Thrinax radiata

[glbower]

My double Thrinax radiata has been thriving since being planted last fall; it's about 3 feet high and growing well. Last week, a mysterious brown stain appeared on some of the leaves of one of them. The tissue appears to be OK, althought the brown color goes clear through to the other side. I'm thinking fungus, but I've never seen anything like it.

Also, the newest spear has developed holes with a brown necrotic rimg around them. Pic follows.

Any ideas?

[glbower]

The holes in the emerging spear.

[Rusty on Pine Is.]

The two photos show what appear to be two different events, to me.

    The second pic may or may not be fungal, but IMO it shows that the causal agent affected the spear before  it unfurled, in that the damage seems to be symmetrical, like unfurling paper dolls.

    It alos looks like it has done it’s thing and moved on.

    The first pic doesn’t look like the second, and really doesn’t show the classic fungal signature……there doesnt appear to be  a graduation of damage in the affected area, i.e. going from necrosis to a halo of marginal tissue.

    There are smuts that will cause brown spots, but it also appears that it could be mechanical in nature, like splash…..check to see if there are any tiny, raised black dots on the underside of the brown areas…they would be fruiting structures of a fungus or mold or smut.

    But all that is academic isn’t it…so the big question is really, ‘what da heck do you do about it?

    For now, nothing….. abt a week later, try to duplicate the pics you’ve posted, and see if the areas spread….sometime fungi are opportunistic, only affecting tissue as a secondary agent, and will stay put.

    Check other leaves too, and see if there is any activity there.

I wouldn’t take any other action till I knew if it is moving.

Hope this helps

Rusty

[glbower]

Rusty -- thanks for the thoughtful reply.

To answer your questions, yes, I'm pretty sure too that there are two separate things going on with this palm.

I think the damage on the emerging spear may be done with. It doesn't appear to be spreading.

The brown-stain area doesn't have any of the classic fungal symptoims -- no fuzz, no black spots or fruiting structures, no necrosis around the edge and the leaf tissue feels completely normal.

I know it's not mechanical damage or splash (the pattern is identical on both both sides of the leaf) and it's clearly not an insect or pest problem.

It just seems by process of elimination it has to be fungal related. As you know, we've had a really humid wet time of it the last month or so in Soutwhest Fla. I've got fungus on stuff where it's never appeared before.

It would be just my luck to get some kind of exotic fungus on one of my favorite palms. You would think the T. radiata, a native, could withstand a fungus attack, however.

I'll monitor spread and size, but I'm tempted to blast it with a fungicide.