Thrips

It’s important to recognise that pests are part of nature and even if you manage to get rid of them once, they could come back. My attitude is to keep thrips under control, rather than aiming for eradication. A few thrips are unlikely to kill your plant, but an infestation can severely damage it. The best line of defence is checking plants regularly: look for silvery, sunken patches on the leaves, often with black dots around it, which is the excrement. Adult thrips are brown/black and long and thin, and can be seen crawling slowly on the underside of leaves. To remove them, use masking tape, pressing it onto the leaves and pulling it away (this also picks up the larvae). Spray with horticultural soap, and repeat every three days. You could also release predatory mites such as Stratiolaelaps scimitus, Amblyseius andersoni or Orius laevigatus.

Powdery mildew

This is a difficult one to tackle once it has taken hold – it’s a fungal disease that appears as a white powder on the leaves. One remedy is a 50:50 solution of rubbing alcohol (surgical spirit) and water. Test a small area first to see how your plant reacts, then rub onto the leaves. You can also try adding a little horticultural soap to the solution. Again, test before spraying the whole plant. It may be that you can’t rid the plant of the mildew completely, but can keep it under control with repeated applications.

Yellow leaves

Poor drainage, damaged roots, compacted soil and nutrient deficiencies can all contribute to yellow leaves. The symptom is most commonly associated with overwatering, but it’s not the water alone that causes the problem. The other key factor to consider is how much light the plant receives and therefore how quickly it is using water. The more light it receives, the more water it can use. Moving your plant to a brighter location allows it to use the water in the soil faster, which reduces the risk of root rot.

Spider mites

These are difficult to spot with the naked eye, so look for signs of their presence, such as webbing between the leaf stems and main stem, under leaves and near the base of the plant. To treat, firstly try spraying the undersides of the leaves with water in the shower, then wipe dry with a cloth. Repeat every three days. Alternatively, spray the whole plant with horticultural soap (test an area first) and pay particular attention to the base and undersides of the leaves. The soap only kills the adults, so spraying has to be repeated every three days to kill the emerging larvae. Lastly you could try releasing predatory mites called Phytoseiulus persimilis, which feed on spider mite eggs, larvae and adults.