May 24 '22 at 19:04
  • Going to a garden center they recommended to spray the plants with a "white oil" solution, which they say should usually be done around February, while avoiding to get any/too much on the leaves. – pazi__fisch Jun 04 '22 at 07:39