72 Plant Protection Quarterly Vol.26(2) 2011 Mechanical and chemical control tech- niques are utilized to suppress P. myrtifo- Phytophagous organisms associated with the woody lia, but are generally only successful when shrub Polygala myrtifolia (Polygalaceae) and their applied to small areas where regular fol- low-up treatments can be implemented. potential for classical biological control in Australia In Australia, few phytophagous arthro- pods occur on P. myrtifolia, and herbivory Robin J. AdairA,D, Stefan NeserB and Val StajsicC damage is low to negligible. Low herbivo- A Department of Primary Industries, Bioprotection Research Division, ry pressure in Australia may contribute to PO Box 48, Frankston, Victoria 3199, Australia. the success of P. myrtifolia as an environ- B Plant Protection Research Institute, Agricultural Research Council, mental weed. In contrast, phytophagous species can cause substantial damage to Private Bag, X134, Pretoria 0001, South Africa. C P. myrtifolia in South Africa, and several National Herbarium of Victoria, Royal Botanic Gardens Melbourne, species have potential for classical biolog- Birdwood Avenue, South Yarra, Victoria 3141, Australia. ical control (Adair and Neser 1996). Al- D LaTrobe University, Bundoora, Victoria 3086, Australia. though P. myrtifolia has not been formally accepted as a target for biological control in Australia, this form of suppression is considered the only effective long-term Summary management option. Coastal ecosystems in southern Australia in Adelaide in 1845 (Carter et al. 1990). In this paper, the phytophagous biota have been invaded by the South African The first presumed wild collections of associated with P. myrtifolia and their po- shrub Polygala myrtifolia L. (Polyga- P. myrtifolia in Australia were made in New tential for biological control are discussed laceae), leading to ecological disruptions South Wales at Hastings River between with an emphasis on potential impact on and loss of biodiversity. Expansion of P. 1856 and 1862 (MEL 2244752), followed plant health and possible conflicts of inter- myrtifolia populations is expected unless by a collection in Victoria between Bright- est with horticultural industries. A com- effective containment or suppression ac- on and Mentone in 1886 (MEL 2120881). parison of herbivory levels on P. myrtifolia tivities are implemented. Low herbivory Polygala myrtifolia is now naturalized in South Africa and Australia is made. pressure in Australia compared to the across southern Australia with extensive species’ native range is likely to have infestations present in Victoria around Methods contributed to the invasion success of P. Melbourne and in South Australia on the Survey for phytophagous species myrtifolia. Twenty-eight phytophagous Eyre Peninsula. Isolated and expanding Sampling of phytophagous organisms and organisms are recorded from P. myrtifo- populations are widely scattered in coastal pathogens associated with P. myrtifolia lia in South Africa and six have potential New South Wales, eastern Tasmania and and other Polygalaceae was undertaken as classical biological control agents, but south-west Western Australia (Figure 1). between 1996 and 2003 at 41 sites in South require formal host specificity and im- Dense infestations of P. myrtifolia disrupt Africa, most of which were in the Western pact evaluation. Further understanding ecological processes in native coastal veg- Cape (Figure 2). Most sites were sampled of seed-bank dynamics and recruitment etation and threaten biodiversity values. once, usually in the spring–summer period. patterns of P. myrtifolia in Australia would contribute to the selection of suit- able biological control candidates. Seed- destroying agents were not found on P. myrtifolia in South Africa, but additional survey effort is warranted as seed-de- stroying agents could alleviate conflicts of interest between environmental pro- tection and the ornamental garden trade. Introduction The South African shrub Polygala myrtifo- lia L. (myrtle-leaf milkwort) occurs natu- rally in a broad range of vegetation asso- ciations distributed across the coastal and near-coastal belt of southern South Africa extending into mountainous areas of KwaZulu-Natal (Drakensberg) and Lesot- ho and the north-western Western Cape (Bokkeveld Mountains). The species is morphologically highly variable and sev- eral infraspecific taxa have been described (Harvey 1860, Bredenkamp 2000). Polygala myrtifolia is a popular garden ornamental in South Africa, and is also widely used for horticultural purposes in other temper- ate climates, particularly Australia, New Zealand, USA and southern Europe (Esler 1988, Cervelli 2001, Meerow and Ayala- Silva 2005). In Australia, the earliest record Figure 1. Australian distribution of Polygala myrtifolia based on Australia’s of P. myrtifolia is from nursery catalogues Virtual Herbarium (2011) records. Plant Protection Quarterly Vol.26(2) 2011 73 At a survey site, plants from the Polyga- laceae were haphazardly chosen and visu- ally searched for the presence of damaging species. Most survey sites were selected where P. myrtifolia was the dominant poly- galaceous species present. Other species included in the survey were: P. fruticosa P.J.Bergius., P. teretifolia L.f., P. peduncu- laris Burch. ex DC., Polygala myrtifolia var. pinifolia (Lam. ex Poir.) Paiva, P. sp. (la- belled as P. empetrifolia Houtt.), Muraltia heisteria (L.) DC. and Nylandtia spinosa (L.) Dumort. Where damage symptoms were evi- dent, stems, twigs or roots were dissected for evidence of phytophage activity and suspected causative agents were collect- ed. Sweep netting and beating were also utilized in instances where bushes were dense and difficult to search visually. Buds, flowers, fruits and seeds were col- lected, if available, and dissected for phy- tophagous organisms. Adult arthropods were collected, preserved and deposited with the South African National Insect Collection (Plant Protection Research In- Figure 2. Distribution of Polygala myrtifolia in South Africa (shaded) and location stitute – Agricultural Research Council of survey points () for phytophagous organisms. (PPRI-ARC), Pretoria) for identification. Mycological specimens were deposited with PPRI (Stellenbosch). If immature 2–4 plants of P. myrtifolia. Buds, flowers as food sources by the greatest number of arthropod specimens were present, these and fruits were counted to give a measure organisms with eight and seven species, were reared to adults in the laboratory us- of inflorescence size, and all floral units respectively. The only pathogenic fungus ing the same host taxa that they were col- were dissected for evidence of herbivory. found on P. myrtifolia was Uredo polygalae lected from in the field as a food source. Shed floral structures were also counted Kalchbr. which forms pustules on mature To increase the extent of the survey, all and were recognized by the presence of leaves. sheets of Polygala and Muraltia held at small bracteoles on the raceme rachis. the Compton Herbarium, South African Data from Australian and South African Herbivory levels National Biodiversity Institute (SANBI), collections of P. myrtifolia were compared The mean number of flowers produced Kirstenbosch were examined for evidence using a Students t-test assuming unequal on racemes, the level of floral abortion, of phytophage symptoms. Host and phy- variance to determine differences between number of seeds produced per capsule, tophage data were collected where clear means. Percentage data was arcsine trans- and leaf size were not significantly differ- identifications of phytophages could be formed before analysis. ent between Australian and South Afri- made. can populations of P. myrtifolia (Table 3, Results 4). However, leaf and inflorescences her- Comparison of herbivory levels between Location of survey sites bivory levels of P. myrtifolia populations South Africa and Australia Survey sites for phytophagous species in South Africa were significantly higher In 1996, 15 sites in the Western Cape, were located across the distribution of P. than in Australian populations. Although South Africa and 12 sites in south-eastern myrtifolia, with 32 out of 41 sites present mean leaf herbivory levels were 0.1% in Australia, were sampled for herbivory lev- in the Western Cape, the centre of distri- Australian populations, low herbivory els by haphazardly collecting 20–25 leaves bution for P. myrtifolia (Table 1). Plants of levels (3.3%) were also recorded for South from the canopy of 2–5 plants of P. myrti- P. myrtifolia were found in a range of habi- African populations. No seed herbivory folia. Sites in South Africa were sampled tats from coastal strandveld, usually on was detected in Australian and South Af- in January and February, and Australian rocky outcrops close to the high tide mark rican populations of P. myrtifolia (Table 3). sites were sampled mostly in February and (Figure 3a), macchia and coastal macchia, March. Leaves were pressed and air-dried. renosterveld and mesic succulent thicket. Discussion Leaf damage levels were determined by Polygala myrtifolia var. grandiflora Hook. Australian populations of P. myrtifolia are scanning leaves with an ADC Area Meter (see Curtis 1837) occurs naturally in coast- subject to very low levels of leaf, flower (Bioscientific Ltd), and calculating leaf area al vegetation of southern South Africa, and seed damage. Stem and root her- removed from entire individual leaves. particularly in the Knysna region, and was bivory