Dark brown foliage on Itoigawa Juniper

Hi everyone,

Could you please help me identifying this issue I am experiencing with the foliage of an Itoigawa juniper?

The foliage turned dark brown starting from the tips, then they die.
The problem is not localized in one single area of the tree.

Thinned and pruned (reduced by 30% of the foliar mass) in mid October.

4 weeks ago it has been treated 3 times (1 application once a week) with a white dormant oil in order to prevent an infestation of aphids I had on another plant (the affected one has been treated carefully separated from this plant).

No fertilization regimen.
No mites present (white sheet of paper test)
Temperatures from 43F-61F over the last weeks.
What is happening?

Thank you very much!
Leo

A couple of questions:

  • When did the browning begin? (Before or after the oil treatments?)
  • What kind of oil did you use?
  • Could you say a bit about the soil and recent repotting? My first guess is that the roots aren’t happy.

Thank you Jonas,

Sure:

  1. the browning started 1 week ago. 2 weeks after the treatment.
  2. paraffinic mineral oil 0.80% (8 g/l) + cypermethrin 0.005% (0.005g/l)
  3. it has been repotted 2 years ago in 33% Akadama, 33% kiryuzuna 33% pumice. Never touched, great growth till September.

The rootball has not been touched, the pot does not look like it is full of roots, percolation looks great. I think the only problem could be wet soil due to extremely rainy weather but the tree is shelted (it is not exposed to rain)

Is it a damage caused by the cold wind? (My logic is: since the tree has been thinned and junipers get strength from their foliage, cold tolerance could have been impaired)

Another doubt is: since dormant oil is a viscous liquid that works by obstructing the trachea of spiders, is it possible it fills the stomata stopping transpiration? Should I mist the foliage in order to wash it?

What are the actions you would take to deal with this?
Thank you,
Leo

Cold causes bronzing on junipers, but I’d expect that effect to be more evenly spread out with the sheltered areas staying green and the exposed parts turning brown. I’d need to see a photo of the whole tree to see if the pattern looks more like cold, chemical burn, or something else.

As for the oil treatment, many people have noted that junipers can turn brown after spraying oil, but I haven’t seen damage arise this time of year - I’m more used to seeing it after spraying oil in summer. I also don’t know if it’s OK to mix cypermethrin with oil - do you know if this is a safe combination for junipers?

Am also curious if cypermethrin is OK for junipers - did the label suggest it’s good for conifers?

1 Like

I believe this type of attack is due to fungi that are created by excessive moisture in the roots. I’ve seen it happen many times. The whole tree may eventually die.
I suppose you need a fungicide spray.
Junipers grow better when we leave them in dry soil and do not want special care and watering.

1 Like

Your soil mix is very moisture retentive even though it is draining freely! I think that is a high percentage of Akadama and Kyru for juniper that prefer drier conditions. If you water on a regular basis rather than when the soil mix has dried out then that would create an issue!
I too, would suspect root issues! I would reccomend allowing the soil to dry out before watering and when you water, water thoroughly. If you are already allowing the soil mix to dry before dewatering then i would suspect the treatment.
If the chemicals added were the issue i would suspect a more general response overall. They may have contributed to weakening the tree but I would experiment with allowing the tree to dry out more between watering. Check the moisture level of the substrate for dryness well below the surface before watering.
Hope these comments help and the tree improves.
I should add that university studies have shown that several varieties of juniper react poorly to dormant oil applied in the fall. For that reason i would also consider rinsing the tree as you suggested. Perhaps cover the soil when doing so!

Thank you all for the fantastic ideas provided during the discussion.
I have rinsined the tree covering the pot with plastic.
Your suggestion make me think it is more a root problem and I will let the rootball dry out more. This conclusion is derived from Jonas’ and Frank’s considerations on the localization of the browning areas.
Awfully here in Southern Europe we had more than a month of rain and trees were damp for most of the time (soil was wet for days even in the pots of the shelted trees).
I’d impair the tree’s health with additional chemicals for fungi right now (if you do not suggest I had better to treat the tree for fungi in this specific moment) but will consider that approach should the reaction spread overtime.

As far as cypermethrin is concerned, the product label (famous producer) was not suggesting to avoid the application on conifers, it referred to all types of garden plants including bonsai.
In light of the bad experience I am having now I do not suggest to give it a try!
Many thanks!
Leo

One further small tip if i may. When you encounter a lot of wet weather it will help to tip pots slightly on an angle to help them drain faster. I usually put a small stick under one side to raise the bottom unevenly! This helps to avoid accumulation of water inside at the bottom of the container.
I then follow up by reducing or holding off watering until the soil is drying out after the wet weather stops. I live in a marine climate that often has lengthy periods of rain.

1 Like

Here is another option for your consideration. When I hear cool weather and lots of rain I think fungus. I have been fighting Kabatina blight (Kabatina juniperi) on both a juniper and a cypress for a few years now. It looks very much like the damage on your Juniper and the timing is right (fall/early winter). I am confident in my own diagnosis as I can see the black fruiting bodies under low magnification with a binocular microscope. Now I know that not everyone has access to a mike, but you may be able to see the black spots with a magnifying glass. There is lots online about this fungus and if you think that it may be the culprit, you can try alternating Dithane and Thiomyl come early spring. This has definitely given me the best results. Good luck with your tree.

2 Likes

Attached please find 2 pictures of the Kabatina on my Juniper. One shows the detail and one shows the even distribution on the tree. Hope this helps.


1 Like

Thank you Bobby,

The information you shared helped a lot.
I took some time to observe the tree and the pattern looks exactly like the one on your juniper. The only difference is the color of the tips that are darker and brownish.
I have reviewed the comments posted by the community and got to the conclusion that I need to keep the tree drier but also need to fight any fungus possibly harming the tree or the roots.
Since the products you mentioned are not available in Europe, I got a systemic fungicide (80% Fosetyl-Al or Fosetyl-Aluminium) applied both misting the foliage and added to the water.
Hope this helps.
Additionally, I try to increase exposure to sunlight and restore the O2-H2O balance.

Best,
Leo

Hi everyone!
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.

Which fungicide?
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,
Leo

1 Like

Thanks for the information Leo! How did you end up identifying the pathogens?

Hi Jonas,

A great professional with a database of specific phatogens affecting junipers got to the Phomopsis track.
Then I had a part of the foliage tested by a regional lab to be fully sure of what I was dealing with.

Thank you for the kind help, the forum is a very useful tool in sharing ideas and knowledge!

Cheers

1 Like

That’s fantastic, thanks for sharing! Let us know how the treatment goes, am curious about the recovery process.