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Is this Rhododendron dying? Please help me save it...

Hi everyone,

I have a rhododendron in the garden, the plant is quite old, at least 40 years old, and is growing in Hamburg (the type of soil in my garden is called "Heideboden"). It was doing well when we first moved in, but two years ago, rhododendron cycadas started to appear. We suspect that one of the plants we got on sale and planted near it had them.

Recently, the leaves of the rhododendron have become more and more yellow (2, 5) and have developed rust (4). Today, I also noticed that some of the leaves have white stuff on them (1). I have picked some of the affected leaves to show the problems. Photo:

Every year in the spring and autumn, I picked off the brown buds from the plant and threw them away somewhere else. I also began adding rhododendron fertilizer twice a year, in the spring and autumn. Last year, I even added fresh rhododendron earth all around it.

I have tried killing off the rhododendron cycadas with insecticide, but it didn't work. This year, I plan to dig up the soil in a week or two to kill some of the larvae, and then add diatomaceous earth and mulch to prevent them from crawling out. I am also considering using nematodes and Zikadex, although I'm not sure yet.

I would appreciate any advice on whether my rhododendron can be saved and what steps I can take to improve its health. Thank you in advance!

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