I have a Blue Alps juniper that I repotted in March 2020. It was an aggressive repot, with lots of roots lost coming out of the nursery pot. I used a well-draining soil, but I did keep it in part shade and probably overwatered. Also, being mindful of the strength being in the foliage, I had let the foliage run last year and this year, with the result that a lot of it shades out certain portions of the tree.
Now I see about a quarter of the needles have dry white and brown spots on them. Also, it appears that about a quarter the new foliage tips have been dying and turning brown. Photo below. Foliage on the top looks much better than shaded foliage, so I’m guessing it should have been in full sun since at least June AND that I am watering too often. Also, I need to clean the tree for styling, which will open up air and allow more light in.
So, I can easily move to full sun, clean the tree, and let the soil dry like Ryan suggests frequently in his streams.
However, is there a treatment for the white and brown spots? Perhaps an anti-fungal? They scrape off easily by fingertip.
I’ve had to deal with mild / moderate scale on a few house plants. This looks like a pretty severe infestation. Given the way that scale attach themselves to plants I’m not sure if an insecticide is going to be effective against this pest. In my opinion this looks pretty bad, I don’t know if I would personally invest the time in salvaging this. For my house plants I removed most of the scale manually which is an extremely time intensive effort. Let us know how this pans out!
Brian, get a dual action insecticide. One that kills on contact and systemically, normally you can spray 14 days apart which should eradicate them. Do you have hard water in your area? I can’t be sure but it looks like you may also have mildew.
Jaded-Evan: I think it looks worse than it is. First of all, it is affecting about a third to half of the tree, not all of it. Second, the tree is an important one in my bonsai journey and trashing it is simply not an option. Third, I styled the tree before spraying (but after the photo I showed with the scale), which coincidentally removed a lot of the affected foliage.
Keith-in-UK: After styling I first applied Neem Oil (probably limited effectiveness on scale but supposedly also can help with fungi and other issues), and several hours later applied a systemic insecticide. Now that I think about it, the Neem Oil may act to slow the uptake of the systemic agent! Time will tell. Perhaps I’m biased now that I look at it, but it looks like already the white/brown covering (scale, I’m guessing) has been reduced. Although aggressively repotted in March, the tree seems to have recovered nicely with lots of new growth (although some was covered in scale and a small amount on some tips had browned completely and died).
My hope is that with the treatments, new location in bright sunlight, better air flow and light penetration everywhere due to removed foliage, that it can recover quickly.
