Help on severe Dothistroma case on Mugo Pine

[Dystopik]

I have a severe Dothistroma case on two of my Mugo pines. I have acquired them in may from as a pre-bonsai nursery material (from specialised bonsai nursery in Europe).
This one in the picture was initially weak looking when arrived, but over the growing season actually improved.
End of August, beginning of August, Dothistroma infection became very sudden apparent on all needles: red colour from mid needle, clear banding and black dots. All needle are infected. Still have some green at the basis on needles.
Tree is still forming new buds, even on very old wood.
I applied copper based fungicide, but I know I was way too late, as this is not curing affected needles. It was more in hope not to infect my other mugos.

Any advice? Can I still save this tree? I am in Europe so none of the fungicide recommended online are not available in EU.
Any systemic fungicide for this issue that might work on pine? Are systemic fungicides ok for pines, considering they have and need healthy mycelium/mychorriza on the roots?

 

[RoadManDenDron]

hopefully more experienced members will chime in, most of them are in different time zones to us so it may be later this evening.

I have never experienced this before but I have applied systemic fungicide to my pines, I put the pot in a bag to cover the soil whilst I spray, remove bag afterwards and do what I can to keep the tree out of the rain

if you have dry days ahead I would be likely to preventative spray your other mugos/pines but I would not want to shelter them in the same place as these ones.

 

[JeffS73]

Dystopik, I feel for you! That does look pretty bad, and with no candles emerging, there are no new needles to come to the rescue.

Normally I would say remove the infected needles, but I wouldn't do that in this case. If a needle goes black, it will be sporulating, cut that off just behind the black bit.

Can you get copper fungicide to spray on? Sometimes it is sold as a fertiliser as a 'workaround the rules'. This is the best defense against dothistroma spreading further. I've seen no evidence that systemics work.

Apart from that, root health is vital. Do not over water, keep sheltered from rain or mist. Only very weak fertiliser, if any at all.

Cross your fingers for Spring, perhaps complain to the vendor. In the UK a nursery selling infected plants could have its stock destroyed by the authorities.

Best of luck!

 

[Shibui]

I cannot see the banding I associate with dothistroma. I would usually put solid browning of needle ends down to dehydration but accept that you have noted the symptoms. In any case, copper fungicide will help halt the infection for this year. Just make sure watering is not the underlying cause here.
The tree is still healthy enough to get through and survive though it will obviously take a couple of years to regain lost strength.

You are correct that damaged needles cannot recover. Treatment is simply to halt the spread of any fungal infection for this season.
In spring new growth should emerge as usual. Dothistroma does not infect the tree itself and emerge in following seasons. It infects emerging needles in spring each year so not too difficult to control with preventative treatments through spring to protect fresh needles from infection. Use your copper spray regularly from when candles start to open until needles are hardened. I'd probably treat all pinus sp for the next couple of years at least to make sure it is not still around.
Copper should be nearly as effective as systemic if applied properly and regularly. Systemic is only slightly better because it travels to all needles which helps mitigate some sloppy application.

 

[Dystopik]

Thank you guys so much for the info.
Here are some other photos from my another mugo pine, that seems to cope better. It is visible the orange/brown needle tips, thin dark bands, white specs and "ashy/burnt" look on needle ends.
I only have 3 mugo pines, all bought this may from same bonsai nursery. All very healthy and strong.
If this is not Dothistroma, is Mycosphaerella, brown spot needle blight. I see they are very similar.

I have applied copper hydroxide fungicide twice (2 weeks apart) on my 3 mugos (they are unevenly affected).

The question is: Should I trim the affected needles? Removing the brown part of each needle and only keep the green part? This might help reducing the fruiting bodies on the fungus perhaps? I know cutting needle is done for black pine, so I am thinking it will not impact negatively more than the fungus itself.
What do you think?

 

[Shibui]

Cutting the brown sections should not negatively affect the trees as the brown parts are already dead and not feeding the tree.

 

[Paradox]

this lonk talks about this fungus and how to treat

Dothistroma needle blight

How to identify Dothistroma needle blight

extension.umn.edu

What Causes Needle Blight & Cast of Pines | Davey Tree

Brown spot needle blight causes straw-colored to light brown spots on needles in late summer or early fall. Spots emerge, killing most of the needle and causing premature defoliation the following summer. To manage brown spot needle blight, apply a protective fungicide in early spring.

www.davey.com

 

[Dystopik]

Very useful information. Thank you. I will cut off the dead, infected ends of needles to hopefully remove as much of the source for more spores.

I have also found it on a few needles of Cedar of lebanon (image bellow) that were closer to the pines. Turns out cedars, larches, some spruces are also susceptible for Dothistroma. I have now spayed the cedars too with copper fungicide.

 

[SgtPilko]

As this is clearly a serious case that is holding the tree back health-wise and prevents you from doing any work, I would hit all trees with a systemic fungicide as well as your copper in autumn and again in spring, or on those timetables mentioned in above links. I am not sure exactly which one works best on this infection, or what is available near you, you might find something ok off the shelf in the garden centre but they tend to be weak at least here in UK. You could try looking for something more "agricultural" with the active ingredients Fosetyl or Methyl Thiophanate. I have only used them preventatively or on other fungus types (effective!) Not your specific case.