If summer around Lago Maggiore is all about music festivals, then autumn is definitely all about the sagre, the food festivals. I've recently added several sagra dates to the Stresa Sights calendar. I'll continue to add dates as they are set. Many towns arrange a sagra, which usually extends over a weekend. Going on right now is the Sapori di Gusto, in Baveno from September 2 to 4. Arona has events scheduled every weekend throughout September. So far on the list are sagre centered around mushrooms, blueberries, grapes, apples, as well as several that will feature many regional foods.
I'm getting my information from the Distretto Turistico dei Laghi website, where Filippo is continuously adding new sagre to the list. Also on the site is a list of local hotels and B&Bs near the sagre sites that are offering special weekend packages and deals for the festival weekends. Take a look... buon appetit!