In Western Australia, cavity spot disease of carrots is caused by the soil borne fungus Pythium sulcatum. Cavity spots are small elliptical lesions – usually less than 10 mm across – often surrounded by a yellow halo. Infections can take place anywhere along the carrot root and lesions start as pinhead-size spots. In most cases, visible symptoms develop in the month before harvest maturity and develop rapidly if conditions are favourable. This fact sheet provides an overview of cavity spot disease of carrots, including effective control methods.