Post category: Pests and Diseases


House plants are attacked by quite a few kinds of pests because these appreciate the warm conditions, soft growth and the absence of predators.

Greenflies are the most common houseplant pest, greenflies, can appear on any plant at any time of year. Black, sooty moulds may grow in the greenflies excretions.

Red spider mites cause yellowing and curling of leaves and are difficult to control. Busy lizzie is often attacked.


Red spider mite damage


When a plant infested with white fly is touched, tiny white flies fly out. Though not as common as the other two, whitefly can cause severe stunting too.

Scale insects are protected by waxy scales and these sap-suckers can reduce growth and cause leaf-fall, especially on evergreen plants such as citrus. Scale insects can be controlled by dabbing with cotton wool dipped in methylated spirits.

Caterpillars and earwigs sometimes eat holes in houseplant leaves. Affected plants are usually near an open window. Damage is usually slight and not worth controlling.

Vine weevil grubs eat the roots of many house plants, especially cyclamen and woody plants. The adult weevil crawls into the house and lays eggs in the compost. Sudden wilting, although plants have been watered, and the presence of white grubs in the compost are the usual indicators.

Tiny black mushroom flies crawling on the surface of the compost, lay eggs that can feed on the roots as tiny larvae. These are an indication of over-watered compost and can be controlled by allowing the compost to dry out for a time.

Among the specific houseplant insecticides are: Derris, Malathion, Tumblebug, Kerispray, Bio Sprayday and Picket. Take the plants outdoors for spraying and spray all affected plants at the same time to avoid re-infestation.

Repeat if necessary. Alternatively, plants can be immersed, pot and all, in a bucket of diluted spray material. Use rubber gloves.

Root-rot is the most common disease of house plants, usually caused by over-watering. Affected plants often die.

Leaf and stem-rots are caused by various fungi, but mainly grey mould or Botrytis. Avoid over-watering or misting in the dormant season. Place plants in a warmer, brighter place. If they do not recover, discard them.