The Zimbabwean Gardener Issue 1 Winter 2012 | Page 27

AskHenning Q&A Let Henning give you the answer to the problems in your garden Q A The most common question I am asked in the nursery is about a black residue on plants. It seems to start with palm trees, cycads and then moves onto the other plants in the garden. If your plants are covered by an unsightly, black, sooty growth, the problem you are facing is called sooty mould. Sooty mould is a fungus, which covers plant leaves, stems and twigs with a black sticky substance. In most cases, the sooty mould is often found on plants infested with sap sucking insects, which produce a sugary secretion called honeydew. These insects include aphids, scale, mealy bug, ants and whitefly. This honeydew has a lot of sugar in it and provides an ideal host place for sooty mould to grow. If you get rid of the insects, it will remove the source of the honeydew and dry up the sooty mould, which will eventually wash off the foliage. I recommend cutting off all the infected leaves, as they will never recover to optimum health. Be ruthless and destroy the enemy! I would recommend the following chemicals to get rid of the aphids. They are available at most nurseries. Rogor, Dimethoate, Confidor, Pilarking35Sc, Imidaclorprid, Aktara If you get rid of the insects, it will remove the source of the honeydew and dry up the sooty mould, which will eventually wash off the foliage. The mould itself doesn’t feed on the plant, but because it covers the leaf surface, it blocks the light and reduces photosynthesis, which is essential to plant growth. However, the good news is that if you have the patience and time, black sooty mould covering any part of the leaf, stem or branch can be rubbed off with soap and water. The problem is that most of the infected plants are too big and large. As I mentioned before, cut it off and let nature supply you with healthy new stems and leaves. TOP RIGHT: RIGHT: Sooty mould on palm frond Mealy bug About Henning My wife and I have been involved in the garden industry and landscaping for many years. Recently, we said farewell to Village Walk and we are now operating from Henning’s nursery at Honeydew, Greendale. If you have any questions about your garden, email your questions to [email protected] and I will answer them in the next issue. Email your questions, photos and plant problems to Henning [email protected] 27