Houseplants for pests and disease

Warm, still indoor air lets pests breed all year with no natural predators, so spotting them early stops one plant passing an infestation to the whole collection.

When

Every week or two all year round, and more often in warm rooms and whenever you bring new plants in.

How

1) Turn leaves over and check the undersides and leaf joints for aphids, mealybug (white fluff), scale (small brown limpets) and red spider mite (fine webbing and speckled leaves). 2) Look for sticky honeydew and black sooty mould. 3) Check for grey mould, yellowing and soft rot from overwatering. 4) Isolate any new or infested plant away from the others. 5) Wipe off small numbers by hand or with a damp cloth.

Notes

Red spider mite thrives in dry, warm air, so raising humidity helps hold it back. Quarantine shop-bought and gift plants for a couple of weeks before mixing them in.