Hi, my orange tree has a lot of black spots at the back of its leaves. I also feel the fruit are less this year. How do I treat and how to spray till the top as it’s too tall for me to reach? Thanks.

Hi Swati, thank you for the photos, the black on the topside of the leaves is sooty mould, it is caused by sucking insects such as scale or aphids and is a fungus that lives on the honey dew excreted by these insects. If you look closely you will see brown bumps on the stem, leaves and new foliage which is scale insect, or small green insects on the new growth which is aphids. The speckles on the underside of the leaf are likely caused by either thrips or spider mite. The tree looks very well established and would benefit from pruning to generate new growth, remove dead branches and if the tree is too high, reduce the height so it is more manageable for you. By doing this, you will get new growth and so more flowering and fruiting, citrus flower on new seasons growth. Make sure any pruning wounds bigger than your little finger are sealed with a pruning paste or water based paint, the time to prune citrus is when fruiting has finished. If you have a horticultural spraying oil apply that to the tree every 7-10 days, or when convenient or able, talk to your local garden centre or DIY store for a suitable spray for your tree. Spraying the tree with (full fat) milk will remove the sooty mould, but you need to control the insects to stop it coming back as the insects are reducing the vigour and health of your tree. Regular feeding is important, use a specially blended citrus and fruit tree fertiliser such as Tui Citrus food in spring and again in late summer, early autumn. Mulch around your tree using a suitable garden mulch such as Tui Mulch & Feed, this will help conserve soil moisture. If grass is growing up around the base of your tree, remove the grass as it is competing for nutrients and moisture with the tree (50cm diameter around the tree), apply mulch to keep the grass at bay. Citrus fruiting can be cyclical, one season a bumper crop, the next not many fruit, it is just nature, your tree will benefit from regular feeding and watering so it generates new growth, more flowers and ultimately fruit. Lianne, Tui Team.