Parts of the course have been damaged by chafer grubs which means only races run over five and five and a half furlongs can be staged.
Six races will now be contested on Sunday.
Jon Pullin, racing director at Arena Racing Company, said: "On walking the course this morning, the grounds team at Bath Racecourse discovered chafer grubs on the home bend, making that section of the racecourse unsuitable for racing.
"Bath has always been susceptible to these types of grubs, which damage the turf by eating the roots of the grass and destabilising the racing surface.
"A product called Merit Turf has previously been used to prevent the spread of chafer grubs, but this has not been possible since October 2016 when the product became illegal in the UK.
"In the last year the grounds team at Bath have undertaken a number of actions, as recommended by agronomists, to try to prevent the return of chafer grubs without chemical intervention.
"Further assessment will take place following this weekend's fixture and an update will be provided in due course."