Hi, I've been trying very hard to clean the black, yucky stuff off my potted lemon tree, from a white fly infestation...now I have ants!!!!! Why are they there? Ever since they've arrived the leaves are turning yellow...what's going on with my poor tree? (The yellow is recently from a pollen cloud). Thanks.

Hi Somaly, the ants are on your citrus because you still have insects on the plant that excrete a honey dew as they feed on the sap, the ants are feeding on the honey dew. It will either be caused by scale insect - tiny brownish bumps on the stems and leaves, or aphids on the new growth. The black sooty mould you describe is a fungus that lives on the honey dew. It does not harm the plant, but reduces vigour and weakens the plant, as do the sap sucking insects. This is the reason the leaves are starting to yellow, but it could also be the time of year, it is quite normal for citrus to start to yellow coming out of winter going into spring. As you can't get to the garden centre or your local DIY store at the moment, try mixing 1 tablespoon of liquid soap with 1 litre of water and spraying the plant, making sure to spray to run-off and getting the underside of the leaves. The best soap to use is pure liquid soap, dishwashing liquid will suffice, as long as it doesn't have any bleach agents in it. If you have any horticultural spraying oil in your shed, use that as well to help remove the insects, or remove them using your fingers. Feed your citrus now in early spring with a controlled release fertiliser suitable for plants in pots and containers, check the supermarket for this. Feed your tree again in late summer, early autumn. Make sure your citrus is well watered throughout the growing season, at least once a week, maybe two or three times, depending upon the weather. Lianne, Tui Team.