Citrus mealybug

Scientific name

Planococcus citri

Description of adult

Adult female citrus mealybugs are white, about 3mm long, and covered in a white mealy wax. There are 18 pairs of short waxy filaments around the margin of the body. These are shorter at the head end, and lengthen progressively towards the rear end. The last pair are one quarter the length of the body. They have yellow body fluid observable if the insect is crushed.

The males are short-lived insects. They are similar to the males of armoured scales (Pseudaulacaspis pentagona), with 1 pair of fragile wings and non-functional mouthparts. They have 2 long filaments at the rear end.

Immature stages

The pale yellow eggs are laid in an elongated, loose, cottony egg sac extending beneath and behind the female. About 300–600 eggs are laid over 1–2 weeks. There are 3 moults for females, and 4 for males. The immature stages are similar in appearance to the adult female.

Life history

The eggs hatch in about a week. The complete lifecycle takes about 6 weeks during the warmer summer months. In Queensland there are at least 6 generations per year, 4–5 in New South Wales and 3–4 in Victoria and South Australia.

Distribution

Citrus mealybug occurs throughout Australia but is much more common in coastal districts and in the areas north of Sydney in the eastern states.

Host range

Hosts include casimiroa, citrus, cocoa, durian, mabolo, rambutan, rollinia, soursop and many ornamentals.

Damage

Major and frequent pest. Mealybug crawlers settle under the fruit calyx in early November. Later they move to depressions on the surface of the fruit or settle between adjoining fruit. Heavy sooty mould results, causing end rot and fruit drop.

Control

Monitor at fortnightly intervals from mid-November to near harvest. Sample 5 fruit per tree on each of 20 randomly selected trees per 1–5ha block. Apply spray if 25 or more fruit are infested with 1 or more mealybugs, and if less than 10 fruit have 1 or more Leptomastix dactylopii (main parasitoid) and/or Cryptolaemus montrouzieri (main predator) present.

Biological

The most important predator is the mealybug ladybird (Cryptolaemus montrouzieri). The larvae are white and mealy with long waxy appendages and grow to 10mm. The adults have black wing covers and other parts are reddish-brown. The ladybirds are about 4mm long. Both adults and larvae feed on the mealybug and, once established, the predator is able to control heavy infestations in 2–3 months. It is, however, sometimes slow to locate an infestation.

Lacewing larvae (Oligochrysa lutea) also help to control the pest. The introduced parasitic wasp, Leptomastix dactylopii, is very effective. This parasitoid should be liberated at 5 to 10,000 per hectare, once during October to January and is especially recommended for rollinia, soursop and casimiroa. Heavy ant infestations seriously affect natural enemies. Use a residual spray to the base of the tree to control ants. Serious infestations are often the result of insecticides suppressing natural enemies.

Chemical

Spray tree. Spray soil around the base of the tree for ants.

Chemical registrations and permits

Check the Australian Pesticides and Veterinary Medicines Authority database for chemicals registered or approved under permit to treat this pest on the target crop in your location. Always read the label and observe withholding periods.