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Diagnosis needed for my Juniper and Chamaecyparis


Unfortunately both my conifers which I just repotted in 18cm diameter pots and kept on my balcony in a shaded position appear to be affected by a somehow similar fungal disease.

The juniper (1st picture) seems to be at the early stages of the disease, while the chamaecyparis, together with the white layer on the base of the plant that you see in the picture, also has around 15% of the cones which turned brown-ish.

The products I have at my disposal are Fosetyl-Al based fungicide, Neem oil and the usual green soap.

Could you please help me with the diagnosis of the diseases, together with advising me on which products to use to fight them?

Thank you in advance.


  • FairygirlFairygirl Posts: 53,966
    How are they planted, and in what type of soil? What is the drainage like?

    18cm pots are tiny - conifers of any kind won't be very happy in them long term, especially on a balcony where they could be getting wind damage as well.
    It's a place where beautiful isn't enough of a word....

    I live in west central Scotland - not where that photo is...
  • Hello Fairygirl,

    Thank you very much for your support.

    I'll then add a few more facts:
    • I recently bought them from a plant nursery and repotted them by using only soil for acid-loving plants. I know conifers like large pots, and plan to put them in larger ones perhaps next year.
    • Perhaps I may be leaning towards too much water compared to too little, as I water them again once the superficial layer of soil is still slightly damp, but I always remove the water from their dish
    • I added some NPK 13:5:9 organic fertilizer a couple of weeks ago as specified by the product instructions
    • On my balcony (I live in Rome, current temperatures ranging from 20/25 degrees to 10/15 at night) the wind is neither too strong nor completely absent
    Some things I could do are:
    • Bring the plants inside my house (no wind but still no direct sunlight) 
    • Take them to the hallway of the floor of my flat (no wind but they would get way more direct sunlight, as the exposure is different)

  • FairygirlFairygirl Posts: 53,966
    I wouldn't bring them inside - that's unlikely to help.
    I think they might be too wet then. It did look like that from the photos, but it's often hard to tell. They don't need to be permanently damp, especially when small. Good airflow is important too,  as it helps plants to avoid any pests and diseases. 
    Make sure they are off the ground too. I'm never keen on trays under plants, as it's harder to prevent them getting too wet, but I can see that it helps in a very dry environment. 
    When potting them, it's also important that the drainage holes aren't able to get blocked. 
    Be careful not to give them a lot of food either. If they've just been repotted, they really won't need anything else, as the compost will have enough nutrients for them for a good while.  :)
    Like many plants, a humid atmosphere can encourage insect activity - and there can be lots on the compost itself. I wouldn't worry too much, unless you see an infestation of some kind. Some conifers can be a bit susceptible to the odd thing.
    It's a place where beautiful isn't enough of a word....

    I live in west central Scotland - not where that photo is...
  • Hello Fairygirl,

    Thank you, I'll be following your advice then.

    The final question: do you have any idea if there may be a specific fungus or pest behind the white spots on the cones of the juniper as well as the white layer at the base of the chamaecyparis and itsbrown-ish cones?
  • FairygirlFairygirl Posts: 53,966
    edited May 2020
    It may be a bit of mildew, which can be caused by poor airflow, or over /under watering.
    Did you make sire you potted them at the same depth they were in their initial pots? 

    There are some pests and diseases that conifers can get, but I have no experience of them as they grow so well here without any bother. It could even be just some mould from the compost, which is often present. 

    Someone else may be able to advise on that though, or you could check out the RHS guides for conifers  :)
    It's a place where beautiful isn't enough of a word....

    I live in west central Scotland - not where that photo is...
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