Home & Garden

Scale insects - getting to the root of the problem

LAST year, many gardeners had a wide range of ornamentals ruined by the handiwork of scale insects.

Scale insects are hard to recognise, being tiny in the extreme and varying in colour from light brown to grey.

They attach themselves to the underside of Camellia leaves and a host of other plants in order to feed, increase and remain unnoticed.

Found mainly on the leaf veins they boast neither arms nor legs, indeed no moving parts of any consequence.

As they feed on their host plants (camellias as outlined also agave, citrus plants, holly, ornamental ivy and others) they secrete a sugary, sticky liquid from their gut’s terminal opening, and this is kicked away by the scale only to land on leaves and shoots beneath their feeding position.

At this stage the excreted liquid is called ‘honey dew’ due to its sticky sweetness.

This waste product then becomes a bigger problem as it ages.

It develops a black coating on the plants foliage (illustrated) giving the plant an ugly, unhealthy-looking appearance.

Eventually, the entire plant is covered by what is now aptly called ‘sooty mould’.

The sooty coating is caused by saprophytic fungi.

It is not a disease and does not infect living plant tissue.

However, a heavy coverage can reduce photosynthesis thus causing a distinctive yellowing of leaves, but it does not harm the plant in any other way.

Light coverings of the mould will gradually disappear during dry sunny weather when its nutrient source is eliminated.

It can also be physically washed off all plants and this I highly recommend.

Use warm water, to which has been added a generous squirt of washing-up liquid.

When the offending discoloration has been softened and removed, spray the plant with a garden hose to clear away excess soap.

Chemical control of scale insects is effective if the root area (not the foliage) is drenched with Provado Vine Weevil Killer.