Wilt is caused by a bacteria that is transmitted to the plants by cucumber beetles. The only control is to prevent the beetles with insecticide before they cause the disease. It is incurable once the plants get it. It is true that one recommendation is to rotate your susceptible plants to new soil. But that is because the bacteria survives winter in the guts of the beetle larva in your soil. You could discard your old soil and start with new, but that wouldn't deal with beetles in areas outside the containers. I'm assuming you intend to keep some of your old potting mix next year. You probably should at least replace the top layer with new potting mix. But the most effective thing would be to use insecticides to protect your plants from the time you put the plants out. I like Spinosad or Neem as organic insecticides that are pretty safe. You can also choose plants that are resistant to the beetles, like Diva cucumbers.

Here is a link that might be useful: Information about wilt

"But that is because the bacteria survives winter in the guts of the beetle larva in your soil."

That is the best piece of information I've been missing in all my research. Thank you so much.

So my plan is to remove the top couple of inches of soil and remove any debris around my containers.

I didn't have cucumber beetles (that I could see, anyway); I had squash bugs. Although I haven't been very reassured by what I've read about the effects of neem on them, there's only one way to find out for myself, of course, and I'll probably be using it anyway for other pests.

My understanding is that squash bugs carry a virus in their guts in the same way, and spinosad is very effective against all chewing beetles (not lady bugs, which don't chew plants). There's a lot of discussion about it in the organic growing forum, including the long running discussion I will link to below. You do need to avoid spraying when bees are active and need to not spray the flowers, but I believe it is otherwise safe. It's in the pills I give my dog to prevent fleas.

Here is a link that might be useful: More about Spinosad

That was a powerful link, lol. Thank you. I read every word. I can use row covers for only one bed of squash. The rest are trellised, and I'm afraid I'll miss eggs since the trellises are so tall. Spraying and successive planting seems to be the best option, since, as one poster noted, it only takes one bug with a dirty mouth to kill a plant with wilt.

I do have a very happy bee colony that I try to keep happy with plants they love, and imported lady bugs (though I'll have to see if they're still around this coming year). So I'll definitely be careful.

I have never experience wilt with my cucurbits. But I have heard that one of the causes can be squash vine borer.

This post was edited by seysonn on Sun, Nov 10, 13 at 23:27