It appears that the Mushroom festival for Pontremoli is held in a small town within the local goverment boundaries called: Succisa and it is held in September. However, the smaller the festival the less likely you are to find info online, they just aren't that organized. But once you are in Pontremoli you will see posters that go up with more detailed info.
The chestnut festival is called the Castagnata, and last year it was held every Sunday in October in Pontremoli.
As Donna has said, these town events are organized locally by the small towns and they never think to put any info online, mostly because they think only of locals being interested in them; if they ever do it at all, it is last minute like a week before. The most common method used here for promoting local events are POSTERS around town. That's a very handy thing to know -- once you're here, keep a lookout for posters and you'll see food festivals or other events for the time you are here, most often held on weekends. That way instead of eating at restaurant one evening, you might choose to go to a local sagra or other festival where you can enjoy local specialties with other locals.
Hi! I'm also interested in the festivals and antique markets around Tuscany. I plan to be there in October this year, and noticed you mentioned MERCATINO ANTIQUARIATO in Barga and Monticello Amiata's annual Festa della Castagna. Is there any way you could confirm the dates of these events for me? For the market in Barga, you say 2nd weekend of the month, but is this for sure every month in the year? And are you able to confirm the dates for the chestnut festival in Monticello Amiata? I cannot read the website. Thanks so much in advance!
Im also interested in going to a town festival in Oct. I'm interested in Monticello Amiata's annual Festa della Castagna. The website is all in Italian. Can you please let me know if any specific dates are mentioned for this year? http://monticelloamiata.it/la-festa-della-castagna/
Also I'm interested in MERCATINO ANTIQUARIATO in Barga. I read on an article that this occurs the 2nd weekend of every month. Do you know if this is accurate?