Red-shouldered leaf beetle
Description of adult
Beetles are about 6mm long, yellow in colour with red patches over the shoulders and near the distal end of elytra (wing covers).
Small (less than 1mm) 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.
Eggs are laid in the soil surface, mainly in pastures, and the larvae, which are about 5mm long when full-grown, feed on the grass roots and pupate in the soil. The life cycle takes about 2 months during summer and there are 3 to 4 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.
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.
The host range is large and includes avocado, carambola, cotton, corn, Eucalyptus spp., grasses, legumes, longan, lychee, macadamia, mango, strawberry and numerous ornamentals.
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.
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 10 if they aggregate on split fruit. Only swarming beetles in a feeding frenzy cause damage.
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.
Spray affected trees.
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.
- Last reviewed: 19 Oct 2022
- Last updated: 19 Oct 2022