I just wanted to let everyone know what's up with the herbicide application signs in the recently mowed prairie area.
I sprayed this myself, and I made an effort to leave a buffer zone unsprayed 18"-24" on either side of the trails. According to the manufacturer, its safe to re-enter the sprayed area after 24 hours (IE, safe to go off-trail in this area). I'm a bit more paranoid myself, so I'd say try to keep your bike on the trail here (you know, like you always do) until the blue dye has faded away.
The prairie was mowed a month or two back by Dane Co. Parks staff, at the request of the volunteers who manage the prairie, in an effort to control brush invading the prairie. An unfortunate side-effect was that this encouraged some exotic, cool-season grasses, namely Kentucky bluegrass and reed canary grass, that are usually shaded out by the taller prairie wildflowers and grasses. So I took it upon myself to spray the area with a grass-specific herbicide to prevent these noxious weeds from getting a toe hold. This is actually a pretty good prairie planting, so I thought it would be a shame for it to loose ground to the exotic weeds.