Common Problems Physiological Cool temperatures, high fertilization, and overwatering are the most common problems both in the greenhouse and in the landscape. Trickle or drip irrigation rather than overhead irrigation is best for watering Vinca in the landscape. In the retail area, Vinca should be marketed in an enclosed area in early spring to prevent cold stress. Insects Vinca has very few insect problems except occasional thrips or aphids. Diseases Thielaviopsis, Pythium, and Rhizoctonia are most prevalent in Vinca when the plant is under stress, usually resulting from cool temperatures and overwatering.
Pythium causes black lesions on the roots, and the medium has a musty smell.
The best prevention for Black root rot is to maintain the proper growing conditions, especially proper temperature and medium pH, and pay careful attention to sanitation. The major garden disease of Vinca is aerial Phytophora. This disease is prevalent where overhead watering splashes soil and fungus spores onto lower foliage and stems. Lesions develop on leaves and stems, killing the shoot but leaving a healthy root system. The best preventative is to use drip irrigation.