Ravenala madagascariensis (Traveller's palm) fungal problems -- help!

[harleyb]

Hi all,

I've been growing Ravenala madagascariensis here in NZ from seed in a greenhouse for a couple of years and have had ongoing problems with fungal attack. A few months ago I thought I was getting on top of the problem by cutting off the affected leaves and then spraying with Physan 20 plus a systemic fungicide (Yates Fungus Fighter, active ingredients trifloxystrobin and tebuconazole), but despite a slight improvement early on, the fungus has since come back and gone through all my young plants, leaving them damaged and unsaleable. Very frustrating! 😞

I don't know what the fungus is. It starts as brown mottling along the leaf margins, then gradually takes over the entire affected leaf giving it a freckled appearance. Black patches also appear on the stems as it progresses. In rare cases I've lost the plant altogether.  I'll add a couple of photos showing a couple of affected plants (sorry, I don't know why they get rotated when I upload them):

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Does anyone have any suggestions as to what I can use to treat them? I expect it needs to be something systemic and maybe I need to go for something fairly potent. Once we are through the coldest part of this winter I will try growing them out on the open (better air circulation) and see if that helps as well.

Thanks in advance for any advice anyone might be able to give!

Harleyb