If summer around Lago Maggiore is all about music festivals, then autumn is definitely all about the sagre, the food festivals. 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, which constantly adds new sagre to the list. Also on the site is a list of local hotels and BandBs near the sagre sites that are offering special weekend packages and deals for the festival weekends. Take a look... buon appetit!

The Distretto site, by the way, is a wonderful resource for information about the lake area, extending much farther afield than we do here on Stresa Sights. It is published first in Italian but the language can be changed to English, and you might try a translator on your computer as well. You can also mail them  with questions or requests for more information here:  http://www.distrettolaghi.it/contact