Plant Protection Quarterly Vol.23(1) 2008 29 Chrysanthemoides seed fl ies Three Mesoclanis spp. have been consid- Progress on boneseed (Chrysanthemoides monilifera ered for biological control of boneseed subsp. monilifera (L.) Norlindh) biological control: and bitou bush in Australia (Edwards and Brown 1997; Neser and Morris 1985). These the boneseed leaf buckle mite Aceria (Keifer) sp., the fl ies lay their eggs into Chrysanthemoides fl owerheads and the larvae can destroy lacy-winged seed fl y Mesoclanis magnipalpis Bezzi substantial proportions of developing and the boneseed rust Endophyllum osteospermi ovules, thus suppressing seed production. When introduced to Australia in 1996, the (Doidge) A.R.Wood bitou seed fl y (Mesoclanis polana Munro) (BSF) rapidly colonized almost the entire A B T.B. Morley and L. Morin range of bitou bush (Edwards et al. 1999). A Department of Primary Industries, PO Box 48, Frankston, Victoria 3199, However, in South Africa the BSF does not Australia. utilize boneseed and prevails at latitudes B CSIRO Entomology, GPO Box 1700, Canberra, ACT 2601, Australia. much closer to the equator than the more southerly bitou bush infestations in Aus- tralia. The BSF was therefore considered unlikely to effectively suppress seed pro- duction of Australian boneseed or the more Introduction stimulates dispersal. Dispersive mites can southerly bitou bush infestations, and this So far six exotic organisms have been re- walk to adjacent uncolonized shoot tips or appears to be true (Robin Adair personal leased in Australia as potential biological can be wind-dispersed to other boneseed communication and Morley unpublished control agents for the environmental weed plants. observations). Conversely, in South Africa boneseed (Chrysanthemoides monilifera sub- the lacy-winged seed fl y (LWSF) (Figure sp. monilifera (L.) Norlindh (Asteraceae)). Introduction to Australia 2) utilizes a range of C. monilifera subspe- None of these has established on boneseed Following host specifi city testing in South cies (Munro 1950, Edwards and Brown although one, the bitou tip moth (Comos- Africa in 2002 that showed the BLBM 1997) including boneseed, bitou bush tolopsis germana Prout (Lepidoptera: Ge- would be safe to introduce to Australia (most prosperously at latitudes similar to ometridae)) has colonized all of the major (Morley 2004), the mite was imported into southerly Australian bitou bush infesta- infestations of the closely-related invasive quarantine at the Department of Primary tions (Edwards and Brown 1997)), subsp. species bitou bush (C. monilifera subsp. ro- Industries – Frankston, Victoria in 2006 tundata (DC.) Norlindh). Currently three and was due for fi eld release in Spring organisms are under investigation for 2007. In collaboration with local land man- possible use as biological control agents agers, community groups and researchers, for boneseed. They are the boneseed leaf releases are planned for core boneseed in- buckle mite (Aceria (Keifer) sp. (Acari: Eri- festations in Victoria, South Australia and ophyidae)) (BLBM), the lacy-winged seed Tasmania and may be extended to New fl y (Mesoclanis magnipalpis Bezzi (Diptera: South Wales in the future. There are no Tephritidae)) (LWSF) and the rust fun- plans to release in Western Australia as gus (Endophyllum osteospermi (Doidge) very few boneseed infestations are present A.R.Wood) that induces witches’ brooms. and State law requires eradication of plants Figure 2. Lacy-winged seed fl y They are all endemic natural enemies of when found. Mesoclanis magnipalpis. boneseed in South Africa and each has the potential to suppress boneseed vigour and/or seed production. Boneseed Leaf Buckle mite Characteristics The BLBM (Figure 1) is vermiform (worm- like), about 0.15 mm long and its preferred host is boneseed (Morley 2004). The BLBM induces formation of leaf galls known as erinea. Erinea are composed of abnormally dense patches of hair-like structures that resemble felt. Initially erinea are white but turn brown within a few weeks. Erinea may develop anywhere on a leaf, have ir- regular shapes and size and may range from one to several hundred square mil- limetres. Erineum formation is induced by BLBM feeding at shoot meristems and commences before a leaf becomes visible. Erineum growth interrupts the normal ex- pansion of affected leaves, resulting in leaf disfi gurements ranging from small dim- ples to gross distortion of mature leaves. Figure 1. Boneseed leaf buckle mite Aceria sp. (Courtesy Charnie Craemer, The BLBM feeds and breeds in erinea un- Plant Protection Research Institute, Pretoria, and Alan Hall, University of til overcrowding or erineum deterioration Pretoria, South Africa). 30 Plant Protection Quarterly Vol.23(1) 2008 pisifera (L.) Norlindh and Chrysanthemoides sites has yielded nearly 4000 BSF (Morley should it be released in Australia, it is not incana (Burm.f.) Norlindh. Thus the LWSF unpublished data)). The reason for this expected to have a signifi cant impact on seemed a good candidate biological con- outcome is not known but the following most Australian bitou bush populations. trol agent. speculations seem plausible: Climate modelling has shown that the rust 1) LWSF is present but in such low num- would likely have its greatest impact in Failure of LWSF to establish bers that it has not yet been detected. If Tasmania and southern Victoria (Wood et Boneseed this is the case then further sampling al. 2004). Attempts to establish the LWSF in Aus- should eventually detect it. tralia have been in progress for nearly a 2) There are distinct biotypes of LWSF in Infection decade. It was fi rst released on boneseed South Africa that have particular Chry- E. osteospermi systemically infects its hosts in 1998 and also in 1999, 2000 and 2005. santhemoides preferences and LWSF ex via immature foliage and stems. After These efforts involved LWSF reared from C.m. pisifera is a biotype not suited to 1–2 years, infected plants develop witch- imported C. monilifera subsp. pisifera fruit the bitou bush populations found in es’ broom branches with multiple swol- using a special AQIS-approved direct re- Australia. Intraspecific variation of len stems, short internodes and smaller lease protocol to ensure the released in- Mesoclanis has not been studied but and slightly chlorotic leaves (Wood 2002, dividuals were free of pests and diseases. based on the experience described Wood and Crous 2005a) (Figure 3). The Releases were made in the You Yangs, on above and an observation by Munro rust produces fruiting bodies on leaves of the Mornington Peninsula and at Frank- (1950), biotypism seems a real pos- witches’ brooms when conditions are con- ston, Victoria. The LWSF did not establish sibility. Munro (1950) observed that ducive, generally in winter to late spring but on three occasions offspring were re- fl ies of a collection of M. magnipalpis (Wood 2002). covered in the same season as the release ex C. incana were ‘larger than usual’. (Aline Bruzzese and Robin Adair personal Importation of LWSF ex C.m. rotundata Impacts communications, Morley unpublished at a latitude comparable to Australia’s The rust has been shown to have a sig- data). This confi rmed the apparent suit- southerly infestations (e.g. St Francis nifi cant impact on boneseed populations ability of boneseed as a host for LWSF ex Bay, South Africa, where large popula- in South Africa, reducing growth and C.m. pisifera. The reason for establishment tions of LWSF can be found (Edwards reproduction and in some instances kill- failure is not known but it appears that and Brown 1997)) would address the ing plants (Wood 2002, Wood and Crous LWSF ex C.m. pisifera is not able to survive biotype theory. This could perhaps im- 2005a). Deformed infected branches of between the end of boneseed’s fruiting prove the chance of establishment on diseased plants produced far fewer buds, season in early summer and the beginning bitou bush and is the next most obvious fl owers and fruits than branches of healthy of the next fl owering season in late win- strategy to try. plants and usually die within 1–4 years. ter. In South Africa, LWSF ex C.m. pisifera 3) Competition with the BSF has prevent- The rust also has an indirect effect on the might not be constrained in this way either ed or impeded LWSF estab- because the interval between C.m. pisifera lishment. If this is the rea- fruiting and fl owering is suffi ciently short son for failure of the LWSF or there are alternative Chrysanthemoides to establish on bitou bush, (a) hosts whose fl owerheads are suitable and then it might be overcome available at critical times. Importation and by releasing larger num- release of the LWSF ex C.m. monilifera has bers and/or using other been previously considered but not at- techniques to promote es- tempted largely because boneseed’s rela- tablishment (e.g. exclusion tively short fl owering season combined of BSF from bitou bush at with the logistic and mandatory delays release points). of passage through Australian quarantine make this option diffi cult. Populations of Boneseed rust LWSF on C.m. monilifera are also often dif- The South African rust fungus fi cult to fi nd in South Africa (Robin Adair E. osteospermi is a microcyclic personal communication). Notwithstand- species only recorded on a ing these diffi culties, in light of the failure small group of related plants of LWSF ex C.m. subsp. pisifera to establish of the genera Chrysanthemoides on boneseed in Australia it might now be and Osteospermum (Calend- (b) worthwhile investigating the introduction uleae: Asteraceae) in South of LWSF ex. C.m. monilifera in case it exists Africa (Doidge 1926, Morris as a biotype specifi cally adapted to toler- 1982, Wood 1998, Wood and ate boneseed’s fl owerhead phenology. Crous 2005b). It is thought to have considerable potential Bitou bush for the biological control of In 2005, the LWSF ex C.m.