Whitefly (Teuloroides vaporiorum) is present nearly all year round, but most prevalent in January. This tiny 1mm white moth-like insect infests the underside of the younger leaves. A heavy infestation will cause them to take off in a ‘cloud’ when disturbed. Unlike aphids, the damage they do is not that obvious, but they do excrete a sticky, sugary ‘honeydew’ that attracts an unsightly black sooty mould on the leaves.
Whitefly are prolific and go through several stages, which is important to know, in that many insecticides deal with one stage only and repeated spraying is necessary to catch all stages. The eggs and nymph stages are seen as ugly ‘scale’ on the underside of the leaves.
As with so many of these pests, you need to inspect your plants regularly and act quickly to eliminate them.
Contact insecticides are used for whitefly and several sprayings at 4-5 day intervals are necessary to eradicate successive generations. Special attention should be given to the undersides of the leaves. Ideally the same insecticide should not be used repeatedly so as to avoid resistance developing.
Insecticides – Whitefly, Garden Ripcord and Malathion can be used. Read all instructions on dosage carefully and the need to repeat spraying.
The insecticide Kohinor is an easy-to-apply insecticide and may be used once or twice during the season for aphids as well as whitefly. It can also be used as a preventative measure.
If the infestation is severe though and covers most of the new shoots, it is necessary to use an insecticide spray, but unfortunately this kills other insects that are not necessarily harmful. Confidor is a low-toxic systemic spray that enters the sap stream of the plant and kills any insect that draws sap from it.
A commercially available natural predator wasp, Encarsia Formosa, can be used to eradicate whitefly in greenhouses – this is known as Biologic Control, but it is impractical for most people.
Whitefly are attracted to yellow – a yellow plastic strip coated with sticky oil can be used as a monitor, but will not get rid of whitefly.
Environmentlly-Friendly Spray for Whitefly & Aphids
Multi-purpose Non-toxic spray:
1 Tbls Scrubbs Ammonia
1 tsp Sunlight liquid soap
10 tsp Kelpak
2 tsp Epsom salt
1 tsp Jeyes Fluid
5 litres water
Mix all the above thoroughly and only make up what you need – don’t store. Spray both top and underside of leaves regularly once a week as a precaution.