This is the best time of the year to control your most troublesome weeds such as Marestail, thistles, winter annuals, etc. Fall weed control helps you manage these weeds before they become a problem and is the least expensive time to combat them. You should be able to accomplish this for under $10 per acre.
When looking at specific products, I recommend a blend of Dicamba and 2,4-D because they cover a broad spectrum of weeds and can rotate to either corn or beans. Also, be sure to use an oil or surfactant as they dramatically improve the effectiveness of these products in your tank.