News 81N General News Mimosa Leaves Niche for of fungal pathogens, and it has been the task and would further reduce the degree of New Agents of the biocontrol programme to select the shading beneath stands, whilst also reducing most promising of these and screen them seedling regeneration, hastening the A leaf-feeding geometrid moth, Macaria for introduction. Eleven insect and two replacement of mimosa with native vegeta- pallidata (= Xenoecista pallidata), released pathogen species have been released to date tion. in Northern Territory in September this [see also BNI 20(1), 6N-7N (March 1999), A chrysomelid beetle (Malacorhinus irreg- year is the latest in a long line of biocontrol Preventing wetland wipe-out]. ularis) from Mexico was one such candi- agents introduced into Australia against One agent, the leaf-beetle Chlamisus date. It has an adult leaf-feeding stage, but Mimosa pigra (mimosa or giant sensitive mimosae (introduced in 1985), only estab- its soil-dwelling larvae feed on various plant). In addition to the promise this agent lished on one river system and has had only plant parts, particularly seedlings and ger- holds, encouraging results reported for pre- minimal impact on mimosa. The impacts of minating seeds. Adult beetles were shown viously released agents suggest that the sus- a flower-feeding weevil (Coelocephalapion to prefer young, growing leaves. For larvae, tained biocontrol programme against pigrae, introduced in 1994) and a seed- survival to adult was best on seedlings, with mimosa is paying off. feeding bruchid (Acanthoscelides puniceus, the cotyledons preferred by all larval Mimosa currently occupies some 850 km2 introduced in 1983), which are widespread stages. By consuming leaves the adults of wetlands in Northern Territory and and sometimes abundant, are currently reduce the vigour, growth rate and seed threatens a great deal more. It has been being assessed. However, two stem-boring production of the plant, while by con- found recently for the first time in Queens- moths (a gracillariid (Neurostrota gun- suming seedlings the larvae reduce stand land, about 2000 km from the nearest infes- niella) and a sesiid (Carmenta mimosa) first regeneration. This ‘double-barrelled’ tation. Its potential distribution extends released in 1989) are undoubtedly the most strategy meant the potential for added from the north coast of Western Australia successful to date. Neurostrota gunniella impact from introducing this species was across the country and down as far as dispersed rapidly and is abundant in many great. locations. Carmenta mimosa is spreading northern New South Wales. Mimosa pigra Host-specificity testing on 82 plant species more slowly, but is already widespread on was declared one of Australia’s 20 Weeds showed that larvae survived and completed two river systems and firmly established on of National Significance in 1999. It has development only on Mimosa pigra (on two others. The two moths have been cred- been the target of a biological control pro- which survival to adult averaged 85%). ited with reducing seed production by up to gramme for the last 20 years, and since Minimal adult feeding was recorded on a 87% at some sites and for a large amount of 1983 a suite of biocontrol agents has been few Acacia and Mimosa species, but the leaf drop and stem dieback. Neurostrota introduced against it. results of further screening of these and gunniella abundance has been correlated other related species indicated that intro- Mimosa pigra is native to Central and with reduced seed output and canopy duction of the beetle would not impact on South America, extending from Mexico to growth, and C. mimosa has been shown to non-target species in Australia. Oviposition northern Argentina, but it has become further reduce seed production and has even normally occurs in the soil, so oviposition widespread as a weed in Africa and Asia as caused plant death in localized areas. Sub- testing was considered not to be applicable. well as Australia. Although it occurs in sequent regeneration of grasses and sedges small patches of inconspicuous and beneath heavily attacked plants, in turn, With testing completed successfully, Mala- straggly plants in its home range, in Aus- means it is more difficult for mimosa seeds corhinus irregularis was introduced to tralia it grows to 6 m tall and forms impen- to germinate and grow. Furthermore, bio- Australia in 2000. It is now reported to have etrable thorny thickets, which compete logical control integrates well with alterna- established successfully and to be inflicting with pastures, hinder mustering and pre- tive management options. Damage from significant damage to mimosa at release vent access to water. It also poses a serious biocontrol agents is greater on plant re- sites. At one site, last year’s seedlings were conservation problem as it can completely growth following burning, crushing or almost totally stripped of leaves by the alter the natural grass and sedge floodplain spraying. adults. It is too early to be able to assess landscape, replacing it with dense mono- larval impact, and plots continued to be Despite these promising results, control specific stands, and it threatens tourist monitored, but the signs are that this agent was still not adequate, and biocontrol scien- income in areas such as Kakadu National will indeed complement existing biocontrol tists continued to search for agents to com- Park. The weed grows at an alarming rate. agents by further reducing mimosa regener- plement those already at work. The agents Infestations in a river system can double in ation. area in just over a year following good rain- that had established by 2000 fed and repro- fall, and a single plant can produce more duced on flowers (1 sp.), seeds (1 sp.) and The latest agent to be released, Macaria than 200,000 seeds per year. Seeds are dis- stems (2 sp.), with only the ineffective pallidata, was another promising candidate persed mostly by water: some germinate Chlamisus mimosae attacking the leaves. as its larvae feed voraciously on Mimosa soon after release, others in subsequent sea- The best-performing agents were having a pigra leaves. They feed on both young and sons. good impact on seed production of mature mature foliage, first stripping the top sur- plants, so interest was focused on species face of leaves. At high densities they can In its home range, M. pigra is attacked by that fed on other plant parts; in particular, completely strip foliage, thus reducing some 440 insect herbivores and a number those that fed on foliage and/or seedlings plant growth and seed production. Are we on your mailing list? BiocontrolNews and Information is always pleased to receive news of research, conferences, new products or patents, changes in personnel, collaborative agreements or any other information of interest to other readers. If your organization sends out press releases or newsletters, please let us have a copy. In addition, the editors welcome proposals for review topics. 82N BiocontrolNews and Information 2002 Vol. 23 No. 4 Although exposed when feeding, they rest The mimosa biocontrol programme is a safety and cost. Evaluating potential haz- on leaf tips during the day in positions that joint programme of the Northern Territory ards for application equipment and opera- imitate stems, and they tend not to leave Government (Department of Infrastructure, tors on land occupied by kudzu is difficult. their host plant unless forced to look for a Planning and Environment) and CSIRO, Also, repeated application over several new food source. They are abundant and supported by the Australia Government’s years is required to kill the large corms, damaging in M. pigra’s native range in Natural Heritage Trust and previously by which can weigh up to 75 kg. Use of expen- Mexico and museum records indicate they the Australian Centre for International sive herbicides against infestations on land are widespread across tropical America. Agricultural Research. The slow but sure of marginal economic value is generally not Only genetic material from Mexico was success of the programme against this dan- cost effective. Furthermore, application of tested for host specificity. Because of the gerous wetland weed proves the value of herbicides over large areas threatens con- wide geographic range and the possibility taking a collaborative, sustained approach tamination of ground water. While several of the existence of a species complex, only against intractable invasive weed problems. herbicides are effective against kudzu, application of the most effective in prox- this Mexican genotype was released into By: Tim Heard, imity to aquatic habitats is discouraged. Australia. CSIRO Entomology, Long Pocket Labs, In response to these obstacles, an integrated Adult female Macaria pallidata oviposit 120 Meiers Rd, Indooroopilly, approach including biological control is indiscriminately on most surfaces when Qld 4068, Australia being studied. Biological control is almost confined in a cage, so host specificity Email: [email protected] never implemented by itself in the USA, assessments focused on larval development Fax: +61 7 3214 2885 but instead is usually part of an integrated testing, which was carried out using 70 management programme that may include And: Quentin Paynter, plant species at CSIRO’s Long Pocket Lab- herbicides, mechanical removal, livestock CSIRO Entomology, PMB 44, oratories in Queensland. In Mexico, open grazing, and more responsible land stew- Winnellie, NT 0822, Australia. field tests on 28 plant species were also ardship. The goal of a biological control Email: [email protected] conducted near the CSIRO Mexican Field programme is balance between kudzu and Station in Veracruz to determine oviposi- ❑ its new habitat. Natural enemies are the tion acceptability and larval development means by which this goal may be achieved suitability under natural conditions. As is and these may be found either in the habitat common amongst moths, adult M. palli- Biocontrol to Combat Kudzu to which kudzu is native or in its new hab- data do not feed destructively but only on itat.