Is this Black sigatoka?
 

I bought a Cavendish at Home Depot a couple of months back. It has grown very quickly and looks great. However, the bottom leaf started looking bad (yellow veins; brown on the end) a few days ago and now the next few leaves are peppered with tiny black spots.
Is this black sigatoka? If so, should I dig it up and toss it? I have two ice creams, an African Red, and another that I can't remember the name of (blush), and I don't want to lose them. From what I read on Wikipedia, black sigatoka will kill my Cavendish and can't be treated. I'd rather lose the one (albeit lovely) Cavendish than the rest of my babies.
Thank you in advance to anyone who can weigh in. For some reason, I've only been able to upload one picture (below).
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Re: Is this Black sigatoka?
 

hummm ... try scraping the spots. See if they are 'ON' the surface or 'IN' the leaf. ... My first thought seeing the photo that those might be insects. Cant tell from the photo.

Re: Is this Black sigatoka?
 

You can treat and live with Black Sigatoka. Those black spots are probably not black sigatoka, though. Here in Florida it is mostly a wet season problem.

Re: Is this Black sigatoka?
 

The spots are spreading and the lower leaves are dying--turning yellow and brown and curling. New cigar leaves all have some black areas near the tips. I wish I could upload more pictures! Can anyone tell me how best to treat this? I've read that there is a new organic treatment --Timorex Gold--but it's not commercially available in the U.S. yet.

Re: Is this Black sigatoka?
 

Like Nicolas said, you do not have Black Sigatoka, and even if you did, it does not really kill plants, it can severely reduce yields in some cases, but is as far as serious banana diseases go it is relatively easy to deal with.

Anyway, I can't say exactly what these spots are, there are a number of minor leaf diseases which can affect your bananas, sometimes harmless insects can also cause spots like that, but unless the plant really stops growing or a majority of the leaves or surface area of the leaves die, then I wouldn't worry about it. You mention that the lower leaves are dying, but that is normal as the plant grows even in perfectly healthy plants, and if there is any stress such as lack of water, nutrients or if it is pot bound, the lower leaves are normally the first to be shed from the plant.

Re: Is this Black sigatoka?
 

If you think this is a fungus, then spray with copper sulfate. It can be bought off the shelf or you can mix your own. I use a lot, so I mix my own and filter through a paint cone filter so it will not clog up it sprayer.

However, this does not look like a fungus to me, but may be an insect. Either those tiny spots are the insect or the bit mark left after the insect feed. Look in the top of the pstem for the hidden infestation.