Mealy bugs Pseudococcus spp.

Look for

Wilted, stunted and dehydrated plants which may also be losing leaves. Foliage becomes covered in a sticky honeydew residue which in turn can lead to the development of dark sooty mould. You may be able to spot colonies of mealybugs on the undersides of leaves and in the leaf joints of plants. They're usually pinkish in colour and protect themselves with a layer of white waxy coating. Mealy bugs can also attack the roots of plants, but are much more difficult to identify.

Plants affected

• Mealy bugs usually infest greenhouse and houseplants, although the phormium mealy bug, imported on New Zealand flax, will survive on outdoor plants in southern Britain.

About Mealy bugs

• Mealy bugs are small, sap-sucking insects that produce large quantities of wax.
• Most UK mealy bug species are thought to have originated in the tropics.
• Males are winged and relatively few in number. Females are wingless and have flattened, soft, oval-shaped bodies up to 4mm in length. They're pink in colour, but appear white because of the waxy powder that covers their bodies and the long wax filaments that they also secrete.
• Development from egg to adult takes about three weeks.
• Breeding can continue throughout the year on plants in heated greenhouses and indoors.
• Colonies develop on leaves, stems, flowers and fruits of plants, and consist of egg masses, juveniles and adults clustered together and protected within a mass of wax filaments produced by adult mealy bugs.

Treatment

Chemical

Products containing the following chemical ingredients are all effective on Mealy bugs

• Natural Fatty Acids
• Surfactant based products

Note: It is important to read manufacturer's instructions for use and the associated safety data information before applying chemical treatments.

Organic

• Check susceptible plants every few weeks and deal with the first signs of infestation immediately.
• Remove as many mealy bugs as you can by hand or, if possible, cut off infested shoots and stems.
• Use natural enemies such as the parasitic wasp Leptomastix dactylopii and predatory beetle Cryptolaemus montrouzieri, which are both commercially available for mealy bug control.

Prevention

• Inspect new plants thoroughly and, if possible, quarantine them for a month or so before introducing them to the greenhouse.
• Destroy all infested material since mealy bugs are fairly mobile.
• Remove dead leaves and prunings from the glasshouse because these may harbour adults or eggs.
• Wash vines and citrus trees with a recommended plant wash or surfactant-based product during the early winter when they're dormant.