26 South African Journal of Science 101, January/February 2005 Research in Action Coryphodema tristis on E. nitens A new lepidopteran insect pest Coryphodema tristis was observed only on E. nitens and none of the surrounding discovered on commercially grown compartments of other Eucalyptus species was affected. E. nitens infested with C. Eucalyptus nitens in South Africa trisits in the Lothair/Carolina area ranged from 8 to 13 years of age. The infested sites were visited in July, when only the larval *† * Solomon Gebeyehu , Brett P. Hurley and stage of C. tristis was observed, and in Michael J. Wingfield* August, when the larval stage was still dominant, but pre-pupae and pupae were also observed. Extensive larval NTENSIVELY MANAGED EUCALYPTUS A new pest discovered tunnels in the main stems and branches of Iplantations form an important component During the early part of 2004, very the trees were observed. Frass, resulting of the South African forestry industry. In serious damage was noted on E. nitens in from the tunnelling, accumulated on the this paper we identify and comment on a the Lothair/Carolina area, Mpumalanga tree surrounding the point of entry and wood-boring moth (Lepidoptera: Cossidae) province, South Africa. Damage was on the ground surrounding the tree recently discovered damaging Eucalyptus (Fig. 3), making the presence of the insect nitens clearly due to a wood-boring insect that trees in plantations growing in the quite conspicuous. Lothair/Carolina area. Infestedwoodcontain - resulted in extensive tunnelling in the wood. It was evident that eggs were laid ing larvae was incubatedin emergence cham - Cossid moths bers for two months. Upon emergence, adult on the bark of the main stems or branches, moths were collectedandidentifiedas and soon after hatching early instar larvae Members of the family Cossidae have Coryphodema tristis. This insect is native to began to feed on the cambium. a worldwide distribution, and they are South Africa andis well known as a pest of As the larvae grew, they tunnelled into represented by several genera and species. fruit trees andvines as well as of a few native the sapwood and hardwood (Fig. 1), mak- In South Africa, the family is represented E. nitens 8–10 trees. Its presence on appears to ing extensive galleries and pushing frass by over 100 species. Cossid larvae are represent a sudden new host association, to the outside of the stems, which makes known to infest several families of hard- which is of significant concern to South 11 their presence easy to detect (Fig. 2). wood species including timber trees, African forestry. Research on the biology, orchard trees and garden shrubs.5,7 phenology, population dynamics and The larvae were clearly lepidopteran Coryphodema tristis adults in South possible hosts of origin in the Lothair/ and all indications based on the juvenile Carolina area is currently under way. The forms were that they were of moths Africa have rudimentary mouthparts, possibility of using natural enemies to reduce belonging to the family Cossidae. Species- they do not feed and they live for a the impact of this pest is also being consid- level identification required that adult maximum of six days, during which they ered.mm insects be obtained. Thus, samples of the lay eggs. One female can lay from 104 to wood containing larvae were collected 316 eggs. The adult moths are rarely seen, Introduction from the field and brought to the owing to their inconspicuous dull colour Intensively managed eucalypt planta- insectary at the Forestry and Agricultural (Fig. 4) and the brief duration of the adult tions form the basis of the forestry indus- Biotechnology Institute, University of stage. The wing expansion of both sexes try in South Africa. Of the 1.4 million Pretoria, and placed in emergence cham- varies from 4 to 7 cm, depending on the size of the branch or stem in which the hectares of plantations in the country, bers to allow adults to develop. larva has fed.5 about 700 000 ha are planted to eucalypts. Adult emergence began in the first week C. tristis The most important Eucalyptus species of September, eight weeks after logs The larvae of are a transparent, whitish colour with two reddish, rather grown include E. nitens, E. grandis and hy- containing larvae were brought to the broadly separated, irregular lines extend- brids of these species with each other and, insectary, and emergence continued for three weeks. Adult specimens were then ing along the middle of the back from the for example E. urophylla, E. camaldulensis submitted to the Transvaal Museum for 2nd to the 12th body segment (Fig. 5). An and E. dunnii.1,2 identification. The moth was subsequently indistinct broad line extends along the Variousinsect pests are found on Eucalyp- identified as the native Coryphodema tristis middle line of the back between the two tus in South Africa and some cause serious (Drury) (Lepidoptera: Cossidae). reddish lines from the 2nd to the 6th body damage. Perhaps the most damaging in Coryphodema tristis is well known in segment. Laterally, there are obscure, the country has been the eucalyptus South Africa and is most commonly small, irregular broken reddish markings Gonipterus scutellatus snout beetle, referred to as the quince borer. The moth on the body. The head is broader than the Gyllenhal. Both adults and larvae of this derives its common name from the quince rest of the body and brown in colour, with insect feed on the leaves and buds of their tree, with which it is closely associated in darker brown eyes and jaws.5 The fully- hosts and they can cause extensive defoli- the western and southwestern Cape. In grown larvae range in size from 2–4 cm, 3,4 ation of susceptible trees. However, this region, it is an economically impor- depending on the size of the stems on when one considers the great number of tant pest on many fruit trees including which they have fed. insect pests known on Eucalyptus species quince, grape vines, apples and sugar The biology of cossids is variable, but in their native range, South African pears.5,6 C. tristis also feeds on a wide most species take 1–3 years to complete forestry has, thus far, been relatively range of native and exotic trees, including their life cycle. Petty5 studied the biology fortunate in not having been particularly species in the families Ulmaceae, Vitaceae, of C. tristis and showed that the insect seriously affected by insect pest problems. Rosaceae, Scrophulariaceae, Myoporaceae, takes two years to complete its life cycle. Malvaceae and Combretaceae.7 This is, The greater part of its life history (up to *Forestry and Agricultural Biotechnology Institute (FABI), however, the first record of C. tristis eighteen months) is spent in its larval University of Pretoria, Pretoria 0002, South Africa. †Author for correspondence. attacking Eucalyptus or any other species stage. In the Western Cape province, the E-mail: [email protected] of Myrtaceae in South Africa. emergence of adults occurs from October Research in Action South African Journal of Science 101, January/February 2005 27 to mid-December. This is not very different from our observations of the insect on Eucalyptus. On infested E. nitens trees in Lothair/Carolina, the insect was in its larval stage in July, when it was first observed, and adult emergence began in the insectary in September. Further observation in October in the field re- vealed that all stages could be found at this time of the year. We observed early to late instar larvae, pupae as well as evidence of recent adult emergence such as pupal cases protruding out of the emergence holes on the trees (Fig. 6). Adults were not seen. Future prospects At this stage, there are several questions requiring answers in order to manage this new Eucalyptus pest in South Africa. The factors surrounding the sudden new host association of the moth with a plantation Eucalyptus are unknown. In Chile, where Eucalyptus is planted as an exotic in plan- tations, the native cossid moth Chilecomadia valdiviana feeds naturally on Salix chilensis and other native forest trees. In that situation, it has also acquired a new host association with E. nitens and a few other commercially grown Eucalyptus species.12 As yet, we can only speculate on the reason why C. tristis has infested E. nitens. Considering the large number of infested trees, it is unlikely that the oviposition of C. tristis on E. nitens is merely by chance. It is more probable that C. tristis was specifi- cally attracted to E. nitens. The infested sites were generally compartments of stressed trees, which suggests that the moths could possibly have been attracted by kairomones or other stress signals. Whatever the cue, the surrounding com- partments of different eucalypt species did not share this, as none of these com- partments was infested with C. tristis. Figs 1–6. 1, Tunnels made by Coryphodema tristis larvae; 2, frass, from C. tristis tunnelling, pushed out the tree; 13 The ‘enemy-free space’ hypothesis 3, frass from C. tristis on the forest floor; 4, C. tristis adult; 5, C. tristis larvae; 6, C. tristis pupal casing protruding could also explain the newly acquired from emergence hole in tree. oviposition behaviour of C. tristis. Here, association with new hosts by phyto- such as Australia, the United States and these large, emerging populations of C. tristis phagous insects may have its origin based Italy, where some cossid species have in the plantations might result in in part in securing enemy-free space.14,15 been known as serious pests of forest and the insect ovipositing on more healthy E.