Forest and Timber Insects in New Zealand No. 10. Eucalyptus tortoise beetle. Based on J. Bain 1977

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1 Forest and Timber Insects in New Zealand No. 10 Eucalyptus tortoise beetle Based on J. Bain 1977 Insect: Paropsis charybdis Stål (Coleoptera: Chrysomelidae) Fig. 1 Eucalyptus tortoise beetle. Type of injury Feeding by adults and larvae of Paropsis charybdis gives leaves of eucalypts a scalloped appearance (Fig. 2). The larvae prefer the young foliage and shoots, but the adults are less selective and can be found feeding on older foliage as well. Heavy defoliation causes the tops of trees to have a scruffy appearance with many bare twigs (Fig. 3). Repeated defoliation may cause the death of the tree. Ent 10 Paropsis charybdis.doc Page 1

2 Fig. 2 Feeding by adults and larvae of the eucalyptus tortoise beetle gives eucalypt leaves a scalloped appearance. Hosts Nearly all species of Eucalyptus grown in New Zealand are defoliated to some extent by this tortoise beetle but E. globulus, E. viminalis, and E. macarthurii are the commonest of the mostfavoured hosts. There is great variation in the susceptibility of different eucalypt species, and generally the hosts can be divided into three groups according to how often and how severely they are defoliated. Ent 10 Paropsis charybdis.doc Page 2

3 Fig. 3 - Trees defoliated by the eucalyptus tortoise beetle. Group I eucalypts are liable to severe defoliation over one or two seasons in any 3-year period: E. deani, E. globulu, E. leucoxylon, E. macarthurii, E.resinifera, E. viminalis. Group II eucalypts are liable to defoliation in at least one season in any 5-year period: E. amplifolia, E. botryoides, E. fastigata, E. gunii, E. maidenii, E. obliqua, E. ovata, E. pauciflora, E. punctata, E. radiata, E. saligna. Group III eucalypts are species liable to only slight or negligible defoliation by this insect, with perhaps one season of obvious defoliation in 10 years. This group includes nearly all the species grown in New Zealand not included in Groups I and II. Exceptions to these groupings occur. Site factors, seed source and silviculture can have an effect on a tree's susceptibility, e.g., in the Rotorua-Tokoroa area E. radiata (Group II) often suffers Group I defoliation, and E. nitens (Group III) has been recorded to suffer Group II defoliation. Distribution Paropsis charybdis is an Australian insect and was first recorded in New Zealand from the Port Hills, Christchurch, in It is now found throughout New Zealand except for the upper Waiau Valley, southern Westland, and Stewart Island. In Australia it is a rare insect, but whether this is because of competition with other species of Paropsis or because of a high rate of parasitism has not been established. Economic importance This insect is regarded as the most serious defoliator of eucalypts in New Zealand. Frequent and severe defoliation of E. globulus, E. viminalis, and E. macarthurii has virtually curtailed the planting of these species. Description, life history, and habits The beetle, which is 8-14 mm long, is stout and strongly convex and has a distinct tortoise-like shape. It varies from straw-coloured to reddish-brown, with darker marks on the back (Fig.1).The fully grown larva (Fig.4) is usually yellowish but sometimes pinkish, is covered with Ent 10 Paropsis charybdis.doc Page 3

4 black spots, and has a dark stripe running down each side. When disturbed or alarmed the larva extrudes a pair of horn-like processes from near the rear end and ejects a strong-smelling spray. Fig. 4 - Larvae of the eucalyptus tortoise beetle. The only other insect which might be confused with Paropsis charybdis is a second Australian tortoise beetle, Trachymela sloanei (Blackburn), first found in New Zealand in 1976, and which occurs on eucalypts in Auckland city and suburbs. The adult Trachymela sloanei is 6-8 mm long, dark brown, and covered with a fawn, flour-like dusting. Both adults and larvae feed at night, and during the day hide under loose bark. There are two generations of Paropsis. charybdis per year. About August-September overwintering adults emerge and, after spending some time feeding and mating, they lay eggs (Fig.5) usually in groups of on the undersides of leaves near the newly flushed foliage. These eggs hatch in 2-3 weeks and the young larvae feed in groups on the new shoots. The larger larvae are usually found singly on both old and new foliage. About November-December the mature larvae drop to the ground and pupate in the soil. When the new adults emerge in about 2 weeks this cycle is repeated. Adults produced by the second generation feed for a short while and then hibernate under loose bark or in the leaf litter until the following spring. Ent 10 Paropsis charybdis.doc Page 4

5 Fig. 5 - Eggs of the eucalyptus tortoise beetle. Control Chemical control by the aerial application of an insecticide, such as DDT, is successful in controlling Paropsis charybdis. However, only short-term control can be expected as the insecticide does not prevent re-infestation from outside areas or from the second generation. Control by biological agents, especially other insects, offers some hope and during the summers of and tachinid flies belonging to the genera Froggattimyia and Paropsivora, parasitic on Paropsis charybdis, were imported from Australia for study. Releases of one species, Froggattimyia tillyardi, were made in 1975 but it is unlikely to have become established. As mentioned previously, some species of eucalypts are far less susceptible to defoliation than others. It should be possible to minimise the damage caused by the beetle by planting unpalatable species such as E. lastigata, E. delegatensis, and E. regnans. References Bain, J. 1977: Paropsis charybdis Stål (Coleoptera: Chrysomelidae). Eucalyptus tortoise beetle. New Zealand Forest service, Forest and Timber Insects in New Zealand No. 10. Baker, R.T. and de Lautour, R.B., Control of the tortoise beetle by aerial spraying with DDT. Farm Forestry 4: Clark, A.F., Paropsis dilata Er. in New Zealand. New Zealand Journal of Science and Technology 12: Clark, A.F., A survey of insect pests of eucalypts in New Zealand. New Zealand Journal of Science and Technology Styles, J.H., Notes on the biology of Paropsis charybdis Stal (Coleop- tera : Chrysomelidae). New Zealand Entomologist 4 (3): White, T.C.R., The establishment, spread and host range of Paropsis charybdis Stål (Chrysomelidae) in New Zealand. Pacific insects 15: Compiled: 1977, limited revision Ent 10 Paropsis charybdis.doc Page 5