Streptocarpus is a plant that has become popular for ornamental use in the home. Originally imported from the African continent, growers now produce them commercially so you are likely to find some specimens that were grown near your locale. Streptocarpus are generally hardy, problem-free plants, but three diseases are of paramount concern for the grower.
Appearance of a Healthy Streptocarpus Plant
A healthy streptocarpus will have large, narrow green leaves with a non-glossy surface and a moderate amount of veining. The edges will be curved and wavy, but unmarred and without a pointed tip. Blooms should be moderate in size and come in a wide range of vivid colours.
Fungal Diseases of Streptocarpus Plants
Crown rot is a serious infection that is easily identified by the wilting leaves, weak stem, and rope-like white growth of the fungus on the roots of the plant. It can occur when the soil is already infected, is overly moist, or the cuttings have been buried too deeply when transplanting. Botrytis is a mould that affects the stems and leaves of the plant, particularly during the rainy season when humid, moist weather provides the ideal conditions for infection. The streptocarpus plant will develop brown or black spotting and may shed a silver dust, which is indicative of spore formation.
Foliar Nematode Infection of Streptocarpus Plants
A distinctive warning sign of nematode infection in your streptocarpus plant is when the leaves of the plant shrivel up towards their centres. In its early stages it can be somewhat difficult to detect, as the brown spots first develop on the underside of the leaf surface. It is of paramount importance to keep nematode infection from spreading, which is done by minimising the amount of standing or splashed water in the vicinity of the plant. Nematodes live and travel in soil and water, so using sterile soil and water will in most cases prevent infection. When acquiring a new Streptocarpus plant, you should keep it quarantined for an average of a month to make sure it is not infected.
Treatment of Fungal Infected Streptocarpus Plants
The best treatment, as always, remains prevention. Avoid burying new cuttings of streptocarpus too deeply beyond the place where roots join the stem. Keep soil well drained and do not overwater. If you are unsuccessful in preventing fungal infection, the judicious application of fungicide will often be an effective treatment.