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Red-shouldered leaf beetle

  • Redshouldered leaf beetle (Monolepta australis). Courtesy Dr Alan Bishop
    Red-shouldered leaf beetle (Monolepta australis). Courtesy Dr Alan Bishop.
Scientific name

Monolepta australis

Description of adult

Beetles are about 6 mm long, yellow in colour with red patches over the shoulders and near the distal end of elytra (wing covers).

Immature stages

Small (less than 1 mm) yellowish oval flaccid eggs are laid just below the soil surface near the base of the plant. Larvae are white, slightly dorso-ventrally flattened with sclerotised (hard) brown plates head and tail.

Life history

Eggs are laid in the soil surface, mainly in pastures, and the larvae, which are about 5 mm long when full-grown, feed on the grass roots and pupate in the soil. The life cycle takes about two months during summer and there are three to four generations annually. Adults usually emerge from the soil after good rains following a dry spell. If larval populations in the soil are high, the multitude of emerging beetles will form an aggregation and swarms may migrate into tree crops at any time of the year.

Distribution

This pest occurs in fruit-growing areas throughout Queensland, northern NSW and the Northern Territory. Other chrysomelid beetles, black swarming leaf beetles, cause similar damage in south Queensland.

Host range

The host range is large and includes avocado, carambola, cotton, corn, Eucalyptus spp., grasses, legumes, longan, lychee, macadamia, mango, strawberry and numerous ornamentals.

Damage

Minor and sporadic throughout Queensland and northern New South Wales.

Larvae feed on plant roots. Adults skeletonise foliage, especially on flushes. Swarms can invade the orchard and cause serious damage within 2-3 hours.

Control options

Examine whole orchard at regular intervals. Check flowers and new growth for beetles particularly following the first substantial rain after a dry spell. If beetles are swarming in well-established orchards, only 1-2 trees may be affected. Large swarms in young orchards will spread over more trees and cause proportionally more damage. Control is limited to spraying when beetles are active and damage is evident. Give consideration to the effect on bees if application is required at flowering time. Disregard individual beetles or groups fewer than ten if they aggregate on split fruit. Only swarming beetles in a feeding frenzy cause damage.

Cultural

Eucalyptus torelliana as a windbreak is highly attractive to these beetles and is useful for early detection and control. Yellow sticky traps in boundary trees provide an early indication of beetle presence.

Chemical

Spray affected trees.

Chemical registrations and permits

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

Last updated 06 January 2012