Pest Problems Explained – MEALYBUGS

Mealybug Description

Mealybugs are small, soft-bodied insects which have sucking mouthparts. The females are oval in shape and can be up to 5mm long. They are white or whitish-pink in colour and are generally covered in a white waxy material. They have filaments made of wax around the edge of their bodies and tails.

The most common species found in glasshouses are the citrus mealybug which has very short tail filaments and a central grey stripe, the vine or glasshouse mealybug which has a pair of tail filaments about half the body length and no stripe (see right) and the long-tailed mealybug which has waxy tail filaments as long as the body and a grey stripe.

Mealybugs (Planococcus Citrus) on an orchid leaf.

The males, if produced by the species, are small and elongate in the young stage and develop into delicate winged insects.

Mealybug Damage

Mealybugs are often found in clusters on stems and leaf whorls. They produce honeydew which often leads to sooty mould growth.

Large colonies can weaken the plant because of the amount of sap being taken which can result in yellowing leaves & defoliation.

Mealybugs feeding from the stem of a plant

Root-feeding species are seen as white patches among the roots when re-potting, especially around the sides of the root ball.  Care is needed to distinguish them from root aphids

Mealybug Life Cycle:

Most mealybug species lay eggs. However, the long-tailed mealybug gives birth to live young, whilst the citrus & vine mealybug produce quantities of “waxy wool” in which they can lay up to 500 eggs.

Egg laying may take up to 10 days and reduces the size of the female mealybug considerably. The female dies once she has completed laying her eggs.

Once hatched the young, or “crawlers” as they are sometimes called, are very mobile. They disperse rapidly and find suitable sites in which to feed and settle. The females continue to feed until they are mature enough to lay eggs.

The complete life cycle takes approximately 50 days at 20ºC (68ºF), this is reduced to 25 days at 30ºC, higher temperatures may inhibit egg laying.

Biological Control of Mealybugs.

Mealybugs can be controlled biologically in greenhouses or conservatories by using their natural enemies Cryptolaemus or Parasitoids or a combination of both.