Research Note A survey of cossid attack in niten$ on the Mpumalanga Highveld of South Africa G. R. Boreham

Sappi Forests Research, Shaw Research Centre, P.O. Box 473, Howick, 3290 Email: [email protected]

SYNOPSIS

During July 2004, an infestation of an unknown larval in ten- year and older was reported on the Mpumalanga highveld of South Mrica. Samples of wood containing larvae were collected from the field and taken to the Forestry and Agricultural Biotechnology Institute, University of Pretoria. The adult specimens were subsequently identified by the Transvaal Museum as the native Coryphodema tristis. No records have been found ofthe insect on any member ofthe Myrtaceae. Atotal of approximately 3000 hectares ofE. nitens, within 95 compartments greater than eight years of age on the Mpumalanga Highveld were surveyed in September 2004. The older age classes and lower elevation sites had significantly higher infestations than the younger, higher elevation sites. Low infestations are present in young stands ofE. nitens « 6 years of age), and not restricted to lower productivity sites, an indication that the pest risk potential is higher than originally anticipated.

Keywords: Cossid moth, Euc. nitens, wood borer, Coryphodema

INTRODUCTION patersonii () (Taylor, 1957). Other host plants include the bush () (Picker During July 2004, the first signs ofinfestation by an et al., 2002), and other exotic ornamentals such as unknown insect in teh- year and older Eucalyp• oak, elm and hawthorn (Annecke & Moran, 1982). tus nitens compartments were reported by foresters Eight host plant records from the families , on the Mpumalanga highveld of South Africa. , Malvaceae, Myoporaceae, Scrophula• Subsequently, a detailed survey was conducted to riaceae, and are listed in Kroon, determine the severity and extent ofthe infestation. (1999). C. tristis has a wide natural distribution This research note briefly reviews the current throughout the country (Picker et al., 2002). No understanding ofthe insect and summarizes some of records have been found ofthe insect on any member the findings ofa field survey conducted to assess the ofthe Myrtaceae. impact of the insect pest. Eucalyptus nitens was traditionally grown for Initially, the infestation onE. nitens was thought mining timber in the cold, high altitude, summer to be due to Phoracantha semipunctata, a common rainfall areas ofthe Highveld ofSouth Mrica. During insect pest in South Mrica, which infests Eucalyptus the course of the past decade, this species has been trees suffering from moisture stress. Samples of more widely planted due to its desirable pulping wood containing larvae were collected from the field properties, and aboveaverage paper properties (Swain and taken to the insectary at the Forestry and & Gardner, 2003). The total area established to Agricultural Biotechnology Institute, University of E. nitens in the Highveld region is estimated to be Pretoria, and placed in emergence chambers to allow approximately 25000 hectares. Coryphodema tristis adults to develop. The adult specimens were could thus have a significant impact on this sector of subsequently identified by the Transvaal Museum the forest industry, specifically for those markets as the native Coryphodema tristis (Drury) that are dependant on E. nitens and its associated (: ) (Gebeyehu, et al., 2005). products. The aim of this study was to assess the Coryphodema tristis, known as the borer, is impact of C. tristis in plantations ofE. nitens on the polyphagous and some of its food plants include Mpumalanga Highveld. Pyrus (pear), Malus sylvestris (apple), and Cydonia vulgaris (quinceHMeyer, 1965). Ithas also MATERIALS AND METHODS been recorded on loquats, olives, vines, Buddleia and Melia azedarach (Syringa) (Brain, 1929;Annecke & A total of approximately 3000 hectares ofE. nitens, Moran, 1982), and avocado (Hoppner, 1994). The within 95 compartments greater than eight years of larvae have also been found in the stems ofLagunaria age on the Mpumalanga Highveld (25°44' S to

Southern African Forestry Journal- No. 206, March 2006 23 26°30' S) were surveyed in September 2004. The an area weighted mean infestation of 9.6% for the ages ranged between 8.3 and 15.8years. The number entire survey area. ofinfected trees were counted within a pre-determined The age and altitude classes were used in the fixed number of transects following a zig-zag pattern model and plots were used in the random model. The across each compartment. Transects were distributed results of the REML analysis are shown in Table 1. evenly across each compartment to ensure full representation. Asingle transect comprised 100 live TABLE 1. Summary of the results using REML trees and the number oftransects per compartment Variance Components Analysis. was proportionate to the planted area ofthe stand (a minimum of one transect and a maximum of 5 Variable<0.001Chi-sqd.f.121 104.91Wald33.53156.5prob transects per compartment). Compartmentsstatisticthat were Altitude class Altitude less than one hectareAgeAgewereclassclassexcludedx from the survey. The criteria used to determine whether a tree was infested were the presence ofboring dust on the stem or on the forest floor around the base of the tree. After the survey, a field inspection was performed to ascertain whether C. tristis had infested any other Eucalyptus species, younger age-classes ofE. nitens or any of the Pinus species planted in this region. This inspection was necessary to obtain an initial Some of the results are confounded by the indication ofthe host range ofthe pest amongst the unbalanced survey data, a consequence of the commercial species grown in the region and also to sampling. The older age classes had significantly determine the levels ofinfestation inE. nitens stands higher levels of infestation than the younger age younger than 8 years of age. Compartments for the classes. Compartments that fell within the lower inspection were identified after the survey and only elevation class had significantly higher infestation those that were adjacent to or in close proximity to than the higher elevation sites. There were no infestedE. nitens compartments were selected. significant differences in infestation levels between Site index is defined as the dominant height ofan the high and the low productivity sites. The index tree species measured at a fixed reference age. classification of compartments as either off-site or The reference age used for E. nitens was 5 years. In on-site was also significant, mostly being driven by order to rate the growth capability (productivity) of altitude as opposed to site productivity. Planted a site in terms of round wood production, the actual compartments had higher infestations than site index values, derived from enumerations, were compartments that had been coppiced, but this could used to classify each stand as either high (>14m) or be explained by the fact that 82% of the coppiced low (::;;14m)productivity. Each compartment was compartments fell within the higher altitude classified as either high elevation (~ 1600m) or low (~ 1600 m) sites. This is understandable as elevation « 1600m) based on the actual altitude of historically the better performing sites would have each compartment, as well as the age (~ or < 12 been coppiced and the poorer sites re-established by years) ofthe stand. Compartments were also classified planting. There was no other evidence to suggest by the establishment method as either planted or that planted compartments were at higher risk to coppiced. Compartments were considered as either infestation than compartments that were re• on-site if established on a high productivity site with established by coppicing. The actual mean annual an altitude over 1600 m or off-site if established on rainfall recorded over the 4-year period prior to the a low productivity site below 1600 m. Long term survey ranged between 3% and 17% below the long rainfall data (prior to August 2000) were compared term average for this region. against the actual4-year mean rainfall recorded by The survey data has been summarized in Table 2, three plantation offices in the region from July 2000 with the individual cells ofthe matrix containing the to June 2004. These data were used for comparative predicted mean number ofinfested trees per 100 live purposes only. trees together with the number of observations To produce an efficient analysis ofthe unbalanced (transects) surveyed. The overall trend was towards survey data the individual compartment plots were higher infestation levels in the older age classes on analyzed with the Residual Maximum Likelihood sites with altitudes below 1600 m. (REML) method using the Genstat Version 7 The results of the post-survey field inspection Statistical Software package. indicated that Eucalyptus dunnii, E. fastigata, E. macarthurii andE. smithii are not currently infected RESULTS by C. tristis. There were however very lowinfestation levels «1%) in some E. nitens compartments less The number of infested trees were counted and than 8 years of age (a total of 7 of the 11 stands expressed as a percentage ofthe total number oflive inspected had very low infestation levels). Neither trees assessed within each transect. The actual Pinus patula nor P. elliottii were infested by the infestation levels ranged between 0% and 77% with pest.

24 Southern African Forestry Journal- No. 206, March 2006 TABLE 2. Table of predicted means for the number commercial eucalypt species, and seed production of infected trees by altitude and age class. improves as the age of trees reaches 10-12 years (Poynton, 1979). The results ofthis survey indicate that C. tristis is a direct threat to the seed orchards .Age (years) used for commercial seed production in this region of Altitude (m) < 12 ~ 12 South Mrica. C. tristis has infectedE. nitens stands over a wide ~ 1600 1.9 2.9 (n=80) (n=123) geographic area of the Highveld region, and mean infestation levels are high in some stands. Although <1600 1.2 27.5 at very low infestation levels, C. tristis is present on (n=18) (n=83) higher productivity sites and in stands younger than 8 years of age. Older trees are more at risk and this is aggravated on lower elevation sites. These factors, DISCUSSION together with the below average rainfall in the region over the past four years, have all contributed towards It is not uncommon for indigenous pests to move the high levels ofinfestation. Little is known regarding across to exotic plantation hosts. The association of the rate of spread and dispersal capabilities of valdiviana, a native cossid moth of C. tristis within a commercial plantation environ• Chile, withE. nitens indicates the adaptability ofthe ment. In Chile, C. valdiviana often re-infests the cossid moth to a foreign host plant (Kliejunas, et al., same tree, which suggests a slower rate of spread 2001). Like C. tristis, the Chilean cossid moth has a and C. tristis is known to re-infest the same vines in preference for E. nitens, and is only occasionally the Western Cape. The presence of C. tristis in an found in E. gunnii and E. camaldulensis. It is isolated 25 year old E. nitens seed orchard with a interesting that its association with E. nitens in large buffer of surrounding pine (Boreham, Chile is fairly recent and the large scale afforestation unpublished) suggests that the dispersal capabilities with eucalypts (including E. nitens) commenced in of the insect may be fairly good. the 1980's which is similar to the period of The open larval galleries of C. tristis provide establishment ofthis species on a wider scale in the potential entry points for stain and decay fungi and Highveld region of South Mrica. other pathogens. However, tree mortality is not E. nitens has been grown commercially on the evident directly after C. tristis infestation and there Highveld region for at least 25 years and the reasons does not appear to be an association between the for the sudden host switch are not fully understood. insect and harmful microbes. A major portion ofthe C. tristis has not infested Pinus elliottii, P. patula life cycle is spent in the larval stage within the stem or any ofthe other cold-tolerant Eucalyptus species or branches and the harvesting of heavily infested and has not been reported on the E. grandis x stands together with controlled burning of the E. nitens hybrids grown in this region (Da Costa, remaining debris may be an effective short term 2005,pers. comm.).Many other coldtolerant eucalypt measure to help reduce C. tristis population numbers. species have been grown commercially in this region Monitoring oftemporal changes in both distribution for longer periods than E. nitens and C. tristis has and severity of C. tristis over the region in which it apparently not infested any of these species. This currently occurs will assist in understating the recent host association of C. tristis with E. nitens population dynamics ofthe insect. Such data will also has been localised, sudden and specific. The distri• provide the industry with information to develop a bution of C. tristis coincides with the major timber strategy forthe future control ofthe insect. Arepetition growing areas of South Africa (Picker et al., 2002), ofthe survey presented in this study on a larger scale yet there have been no confirmed reports ofthe insect is planned for the future and this will hopefully also in E. nitens in the cool temperate areas ofKwaZulu promote a better understanding ofthe pest. Natal. Due to its polyphagous nature, C. tristis could begin to infest other commercial eucalypt REFERENCES species. During the winter of2005, infestations were not ANNECKE, D.P. and MORAN, V.C., 1982. and Mites of cultivated plants in South Africa. Butterworths. pp382. restricted to sub-dominant trees but were also found DA COSTA, D., 2005. Mondi Business Paper. Personal in the dominant and more vigorous individuals in communications. stands (Boreham, unpublished). This confirms that BRAIN, C.K., 1929. Insect pests and their control in South Africa. Die Nasionale Pers Beperk. pp223. infestations are not restricted to stressed trees as GEBEYEHU, S., HURLEY, B.P. and WINGFIELD, M.J., 2005. was initially suggested. The absence or low level of A new lepidopteran insect pest discovered on commercially natural enemies has resulted in high levels ofC. tristis grown Eucalyptus nitens in South Africa. South African Journal of Science 101. January/February 2005. p26. within infested trees. Likewise, the fact that large HOPPNER, G.F.J, 1994. The Trunk Borer of Grapevines. numbers of both early and late larval stages are Wynboer, July 2004. p14. KLIEJUNAS, J.T., TKACZ,B.M., BURDSALL,H.H., DENITIO, present on these sites indicates that the insect has G.A, EGLITIS, A., HAUGEN, D.A. and WALLNER, W.E., become well established. E. nitens produces low seed 2001. 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Southern African Forestry Journal- No. 206, March 2006 25 from South America. General Technical Report FPL-GTR• POYNTON,R. J., 1979.Tree planting in South Africa. Volume 2. 124. United States Department ofAgriculture, Forest Service, THE EUCALYPTS. Department of Forestry. Republic of Forest Products Laboratory. pp134. South Africa. KROON, D.M., 1999. Lepidoptera of Southern Africa: Host• SWAIN, T.L. and GARDNER, RAW., 2003. A summary of plants and other associations. A Catalogue. Lepidopterists' current knowledge of cold tolerant eucalypt species (CTE's) Society of Africa. pp160. grown in South Africa. ICFR Bulletin 03/2003. Institute for MEYER, A.J., 1965. A histololrtcal study of the alimentary canal Commercial Forestry Research, Pietermaritzburg, South and associated structures in the larvae of Coryphodema Africa tristis Drury. Lepidoptera. M.Sc Thesis, University of TAYLOR,J.S., 1957. Notes on Lepidoptera in the Eastern Cape Stellenbosch. Province (Part IV). Journal of the Entomological Society of PICKER, M., GRIFFITHS, C. and WEAVING, A., 2002. Field South Africa. Volume 20(2). p315. guide to Insects of South Africa. Struik. pp440.

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