Never had an issues like this before. My vege garden's been fine for ages - and getting bigger! - but I've recently noticed some blacvk marks on my potatoes while weeding. At first I just thought it was stubborn dirt, but after poking about a bit and doing some google image searches i came across this page which looks just like it: http://www.leicesters.co.nz/rhizoctonia-solani/.
The black marks are fairly stubborn, and definitely arent dirt. It's a little too early to tell if any of the other signs have shown up, but I'd rather be safer than sorry. Is this a possibility?
Everything else seems fairly healthy, at least for now. I have had a lot of rain here recently, which my garden isn't really set up to deal with too well at the moment. Could this be the reason? Interested in any thoughts or personal experiences from anyone else who has dealt with this stuff before. Would love to work out what's happening with my potatoes. They're my favourite thing i grow at the moment *homer simpson thinking about food*
hau Mark, If you have found those black spots, you do have rhizoctonia-solani present in your soil. There really isn't anything else that looks like it. This disease can take up to three years to fully show its effects.
The best thing to do would be to change fields for your potatoes and make sure none of your seed potatoes have any rhizoctonia-solani on them prior to planting.
As you have found out, this is a persistent disease fungi that will only get worse without doing something. There are bacteria and nematodes that will attack the RS and help remove it but they will need some time to do the work.
Inoculating your current field with some fungi eating nematodes will reduce the fungi count and if you then come back with some other, beneficial fungi, they will out compete the remaining rhizoctonia-solani.
I'd work the current, infected field, with antagonists bacteria and nematodes for at least two years so it can be mostly eradicated prior to coming back to it with any potatoes.
This fungal disease is fairly prevalent in all countries that grow potato crops and it can end up decimating crops and making it nearly impossible to grow potatoes.
Thanks for the detailed response Bryant! I'm currently in the process of working the existing field while working out where I'm going to be planting (new) crops in the meantime. I'm glad I caught this relatively early, at least. And that it's only affecting one - relatively small - area at the moment. Will see how I get on. Thanks for the help!