The Department of Agriculture, Fisheries and Forestry is asking home gardeners to help control late blight. The disease is transmitted by airborne spores, and if it is present in home gardens, it can spread to commercial crops with devastating results. With conditions of high humidity and temperatures, there have been a number of reported outbreaks of late blight across the province. Potato producers are taking every precaution to prevent further spread of the disease, and all possible sources must be eliminated.
Late blight is a fungal disease of potatoes and tomatoes, and attacks the foliage and fruit causing rapid destruction through rotting. An early symptom of late blight in potatoes is brown, dead areas at the tips of infected leaves. Generally, the lower leaves are infected first, but in muggy weather the entire plant can become black and wilted. Another symptom to look for is a white downy mould on the underside of leaves. On tomatoes, greenish-black and water-soaked patches develop in the older leaves. These enlarge in moist weather and may exhibit a downy white growth on the underside of the leaf. Dark coloured spots with a firm, rough surface will appear on the fruit.
Prevention is the best method of protection. Protective fungicides registered for use in gardens and available at garden centres are an effective and safe way to prevent late blight. They must be used on a regular basis as new leaves develop or as applications are washed off by rain.
Once established, late blight is very difficult to control. Infected plants should be completely removed and destroyed by placing in a plastic bag and allowed to break down under sunlight. Removal of the plant reduces the potential for further infections in the garden and in nearby commercial crops.
A copy of the fact sheet, "Late Blight Control for Tomatoes and Potatoes in the Home Garden" is available from District Agricultural Offices.