It is also important to avoid wetting the flowers when watering and crowding plants. Adequate spacing between the plants can promote good air circulation. Control can also be achieved with the use of fungicide sprays applied as soon as symptoms are visible. Among the compounds registered for use in Connecticut are chlorothalonil, benomyl, and thiophanate-methyl. Consult the label for dosage rates and safety precautions.
Petunia is susceptible to several of the viruses which are also found on tomatoes and potatoes.
Light and dark green mottled areas, mosaics, and crinkling of leaves indicate infection by the tobacco mosaic virus. Other viruses may result in dwarfed, cupped leaves and witches'-brooms symptoms. Control of these diseases is focused on prevention since once plants are infected, they cannot be cured. It is important to eliminate and remove infected plants as soon as they are recognized and to eliminate other symptomatic plants since these viruses usually have very broad host ranges. It is also helpful to place petunias at some distance from other solanaceous plants such as tomato, flowering tobacco, potatoes, eggplant, and peppers to further reduce the chances of infection.