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How To Spot When Your Houseplant Is Infested With Pests

Don't let bugs get the better of your houseplants

Houses provide the perfect environment for insects to breed, as there is no harsh winter to kill them off. You have to be vigilant and take action as soon as you spot them as a couple of greenfly can quickly become an infestation. As soon as you spot bugs isolate the plant to prevent them spreading to other plants. If you don’t want to use an insecticide and the plant is fairly robust put it outside in summer and feed the birds, who will repay you by picking off the insects.

Keeping the plant strong and healthy is the best defence against insects; don’t stress the plant by over or under watering or placing it in too hot a position. Don’t over-feed with a high nitrogen fertiliser as this just produces a lot of soft, sappy growth which attracts aphids.

When buying a new plant avoid any which have a lot of soft, sappy growth or any which are bone dry. Also avoid any which are pot bound or have brown patches on the leaves.

Calathea

Calathea

Aphids

These small green or reddish insects are sap suckers which love soft new growth and flower buds. They secrete honeydew which in turn is an ideal breeding ground for sooty fungus. Rub them off between the thumb and index finger then spray with either a soap and water solution or a systemic insecticide.

Mealybug

These small, white, fluffy insects hide underneath the leaves, in leaf axils and along stems. The best way to eradicate them is to swab them with a cotton bud soaked in rubbing alcohol; you will have to do this every few days until they have all disappeared. Make sure you just swab the insects and not the whole leaf. Spray with a systemic insecticide just in case you have missed a couple. If the infestation is particularly bad the best course of action would be to dispose of the plant. They particularly love cacti and succulents where they can be quite difficult to spot; they also love African violets, croton, begonias and coleus.

Kalanchoe - double

Kalanchoe - double

Scale insect

These small, flat, disc-like insects stick to the underside of leaves and along the stem; they are particularly difficult to spot. Again they are a sap sucking insect which secretes honeydew. Swab them off with a cotton bud soaked in rubbing alcohol, taking care not to cover the whole leaf. Spray with a systemic insecticide in case you have missed a couple.

Spider mite

Often the first sign of an infestation of spider mites is a yellow mottling of the leaves; if left untreated they will eventually kill the plant. They thrive in a hot dry atmosphere so misting plants will help reduce the chances of an infestation. They are extremely difficult to see so you may need a magnifying glass. If you have a fine mist sprayer spray the plant and their webs should show up. They are difficult to treat as the infestation is often quite heavy before you spot them, if this is the case you may well have to destroy the plant. Spray every 2 - 3 days with a systemic insecticide. If possible submerge the foliage in a bucket of tepid soapy water (3 teasp washing-up liquid to a gallon); wrap the pot and compost in a plastic bag to prevent the compost falling out. This method is not suitable for plants with soft, hairy leaves, such as African violets or gloxinias.

Schefflera (Umbrella Plant)

Schefflera (Umbrella Plant)

Thrips

These are tiny black flies which live on the surface of the compost and tend to fly close to the surface; they are most visible if the plant is disturbed. They cause silvery streaks on the leaves and spots on the flowers. A hot and dry environment is ideal and they will multiply rapidly so action must be taken at the first sign. Spray with an insecticide, not forgetting to also spray the surface of the compost.

Whitefly

These are tiny white moths which lurk on the underside of the leaves. If the plant is disturbed you will be able to spot them flying. They are a sap sucking insect who secrete honeydew which in turn provides an ideal breeding ground for sooty fungus. If there are a lot of larvae clustered in one spot the best course of action would be to prune out the infected tissue. Spray with a systemic insecticide or a solution of soapy water.

If you would like more information on keeping your houseplants healthy and happy read the blog articles or watch the videos on our youtube channel.

Angela Slater
Daughter of a farmer and market gardener so have always had a connection with the outdoors, whether it was keeping animals or producing fruit, vegetables and cut flowers. Along with my work at Hayes Garden World I also have a smallholding, mainly breeding rare breed pigs. I gained an HND and BSc in Conservation and Environmental Land Management, as a result I am an ardent environmentalist and have a keen interest in environmentally friendly gardening. In my time at Hayes I worked for several years in the Outdoor Plant and Houseplant areas