It appears to be a fungus. Unless you take a specimen and send it to your land grant university for a diagnosis, you'll never know for sure what it is. I would do that. My best guess is Southern Blight. It could also be a root/petiole rot. I would also post to the hosta diseases facebook page. Maybe someone who is more knowledgeable than me will come along.

Meanwhile, I would mix up a 10% solution of hydrogen peroxide and spray the pettioles. and keep looking for a solution. The hydrogen peroxide will only slightly delay the problem, it won't solve it. If you can, move your hosta apart for more air movement, so that other hosta are not infected.

This may help you.

https://store.extension.iastate.edu/Product/sul14-pdf

bk

Looks like Southern Blight. Look for little spheres at ground level. You're supposed to be able to treat it with Bayer 3 in 1, but I don't recommend it. When I used it, the hosta recovered and looked fine. The next year it had deformed leaves, and it didn't come back this year. Generally the best thing to do is dig the plant up, wrap it in plastic, and trash it. Clean your tools and disinfect them when you're done. Search Southern Blight. Someone just posted a complete story on it.

On the chance it isn't SB, you could try a 10% bleach solution. Just dump a quart or two on the plant. Probably won't help, but it's cheap and you never know.

Throwing it in the trash is not a bad idea. However, it won't solve the problem. See all those little black dots and the webbing? My guess it's the spores of the fungus. Even if you remove the plant, unless you remove all those spores it's going to come back somewhere else.

If it's southern blight, there should be some orange "seeds" on the plant and around the ground close to the plant. If it's another fungus, the solution is the same. You've either got to kill the fungus and replant the plant (bleach solution is common, 10% bleach, I think) or trash the plant.

THEN, YOU HAVE TO REMOVE THE SPORES. Use an outdoor vacuum to remove the top layer of dirt anywhere you find the disease. The hosta library has good article on southern blight. http://www.hostalibrary.org/articles/SBarticle.htm

Be careful not to track the spores around on the bottom of your shoes and clean your tools.

Most definitely Southern Blight. Be careful it’s easy to spread. How much of the plant is left?

Here’s what happened to Punky in my garden from Southern Blight