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After inquiring at a local nursery in the west of Ireland, I planted in a handful of Rhododendrons last year, to see how they might tolerate my soil. They seem to be thriving pretty well, But I noticed what look like bites taken out of some leaves.

See photo.
Any suspects?

Rhododendron, what look like bites taken out of some leaves.

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    Did you check the leaves, especially the undersides? – Stephie May 16 '18 at 19:33
  • You have adult beetles eating the leaves. You need to look at the roots, shallow...to see what the larvae are doing. They will kill Rhododendrons at the roots. You've got too many growies at the base of this Rhododendron, and I see way too deep of a mulch layer beneath. Rhododendrons have shallow root systems and a couple of inches of mulch will 'smother' the roots. Stress your shrub. Allow insects to take over. Too much great habitat for beetles and slugs and whatever. Pull the mulch away from the trunk and under the canopy, ASAP. Pull those weeds. Take a picture of what you find... – stormy May 17 '18 at 2:07
  • Thanks @Stephie, nothing biological on the undersides or anywhere that I can see nearby. But as noted below, it has not gotten worse nor has it appeared on other Rhododendrons in my property, so it may be that no remedial action is required on this count. – MikeRoger Jun 14 '18 at 13:58
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Looks like vine weevil damage, judging by the notches at the leaf edges, but that's much more of a problem with plants in pots than in the ground usually. If the damage is on other plants too, you may need to use a nematode solution, but if it doesn't get worse, then you might not need to. Nematode solutions are temperature dependent so can only be used at certain times of year, and are watered on as a soil drench. I think the minimum temperature for use is 18 deg C, but that information is on the pack; Nemesys Vine Weevil killer is available via Amazon and other garden supplies retailers on line.

However, its hard to work out what your rhododendron is planted in - there appears to be quite a pile of something or other directly behind and around it (old grass clippings? mulch of some sort?). Whatever that is, it's way too high and looks as if its probably against the base of the plant, which it shouldn't be, so clear away whatever it is, it won't be helping, and keep the mainstem of the plant at the base clear of anything like that to prevent other problems arising. It's also possible some of the leaf damage is caused by slugs, all that material piled up will encourage those by creating a nice damp environment for them. A minimal, sparing sprinkle of rainproof slug pellets (Erazer are rainproof) on the soil once the excess material has been removed will take care of the slugs.

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  • Thanks @Bamboo for that very useful feedback. Yes it has not gotten worse nor has it appeared on other Rhododendrons in my property that I have noticed. But I will be on alert for nematodes just in case. In the west of Ireland, 18C can be difficult to achieve on any consistent basis, even in high summer, but as you say, it may be that no anti-nematode action is required. – MikeRoger Jun 14 '18 at 13:51
  • On the surroundings, yes grass clippings, mea culpa. My ill informed and time-poor answer to weeds growing near and competing with my new plantings. I am sure there are better solutions, but with 4 offspring, full time paid position, active volunteering life added to non-nuclear family commitments and activities plus indoor household maintenance etc., the poor garden is almost last on a long list of priorities :) – MikeRoger Jun 14 '18 at 13:52

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