Hi, I have a black covering on the leaves of one of my feijoa trees, it looks like mould. I am not sure what to do about it, I presume I should spray but what with?? Thanks.

Hi Warren, the black covering on the leaves is likely to be sooty mould, a fungus that feeds on the honey dew excreted by sucking insects such as scale insect, aphids and mealy bug. If you look closely you probably have ants climbing over the plant, they are also feeding on the honey dew. Eliminate the insect pests and the sooty mould will go away. Ask your local garden centre for a suitable control, but you can spray the tree with a horticultural spraying oil mixed with water every 7 days making sure the underside and top of the leaf is covered, it is safe to use at this time of year when plants are flowering. Alternatively spray the tree with a insecticide such as pyrethrum which is suitable for controlling insect pests on a wide range of plants, don’t spray while bees are foraging, wait until the tree has finished flowering before spraying with pyrethrum. Sooty mould is not harmful and is easy to eliminate, it will reduce the vigour of the tree for a while but it will bounce back. Lianne