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Mealybugs in coffee

Bruno Pinese, Harry Fay & Rod Elder, Department of Primary Industries and Fisheries.

Coffee- Citrus mealybug (Planococcus citri) on a twig.
Citrus mealybug (Planococcus citri) on a twig.

Description

There are several species of mealy bugs that are similar in appearance although the differences are great enough that the species can be separated with the naked eye. Citrus mealy bug is described as an example in detail.

Adult

Adult female citrus mealy bugs are white, about 3 mm long, and covered by 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 or aphids, with one pair of fragile wings and non-functional mouth parts. They have two long filaments at the rear end.

Immature stages

The pale yellow eggs are laid in a elongated, loose, cottony egg sac extending beneath and behind the female. About 300-600 eggs are laid over 1-2 weeks. There are three moults (stages) for females, and four 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

Casimiroa, citrus, cocoa, coffee, durian, mabolo, rambutan, rollinia, soursop and many ornamentals

Management

Importance

Major and frequent pest

Damage

This insect causes damage to casimiroa, cocoa, coffee, durian, mabolo, rambutan, rollinia, soursop. 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.

Action level

Monitor at fortnightly intervals from mid-November to near harvest. Sample 5 fruit per tree on each of 20 randomly selected trees per 1 to 5 ha 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.

Control methods

Biological

The most important predator is the mealybug ladybird Cryptolaemus montrouzieri. The larvae are white and mealy with long waxy appendages and grow to 10 mm. The adults have black wing covers and other parts are reddish-brown. The ladybirds are about 4 mm long. Both adults and larvae feed on the mealybug and, once established, the predator is able to control heavy infestations in 2 to 3 months. It is, however, sometimes slow in locating an infestation. Lacewing larvae Oligochrysa lutea also help to control the pest. Parasitism by the introduced parasitic wasp, Leptomastix dactylopii is very effective. This parasitoid should be liberated at 5 to 10 000 per ha, once during October to January and is especially recommended for rollinia, soursop and casimiroa. Heavy ant infestations seriously affect natural enemies and should be controlled by a residual spray to the base of the tree. Serious infestations are often the result of suppression of natural enemies by insecticides. The ladybeetles and wasps can be obtained from ‘Bugs for Bugs’ at Mundubbera Queensland, phone (07) 41654663.

Chemical

Ants are attracted to and feed on the honey-dew produced by the scales. They disrupt natural enemies of the scale and should be controlled by spraying the soil round the trunk with chlorpyrifos or banding with tanglefoot. Some ants are predatory on ciciada nymphs and their control may lead to cicada problems.

October 7th, 2010
Topic: AGRICULTURE, FOOD DRINK, FRUIT VEG SMALL CROPS, INSECTS REPTILES, PESTS DISEASES BACTERIA VIRUSES, PLANTS CROPS WEEDS Tags: , , , , ,

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