I am informed that the A91 will be closed between Monday 10th and Friday 14th August 2015 for carriageway upgrades:

http://www.clacksweb.org.uk/transport/roadreport/

I am sure that the diversion will be clearly signed but anglers heading in either direction between Tillicoultry and Dollar will be able to use the B9140 to access either side of the roadworks.