Just a quick update with the information I have collected so far.
I am sharing this information just for anyone fighting with this issue (see pictures above).
The problem is related to a fungus, specifically the Phomopsis Juniperovora, that, together with Kabatina, are the 2 main pathogens affecting junipers with tip blight.
The fungus gets inside cuts in the bark and reaches the sap from spring to fall and can affect the foliage later on, from early to mid winter in mild climates.
Main symptoms: browning tips of the foliage that starts with dark brown (at times purple) spots leading to dead tips in approx 4/5 days. The infection moves from the green tips inward.
This fungus spreads FAST. Consider that in 2 weeks the plant lost 20% of its foliar mass. It gets easily from the first branches to the apex in a week and the infection expands using water as a vehicle (so, avoid exposure to rain and do not mist the foliage if you suspect a fungus problem).
The infestation of the fungus is deadly for the plant if left untreated.
Control of the infection and cure: the fungus reproduction relies on the spores located at the base of each lesion (the ones mentioned by Bobby). Hence, cutting the damaged tissue away helps in controlling the infection. It does not solve the issue but you can buy time and find the right chemical for the treatment. The main solution, in fact, is the use of fungicides.
I have been suggested to treat the plant with the following molecules:
- mancozeb (contact: misting the foliage)
- methyl thiophanate (systemic: irrigation)
- difenconazole (systemic: irrigation)
According to the information I collected, the first molecule is strictly regulated in many countries in Europe and can be applied only by professional gardeners with an appropriate license (it seems to be due to cancer-related studies and safety issues). The second molecule is strongly effective but, in Europe, it still needs to be applied by a licensed professional and it is difficult to obtain it in some countries.
In my case, difeconazole works. It is commercially available, systemic, environmentally and medically safe.
Please note that the information provided is based on articles available online and talks I had with professional gardeners and it is not the result of any scientific research I prepared on the pathogen or the molecules.
I hope you find this information helpful.
I will keep you posted.
Many thanks and cheers,