woodlice/rotten trunk problem

woodlice/rotten trunk problem

I need some advice if anyone has any experience/knowledge in this matter. A few weeks ago I acquired a plant from a friend. It looks like a palm and you can see it here: http://www.utilitygirl.co.uk/gallery/Gardening-Part-2/IM000568 When I planted it in its container (as soon as I got it home) I noticed that the 'trunk' was slightly damaged, like it had a small chunk missing out of it. I looked it it again today (about 3 weeks later) and there is more missing from there and the area is infested with woodlice so it's likely to be rotten. Thinking back to when we dug it out of my friend's garden, I'm pretty sure that that part of the trunk was below the soil surface, so that could explain the rotting. But now that I have an idea of why it happened, does anyone know of a way I might prevent further damage and save the plant? Or is it doomed? All of the lower leaves had to be removed today because they had gone brown. It's quite a rapid deterioration in the last few days :/ Any advice/ideas would be most gratefully received.
Garden pictures this past week

Garden pictures this past week

Seven kinds of tomatoes in a small garden

Seven kinds of tomatoes in a small garden

Hi!

Hi!

My new and improved bedroom!

My new and improved bedroom!

New blooms

New blooms

Spring flowers.. a little early! x posted

Spring flowers.. a little early! x posted