English ivy is also known by its scientific name of Hedera helix L. and is a member of the Araliaceae family. This perennial vine is often placed outdoors and is known for its climbing ability. English ivy is susceptible to sooty mould, which is a black fungus that resembles chimney soot.
Sooty mould is a velvety black fungal coating that occurs on a wide range of plants. This disease is caused by black-coloured fungi that grows on the surface of the plant. Sooty mould will not kill plants, but can cause adverse effects if heavy coverings of mould are present.
The most common cause of sooty mould in plants is insect infestation. English ivy is susceptible to infestation of mealy bugs, which excrete a sticky substance known as honeydew. This substance sticks to ivy leaves, causing sooty mould to develop. The presence of sooty mould is a symptom of heavy insect infestations.
English ivy that develop sooty mould often have a black fungal coating on its leaves and stems. Rubbing sooty mould from English ivy leaves will remove it, but the mould will soon return unless the insects are eliminated. Sooty mould is considered to be a cosmetic problem in plants, unless very heavy coverings of mould are present. In severe cases, the mould can cause plants to suffer adverse effects from reduced sunlight. Sooty mould may also cause English ivy to suffer from other insect infestations or environmental stress.
Sooty mould is best controlled by eliminating the insects causing it. Spraying your English ivy with a forceful stream of water twice each week, knocks mealy bugs from leaves and reduces sooty mould. Natural predatory insects such as lace wigs and mealy bug destroyers control mealy bugs by feeding on them. Horticultural oils work by smothering mealy bugs and is often an effective form of insect control. A wide variety of insecticidal sprays are available at your local garden centre for mealy bug control and are effective and safe if the label directions are followed.