Late blight, Phytophthora infestans Worldwide, late blight is the most damaging potato disease, but because of the generally and climate of Western Australia, it is rarely seen here and does not appear to establish. The first symptoms are irregular green spots on leaves, becoming purplish-black with a yellowish halo. Tubers are also affected, initially with brownish dry rot, which frequently softens through secondary fungi and bacteria, leading to a complete collapse. Pink rot, Phytophthora erythroseptica Pink rot is a tuber disease that is restricted to the southern swamps, although most of the heavily infected, poorly drained areas have been withdrawn from cultivation. Affected plants wilt late in the season and all parts may be infected.
Affected tubers have black surface areas.
A firm rot develops, from which water may be expressed. There is no effective cbemical control for this disease, but in swamps, improved drainage removes the predisposing conditions. Control of irrigation and drainage normally prevents infection in other areas. Leak, Pythium spp. Like pink rot, leak is only seen in conditions of poor drainage.