Lesions expand rapidly and are black and may encompass the entire leaflet and cause abscission when conditions are favorable. There is rarely any halo surrounding lesions on China Doll. Control - Keep plants as free of excess water as possible and avoid crowding to promote rapid drying of foliage. Mixed results in controlling this disease have been seen with the fungicides available. Symptoms - Infection of small plantlets occurs all over the plantlet and results in crown or petiole rot.
Lesions also appear at edges, tips and at broken leaf veins on zebra plants.
Examination of the lower leaf surface generally reveals sporodochia which are irregularly shaped, black and have a white fringe of mycelia. Control - Avoid temperatures between 60 and 85 F when possible, minimize wounding, and fertilize plants at recommended levels. Root and stem tissues become water-soaked necrotic and collapse. On larger plants wilting, yellowing and stunting can be signs of Phytophthora crown and root rot. Overwatering will make Phytophthora crown and root rot more severe and use of appropriate fertilizer levels is critical.