Yellow Leaves on a Vinca

Phytophthora Stem Blight and Root Rot

• Both annual and perennial vincas are susceptible to root rot and stem blight. These fungal diseases cause the roots to blacken or yellow, and the leaves to become scorched or yellow. Plant growth is stunted and the plant eventually dies. Stem blights and root rot are more prevalent in wet, cool conditions. Avoid over watering and over fertilizing vincas, which make them more susceptible to disease. Vinca is fairly drought tolerant. It needs about 1 inch of rainfall per week to thrive. Water it deeply once or twice per week during dry conditions. Remove and destroy infected plants. Black root rot and Rhizoctonia stem and root rot cause similar symptoms. Remove diseased plant material and spray them with a fungicide.

Leaf Spot

• Wet leaves spread leaf spot, but can be treated with fungicide applications. The disease first appears as small lesions or spots on the plants' leaves. Eventually the leaves turn yellow and drop, followed by the death of the plant. Avoid watering vinca with overhead sprinklers because wet leaves spread the disease.

Tomato Spotted Wilt Virus

• Tomato spotted wilt virus spreads because of tiny thrips and usually invades the vegetable garden. The virus occasionally infects vinca, causing black spots or lines, followed by yellowing leaves and stunted growth. Remove all diseased plants so the virus doesn't spread and avoid planting vinca near a vegetable garden.

Cultural Conditions

• Annual vinca thrives in full sun, in warm, dry soil. In shade, the plant's leaves may turn yellow and the plant won't bloom well. Vinca minor grows in both sun and shade, although it is most commonly grown under trees in partial shade. It blooms better in full sun, but the leaves may become scorched or yellowed, especially in winter.