AusBonsai

Hi guys,

For those of you growing banksia, have any of you noticed this on your branches?
I’ve noticed it on serrata, aemula and integrifolia.
It’s the dark area.

Any advice would be appreciated thank you.
Rory

Hi Rory, a bit more info might help with ID. Is it on the surface or go under the surface? Can it be rubbed off (like mildew)? Is the branch underneath sound & healthy?
Cheers, Frank.

Hi frank,

It’s very had to rub off. It is all around the branch not just surface.

It can be on the ends, along he branch or anywhere.
The branch ‘appears’ to be healthy otherwise and leaves seem fine, but I don’t have a good feeling about it

have they been given full sun and not over watered? i gave one to a friend, they got blackening on the trunk like this and soon perished unfortunately much like on JMs. If it's only on the tips perhaps cutting back as far as possible with sterilized cutters and adding iron chelate watered in then letting the soil dry out may help best of luck

The serrata and the integrifolia usually need watering every day, but over winter about every 2nd day.
I assure you they aren’t being overwatered. They are usually almost dry at the end of a full day sun. I’m worried but have no idea.
They don’t get a lot of sun over winter, but will be getting strong sun from a few weeks ago until winter next year.
I’m reluctant to cut back until they’re in full health and growth during spring.

Grant Bowie, I’d love to hear from you.

What you have there is a severe case of death.

Looks like the same kind of thing that happens to Acer palmatum (stems blackening) and that is usually caused by root rot not fungus. What are you feeding your Banksias Rory and what is your mix? Take them out of the pots and take a picture of the roots - close up if you can. It could be pythium too. (roots again)

Possibly a powdery mildew, treat with lime sulphur at recommended rate and keep in full sun from then on.

Grant

@ treeman. I love your sense of humour but I do appreciate the advice.

I have spent all morning looking very closely at the situation.
I actually think Grant is closest, mainly because the 2 integrifolia Banksias that were given the strongest and most sunniest positions over winter don’t have any sign of the problem.

However, I will take your advice Mike and check the roots of one of them.
The sun levels drop substantially in my backyard for about 6 weeks, down to only about 1 hour of sun right in the middle of the solstice, but then goes back to nearly all day sun at the ends of the 6week period.

As always, thank you so much Grant for your advice too.

Interestingly there are absolutely no signs of the problem on any of the marginata that I own. But they were also given a higher preference of sun though.

Rory wrote: @ treeman. I love your sense of humour but I do appreciate the advice.

I have spent all morning looking very closely at the situation.
I actually think Grant is closest, mainly because the 2 integrifolia Banksias that were given the strongest and most sunniest positions over winter don’t have any sign of the problem.

However, I will take your advice Mike and check the roots of one of them.
The sun levels drop substantially in my backyard for about 6 weeks, down to only about 1 hour of sun right in the middle of the solstice, but then goes back to nearly all day sun at the ends of the 6week period.

As always, thank you so much Grant for your advice too.

Interestingly there are absolutely no signs of the problem on any of the marginata that I own. But they were also given a higher preference of sun though.

If that's powdery mildew then I'm the Virgin Mary.

Maybe Mary,but certainly not a virgin
Wouldn't powdery mildew be on the leaves as well,I know Grant is more experienced than me,but it is not the powdery mildew I have seen before.

Beats me. But whatever it is, it has definitely affected the banksias more that were shaded for longer during winter.


Yeah it’s so weird, it doesn’t affect the foliage at all.
If it has only just appeared you can rub it really, really, really hard and it comes off.
But the thick blackish area won’t rub off if it has got hold. But it doesn’t appear to affect the foliage in any way.
I had cut back the ends about a month ago at night with a light after work and hadn’t really noticed the problem.

I should mention, that pic that I accidentally uploaded twice, shows an area that looks like an infected part, but that was just me taking off the base of one of the leaves to see inside it.

But the reason I say I think Grant is closer is that I think it’s external and not internal from a root related problem.
I’m only relatively new to banksia so I’m begging for others’ advice at this stage.

I wonder if these close ups help more.....

So I’ve done more researching, and noticed from a catalogued photo back on 28th April 2018 that it was actually on some of the lower branches of the serrata. The serrata is the one that has been mostly affected.
The two lower branches from the 28 April 2018 photo are still alive and the foliage is still healthy.

When you click on each attached pic below, you can then touch the photo, and select the middle white square and it will open even larger for better resolution tonsee it clearer.

Neil, if you’re reading this, I’d love to know what you think too.

I have absolutely no idea.

You can see in the first photo below that I’ve scratched off the stuff and it’s green underneath.

Yes that's better. It doesn't seem to be inside the stem yet. That's good!

I think I would look to Botrytis as a possible culprit for that.

Cut off all affected stems, move the plant to a windier place.

You could try a cinnamon spray if you want to go eco. Half a Lt of metho, a jar of cinnamon steeped overnight, then add half a Lt of water and some milk and spray.

Thanks Mike.

Its very slow to develop so I hope its something not as serious like that

Hi Rory,
I think what you have is Diplodia Tip Blight its caused by the fungus, Diplodia sapinea, (=Sphaeropsis sapinea).
Cheers
Kirky