Can genomics clarify the origins of Boreioglycaspis melaleucae in California,USA?

The Australian psyllid Boreioglycaspis melaleucae is a biological control agent of Melaleuca quinquenervia in Florida (USA) but was observed attacking M. quinquenervia trees in southern California (USA). Genotyping revealed the California population matched three of eight Australian haplotypes and all three Florida haplotypes. It remains unclear if the California psyllid population arrived directly from Australia or via Florida.     

Biology, distribution and host-range of the sawfly,Lophyrotoma zonalis (Hym. pergidae), a potential biological control agent for the paperbark tree,Melaleuca quinquenervia

Since its introduction into southern Florida at the beginning of this century, the Australian paperbark tree,Melaleuca quinquenervia (Cav.) S. T. Blake, has become a major economic and environmental pest. A project to develop biological control agents for this tree in Australia began in 1986. Among a number of potential agents, a defoliating sawfly,Lophyrotoma zonalis (Rohwer) (Hymenoptera: Pergidae), was selected for further study. The larvae of this sawfly are conspicuous defoliators ofMelaleuca trees in northern Queensland. We collected these sawflies from Cairns to Mackay in northern Queensland, and they are also known from the Northern Territory and New Guinea. The life-cycle from egg to adult takes about 12 weeks. The egg, larval and pupal stages are parasitized by dipteran and hymenopteran parasites. We conducted 2234 larval no-choice feeding tests on 46 plant species from 20 families. Although feeding occurred on 35 of these plant species,M. quinquenervia and its close relative,M. leucadendra (L.) L., were preferred. In oviposition tests, larvae only emerged from egg cases laid onM. quinquenervia andM. leucadendra. Our extensive field surveys of nearly 70 tree species foundL. zonalis eggs and larvae only on several closely relatedMelaleuca species. The potential effectiveness of this sawfly as a biocontrol agent is discussed and estimated using the Goeden-Harris scoring system. Quarantine studies of this insect began in Florida in early 1994.     

Biocontrol without borders: the unintended spread of introduced weed biological control agents

An underlying assumption of classical biological control implies that intentionally introduced natural enemies will remain within the boundaries that delineate the program’s area of implementation. A weed biological control program targeting Melaleuca quinquenervia in Florida, USA has resulted in the release and establishment of Oxyops vitiosa and Boreioglycaspis melaleucae. An international survey of M. quinquenervia populations in 13 other states or countries where the insects have not been intentionally introduced was initiated to monitor the long range dispersal of O. vitiosa and B. melaleucae beyond the herbivores’ intended geographic range (Florida). Surveys in 2006 resulted in the discovery of B. melaleucae within the canopies of several M. quinquenervia trees near San Juan, Puerto Rico. In 2007, O. vitiosa was observed on the island of New Providence in the Bahamas but neither herbivore was detected on nearby Grand Bahama or Andros islands. In 2009, B. melaleucae was observed attacking M. quinquenervia trees in Los Angeles, California (USA). The herbivores have not been detected on other surveyed M. quinquenervia populations in Cuba, Jamaica, Texas (USA), Costa Rica, Brazil, Hawaii (USA) or South Africa. There is no evidence to suggest that herbivore colonization of New Providence, Puerto Rico, or California was influenced by linear distance between Florida and the recipient M. quinquenervia stand. While the dispersal pathway(s) remains unknown, biological control agents were detected from 200 to >3500 km from their original release location (Florida) and at locations that have strong links via tourism and trade as indicated by the number of airline flights connecting south Florida with colonized tree populations. Implications of this unintended spread are discussed in relation to permeability of biogeographical barriers and risk assessment of biological control agents.     

Field colonization, population growth, and dispersal of Boreioglycaspis melaleucae Moore, a biological control agent of the invasive tree Melaleuca quinquenervia (Cav.) Blake

Invasion of native plant communities by the Australian paperbark tree (“melaleuca”), Melaleuca quinquenervia, complicates restoration of the Florida Everglades. Biological control, within the context of a comprehensive management program, offers a means to suppress regeneration of melaleuca after removal of existing trees and a mechanism to forestall reinvasion. To meet this need, a biological control program commenced in 1997 upon the release of an Australian weevil (Oxyops vitiosa [Pascoe] [Coleoptera: Curculionidae]). Release of a second biological control agent, the melaleuca psyllid (Boreioglycaspis melaleucae Moore), followed in February 2002 at field sites containing mixed age-class melaleuca stands or coppicing stumps. Each site was inoculated with 7000–10,000 adult psyllids, with one exception where 2000 nymphs were released on seedlings the following December. Psyllid populations established everywhere irrespective of colony source, site conditions, or the quantity released, although numbers released and, to a lesser degree, colony age influenced the numbers of colonies produced. Quantity included in the release was the major determinant of the resultant number of colonies, although the duration of their tenure in quarantine culture may have also influenced this. One site, comprised mainly of coppicing stumps, contained 3.3 million psyllids per ha within 3 months after release. Less than 1% of the coppices at a similar site harbored psyllid colonies 2 months after release (May 2002), but this rose to 75% in October then to 100% by December. The census population exceeded 715,000 adults and nearly 11 million nymphs by late January 2003. Psyllid populations dispersed 2.2–10.0 km/year, with the slower rates in dense, continuous melaleuca stands and faster rates in fragmented stands. Over 1 million psyllids had been redistributed to 100 locations as of December 2005. This species now occurs throughout much of the range of melaleuca in south Florida due to natural range expansion as well as anthropogenic dissemination.     

Nonselective oviposition by a fastidious insect: the laboratory host range of the melaleuca gall midge Lophodiplosis trifida (Diptera: Cecidomyiidae)

Invasion by the Australian paperbark, Melaleuca quinquenervia, has degraded large areas of south Florida wetlands. Restoration of these wetlands requires the removal of expansive monocultures of this large tree while simultaneously curtailing its spread. Management strategies developed by federal and state agencies include biological control to halt the spread of this species and to prevent reinfestation of cleared areas. This requires biological agents able to reduce flowering, seed production, and growth while increasing mortality of seedlings and saplings. Two of the three introduced agents (Oxyops vitiosa Pascoe and Boreioglycaspis melaleucae Moore) partially meet these needs but outcomes are not spatially or temporally consistent. Thus, additional agents are needed. The bud-gall fly Fergusonina turneri Taylor, with its mutualistic nematode Fergusobia quinquenerviae Davies and Giblin-Davis, is actively being released but has not established. A fourth promising agent, the gall midge Lophodiplosis trifida Gagné, manifested an extremely narrow host range during laboratory testing. Oviposition was indiscriminant in caged environments. Small, incipient, unilocular galls were initiated on Melaleuca viminalis, but larval development ensued only on M. quinquenervia. The unilocular galls on M. viminalis did not grow and produced no adult flies. As a result, M. viminalis test plants suffered only minor cosmetic damage. Observations from both Australia and Florida attest to the ability of this midge to impede M. quinquenervia growth and kill small plants. Thus, L. trifida is safe to release and will likely contribute to management objectives for control of this pernicious wetland invader.     

The molecular basis of host plant selection in Melaleuca quinquenervia by a successful biological control agent

Melaleuca quinquenervia (Cav) S.T. Blake (broadleaf paperbark) is an Australian tree that has become a serious weed in many places around the world. Two insects Oxyops vitiosa (the melaleuca weevil), and Boreioglycaspis melaleucae (the melaleuca psyllid), which were introduced to Florida as part of a biological control programme, have been very effective in reducing survival and reproduction of this weed. There are two terpene chemotypes of M. quinquenervia; one rich in the sesquiterpene E-nerolidol whereas the other is rich in viridiflorol. Viridiflorol is a strong feeding deterrent for the melaleuca weevil and retards larval development. The larvae therefore avoid the viridiflorol-rich chemotype, in contrast, female melaleuca psyllids prefer to oviposit on these leaves. To identify the molecular basis of these preferences, we isolated and characterised two terpene synthases from the viridiflorol-rich chemotype, both of which utilise farnesyl pyrophosphate and have the same product profile. Chemotypic variation in terpenes in M. quinquenervia is under strong genetic control and the reproductive potential of each chemotype is limited by a different insect. These insects could, therefore, be selective agents for the maintenance of chemotypic variation in M. quinquenervia.     

The genetic consequences of a demographic bottleneck in an introduced biological control insect

Population bottlenecks may result in the loss of genetic diversity, with potentially negative consequences for species of interest in conservation biology, including rare species, invasive species and biological control agents. We examined mtDNA sequence data and four variable microsatellite loci (SSRs) in the melaleuca psyllid Boreioglycaspis melaleucae, which was introduced from Australia to Florida as a biological control agent of the invasive plant Melaleuca quinquenervia. We sampled psyllids in the native and introduced ranges as well as individuals stored from the original founding population. There was a clear loss of mtDNA haplotype diversity, as well as a loss of rare microsatellite alleles, in the introduced range. However, there was little genetic differentiation between the home and introduced ranges, and no evidence for a genetic bottleneck based on an analysis of heterozygosity with the microsatellite markers. Overall, the data showed that the demographic bottleneck had a limited effect on the genetics of populations in the new range.     

Quarantine host range studies with Lophyrotoma zonalis, an Australian sawfly of interest for biological control of melaleuca, Melaleuca quinquenervia, in Florida, U.S.A.

The Australian melaleuca tree, Melaleuca quinquenervia (Cav.) S. T. Blake (Myrtaceae), has naturalized in southern Florida,U.S.A., and is now one of that regions most important weeds.Primarily a weed of wetlands, it also infests neighboring drierareas. Current efforts to restore the South Florida ecosystem arethreatened by the continuing range expansion of melaleuca andother weeds. In an effort to supplement the current chemical andcultural control methods for melaleuca, a search for potentialbiological control agents was begun in Australia in 1986. Thesawfly, Lophyrotoma zonalis, was determined after extensive fieldand laboratory studies to have potential as a biological controlagent. Larvae of L. zonalis eat leaves and occasionally defoliatelarge trees in Australia. Host range studies were conducted in aFlorida quarantine facility with native and cultivated plantspecies. Multi-choice and no-choice oviposition tests wereconducted with 36 species in the Myrtaceae and with 18 species inother families. Larvae developed to prepupae and adults from theeggs oviposited on 23 species of Myrtaceae only on 3 species ofbottlebrushes, Callistemon. Medium-sized larvae were tested forfeeding on bouquets of plant cuttings and on potted plants. Theyare the stage that might wander from defoliated trees. Noticeablefeeding, but much less than on melaleuca, was restricted to theMyrtaceae, except for a few individual larvae that fed on waxmyrtle, Myrica cerifera. Medium-sized larvae became prepupae onlyon Melaleuca decora (73%) and on wax myrtle (10%). However,neither species received eggs in the oviposition tests. Thesestudies confirmed the narrow host range of L. zonalis aspreviously reported from field and laboratory studies inAustralia.     

Concordance between life history traits, invasion history, and allozyme diversity of the Everglades invader Melaleuca quinquenervia

During the century following its initial introduction in 1886, the Australian tree Melaleuca quinquenervia (Myrtaceae) dispersed from a few introduction points to occupy over 200,000 ha, primarily in historic Everglades wetlands of southern Florida. Cellulose acetate gel electrophoresis (CAGE) was used to investigate the allozyme diversity and population genetic structure of 208 individuals in a dozen populations resulting from this invasion. The analyses showed that these populations have a high (82%) rate of polymorphic loci and an average of 2 alleles/locus. There was substantial heterozygosity (mean H_e = 0.356), which concords well with recent studies reporting a greater number of introduction events and sources than generally recognized. The introduction history and distributional patterns within Florida have led to geographic structuring (G_ST = 0.419) in which the Gulf Coast metapopulation has a greater effective number of alleles and greater heterozygosity than the Atlantic Coast metapopulation. The gene diversity in M. quinquenervia was comparable to other tropical woody species. Its strong population divergence was reminiscent of pioneer species and consistent with its status as a plant invader in Florida.     

Field colonization,population growth,and dispersal of Boreioglycaspis melaleucae Moore,a biological control agent of the invasive tree Melaleuca quinquenervia (Cav.) Blake

Invasion of native plant communities by the Australian paperbark tree (“melaleuca”), Melaleuca quinquenervia, complicates restoration of the Florida Everglades. Biological control, within the context of a comprehensive management program, offers a means to suppress regeneration of melaleuca after removal of existing trees and a mechanism to forestall reinvasion. To meet this need, a biological control program commenced in 1997 upon the release of an Australian weevil (Oxyops vitiosa [Pascoe] [Coleoptera: Curculionidae]). Release of a second biological control agent, the melaleuca psyllid (Boreioglycaspis melaleucae Moore), followed in February 2002 at field sites containing mixed age-class melaleuca stands or coppicing stumps. Each site was inoculated with 7000–10,000 adult psyllids, with one exception where 2000 nymphs were released on seedlings the following December. Psyllid populations established everywhere irrespective of colony source, site conditions, or the quantity released, although numbers released and, to a lesser degree, colony age influenced the numbers of colonies produced. Quantity included in the release was the major determinant of the resultant number of colonies, although the duration of their tenure in quarantine culture may have also influenced this. One site, comprised mainly of coppicing stumps, contained 3.3 million psyllids per ha within 3 months after release. Less than 1% of the coppices at a similar site harbored psyllid colonies 2 months after release (May 2002), but this rose to 75% in October then to 100% by December. The census population exceeded 715,000 adults and nearly 11 million nymphs by late January 2003. Psyllid populations dispersed 2.2–10.0 km/year, with the slower rates in dense, continuous melaleuca stands and faster rates in fragmented stands. Over 1 million psyllids had been redistributed to 100 locations as of December 2005. This species now occurs throughout much of the range of melaleuca in south Florida due to natural range expansion as well as anthropogenic dissemination.     

Ultrastructure of Wax-Producing Structures on the Integument of the Melaleuca Psyllid Boreioglycaspis melaleucae (Hemiptera: Psyllidae), with Honeydew Excretion Behavior in Males and Females

The melaleuca psyllid, Boreioglycaspis melaleucae (Hemiptera: Psyllidae), was introduced to Florida as a biological control agent against Melaleuca quinquenervia, an invasive evergreen tree that has invaded large areas of Florida Everglades. Colonies of B. melaleucae nymphs are normally covered by white waxy secretions, and nymphs of various instars produce long bundles of white waxy filaments extending laterally and posteriorly from their abdomen. Scanning electron microscopy of ‘naturally waxed’ and ‘dewaxed’ nymphs (cleaned from wax) revealed two types of wax pore plates located dorsally and laterally on the integument of posterior abdominal segments starting with the 4th segment. Type-1 wax pore plates, with raised rim, peripheral groove, slits and pits, produce long ribbons and filaments of waxy secretions that are wound together forming long wax bundles, whereas type-2 wax pore plates, with slits only, produce shorter wax curls. Additionally, in both nymphs and adult females, the circumanal ring contained ornate rows of wax pores that produce wax filaments covering their honeydew excretions. Video recordings with stereomicroscopy showed that adult females produce whitish honeydew balls, powerfully propelled away from their body, probably to get these sticky excretions away from their eggs and newly hatched nymphs. Adult males, however, produce clear droplets of honeydew immediately behind them, simply by bending the posterior end of the abdomen downward. The possible role(s) of waxy secretions by nymphs and adults of B. melaleucae in reducing contamination of their colonies with honeydew, among other possibilities, are discussed.     

An evaluation of the impact of Melaleuca quinquenervia invasion and management on plant community structure after fire

Two questions were asked in this study: after a fire, does the choice of invasive plant management strategy, namely herbicidal or biological, alter (1) plant community assemblages and (2) the re-invasion potential of the Australian tree Melaleuca quinquenervia? Plant species richness was highest in the non-invaded and herbicide sites compared to the biological site with 10.5, 10.8, and 8.25 species m⁻² found in each site, respectively. Although the total count of live and dead seedlings was highest in the biologically controlled site at 22.8 and 13.6 plants m⁻², respectively, M. quinquenervia seedlings were recruited in all sites. While the ultimate goal of management programs is to restore ecosystem integrity, this work provides evidence that passive restoration may not be enough to restore plant community structure in this system.     

Root development and competitive ability of the invasive species Melaleuca quinquenervia (Cav.) S.T. Blake in the South Florida flatwoods

Melaleuca quinquenervia (Cav.) S.T. Blake is an aggressive, invasive species in sub-tropical Florida that is considered a serious threat to the existing biological integrity of many subtropical ecosystems in south Florida. It prevents other species from thriving through its high rate of seed production/germination and the formation of a dense tree canopy. However, its ability to take over a site between initial seedling establishment and crown closure is not well understood. The objective of this study was to determine (i) the nature of root development with time and soil depth, and (ii) the ability of M. quinquenervia to invade and absorb nutrients from soil already occupied by native vegetation. The working hypotheses were that M. quinquenervia captures a site either by (i) tolerating competition by prolifically growing roots into soil already occupied by native plants, or (ii) avoiding competition by rooting to depths where inter-root competition is less and water supply during a drought is available. Soil trenches and in-growth trays were used to measure root distribution and growth. Root number (# m^–2), root length density (m root m^–3 soil volume), and root biomass (g root m^–3 soil) were determined. This study demonstrated that M. quinquenervia (1) is a prolific rooter with or without the presence of competing vegetation; (2) can develop root densities higher than many mature native species at an early age; (3) can develop roots in the soil surface during soil drying periods, even while competitive grasses are dying out; (4) can develop a deep root system at an early age; and (5) is an effective rooter in both moist and dry water regimes in this fluctuating water table soil. The data suggested that this species is a strong competitor through the use of both competition avoidance and tolerance mechanisms and that the rooting habit of M. quinquenervia should be an important consideration when evaluating its ability as an invasive species.     

Initial impacts and field validation of host range for Boreioglycaspis melaleucae Moore (Hemiptera: Psyllidae), a biological control agent of the invasive tree Melaleuca quinquenervia (Cav.) Blake (Myrtales: Myrtaceae: Leptospermoideae)

Invasion of south Florida wetlands by the Australian paperbark tree, Melaleuca quinquenervia (Cav.) S.T. Blake (melaleuca), has caused adverse economic and environmental impacts. The tree's biological attributes and favorable ambient biophysical conditions combine to complicate efforts to restore and maintain south Florida ecosystems. Management requires an integrated strategy that deploys multiple biological control agents to forestall reinvasion and to supplement other control methods, thereby lessening recruitment and regeneration after removal of existing trees. This biological control program began during 1997 when an Australian weevil, Oxyops vitiosa (Pascoe), was released. A second Australian insect, the melaleuca psyllid (Boreioglycaspis melaleucae Moore), first introduced during 2002, has also widely established. After inoculation of the psyllid in a field study, only 40% of seedlings survived herbivory treatments compared with 95% survival in controls. The resultant defoliation also reduced growth of the surviving seedlings. A weevil-induced decline at a site comprised mainly of coppicing stumps had slowed after a 70% reduction. Psyllids colonized the site, and 37% of the remaining coppices succumbed within 10 mo. The realized ecological host range of B. melaleucae was restricted to M. quinquenervia; 18 other nontarget plant species predicted to be suboptimal or nonhosts during laboratory host range testing were unaffected when interspersed with psyllid-infested melaleuca trees in a common garden study. Evaluations are ongoing, but B. melaleucae is clearly reducing seedling recruitment and stump regrowth without adversely impacting other plant species. Manifestation of impacts on mature trees will require more time, but initial indications suggest that the psyllid will be an effective supplement to the weevil.     

Decline in exotic tree density facilitates increased plant diversity: the experience from Melaleuca quinquenervia invaded wetlands

The Australian tree Melaleuca quinquenervia (melaleuca) formed dense monocultural forests several decades after invading parts of Florida and the Caribbean islands. These dominant forests have displaced native vegetation in sensitive wetland systems. We hypothesized that native plant diversity would increase following recent reductions in density of mature melaleuca stands in south Florida. We therefore examined data on changes in melaleuca densities and plant species diversity derived from permanent plots that were monitored from 1997 to 2005. These plots were located within mature melaleuca stands in nonflooded and seasonally-flooded habitats. Two host-specific biological control agents of melaleuca, Oxyops vitiosa and Boreioglycaspis melaleucae, were introduced during 1997 and 2002, respectively. Also, an adventive rust fungus Puccinia psidii and lobate-lac scale Paratachardina pesudolobata became abundant during the latter part of the study period. Overall melaleuca density declines in current study coincided with two to four fold increases in plant species diversity. The greatest declines in melaleuca density as well as the greatest increases in family importance values and species diversity indices occurred in nonflooded as compared to seasonally-flooded habitats. Most pioneer plant species in study sites belonged to Asteraceae, Cyperaceae, Poaceae, and Ulmaceae. The rapid reduction in melaleuca density and canopy cover during the study period may be attributed to self-thinning accelerated by the negative impact of natural enemies. Densities of other woody plants, particularly Myrica and Myrsine, which were sparsely represented in the understory by a few suppressed individuals also declined during the same period, possibly due to infestation by the generalist lac-scale. These findings indicate that natural-enemy accelerated self-thinning of melaleuca densities is positively influencing the native plant diversity and facilitating the partial rehabilitation of degraded habitats.     

New lichenicolous, muscicolous, corticolous and lignicolous taxa of Burgoa s. l. and Marchandiomyces s. l. (anamorphic Basidiomycota), a new genus for Omphalinafoliacea, and a catalogue and a key to the non-lichenized, bulbilliferous basidiomycetes

A catalogue and a key to the non-lichenized, bulbilliferous basidiomycetes are given. The new genus Burgella is described for the lichenicolous B. flavoparmeliae, phylogenetically close to Sistotrema oblongisporum and Multiclavula. The genera Pneumatospora and Tricellulortus are placed in synonymy of Minimedusa, the new combination M. obcoronata is proposed, and the new facultative lichenicolous M. pubescens is described. The new facultative lichenicolous Burgoa angulosa is phylogenetically close to the generic type B. verzuoliana, whilst the new B. moriformis and B. splendens are provisionally included in the genus Burgoa. A Burgoa-like species in the Ceratobasidiaceae is left unnamed. Two new species of Marchandiomyces, M. buckii and M. nothofagicola, are described. As Marchandiomyces aurantiacus is phylogenetically more close to Erythricium than to Marchandiomyces, it is proposed to exclude it from that genus and to use the holomorphic generic name Marchandiobasidium for both anamorph and teleomorph of this species. The new genus Marchandiomphalina is introduced for the lichenized Omphalina foliacea, a taxon phylogenetically close to Marchandiobasidium. Taxonomic novelties Burgella Diederich & Lawrey; B. flavoparmeliae Diederich & Lawrey; Burgoa angulosa Diederich, Lawrey & Etayo; B. moriformis Diederich, Ertz & Coppins; B. splendens Diederich & Coppins; Marchandiomphalina Diederich, Lawrey & Binder; Marchandiomphalina foliacea (P. M. J?rg.) Diederich, Lawrey & Binder; Marchandiomyces buckii Diederich & Lawrey; M. nothofagicola Diederich & Lawrey; Minimedusa pubescens Diederich, Lawrey & Heylen; M. obcoronata (B. Sutton, Kuthub. & Muid) Diederich & Lawrey     

Physiological host range of two highly specialised mutualistic symbiotes: the fly Fergusonina turneri and its obligate nematode Fergusobia quinquenerviae,potential biocontrol agents of Melaleuca quinquenervia

In Australia, galls develop on Melaleuca quinquenervia (Cav.) S.T. Blake (Myrtaceae) as a result of the mutualistic association between the fly Fergusonina turneri Taylor (Diptera: Fergusoninidae) and its obligate nematode Fergusobia quinquenerviae Davies & Giblin-Davis (Tylenchida: Sphaerulariidae). The nematode induces gall formation, whereas the fly promotes gall maturation. Together they exploit M. quinquenervia buds and may inhibit stem elongation and flower formation. We delimited the physiological host range of this pair to determine their suitability as biological control agents of invasive M. quinquenervia populations in Florida, USA. Host use was assessed for eight species of Myrtaceae native to Florida, eight phylogenetically related ornamental species and oviposition alone on five non-myrtaceous species. Although oviposition was less specific, galls developed and matured only on M. quinquenervia. After establishment, galls are predicted to prevent flower and seed production, thereby reducing the regenerative potential of M. quinquenervia. This is the first example of an insect/nematode mutualism released as biological control agents of an invasive plant.     

Alcidodes sedi (Col.: Curculionidae), a natural enemy of Bryophyllum delagoense (Crassulaceae) in South Africa and a possible candidate agent for the biological control of this weed in Australia

The Madagascan endemic, Bryophyllum delagoense (Crassulaceae), is a major weed in Queensland, Australia. Despite having first been recorded in Australia in the 1940s, it is far more invasive there than on the African mainland where it was introduced more than 170 years ago. This may be due to a number of factors, one of which could be the occurrence of new natural enemy associations in southern Africa. Among the insects of crassulaceous plants that have extended their host ranges, a stem-boring weevil, Alcidodes sedi, was studied to elucidate its status as a natural enemy of B. delagoense in southern Africa and as a candidate biological control agent for introduction to Australia. Laboratory studies indicated that damage inflicted by adult and larval feeding caused significant reductions in stem length and number of leaves. Preliminary host-range trials revealed that A. sedi can complete its development on other species in the Crassulaceae, including most of the introduced Bryophyllum species and some Kalanchoe species native to South Africa. Despite the oligophagous nature of A. sedi and the fact that it can complete its development on a number of ornamental species in the Crassulaceae, it should be considered a potential biological control agent in Australia. All of the native Crassulaceae in Australia are in the genus Crassula, most of which are very small and therefore unlikely to support the development of a large weevil like A. sedi. However, additional host-range trials will have to be undertaken in Australia to determine whether the weevil can be considered safe for release.     

Maintenance of a narrow host range by Oxyops vitiosa; a biological control agent of Melaleuca quinquenervia

Host range expansion in insect herbivores is often thought to be mediated by several factors, principal among them are secondary plant metabolites. In weed biological control, the host range of a prospective agent is one of the most important considerations in its implementation. Extensive host testing tests seek to determine the behavioral acceptance and nutritional value of different test plant species to the potential agent. A list of test plants is compiled that comprises species that are close taxonomic relatives of the target weed plus other species of economic or ecologic importance. The host testing of the Melaleuca quinquenervia biological control agent Oxyops vitiosa indicated that larvae would accept and complete development on the Australian target weed M. quinquenervia, two Australian ornamental species, Callistemon citrina, Callistemon viminalis (all Myrtaceae). However, the larvae did not complete development when fed a North American species Myrica cerifera (Myricaceae). The study reported here confirms these results and examines the nutritional and performance differences in O. vitiosa larvae fed leaves of these species. The leaf quality factors, percent moisture, percent nitrogen, toughness, and terpenoid content were related to larval survival, performance and digestive indices. The results indicate that plant quality among the Myrtaceae species was generally similar and correspondingly larval survival, performance and digestive indices differed little when larvae were fed leaves of these species. However, significant differences occurred in the plant quality of the North American M. cerifera compared with the Australian species which had leaves with the lowest percent moisture, lowest leaf toughness, highest percent nitrogen. This species, however, is not a physiological host as none of the neonates survived to pupate. When third instars were switched to M. cerifera from their normal host M. quinquenervia reductions were found in survival, biomass gain, digestive efficiency, and conversion of digested food to insect biomass. The marginal acceptance of this North American native plant in laboratory bioassays appears related to the terpenoid chemistry that has similarities to the taxonomically unrelated host M. quinquenervia. However, the high larval mortality corresponds to several novel terpenoids that are not present in the host. For weed biological control host testing these results indicate that M. cerifera is a poor host for O. vitiosa. Additionally, future test plant lists should include plants with secondary metabolites similar to the target weed as these compounds may constitute behavioral cues that are relevant to these specialized herbivores.     

中国新入侵害虫——桉梳木虱(半翅目:木虱科)

2018年5月,在云南省昆明市金殿森林公园种植的蓝桉树苗上采集到了一种密集发生的木虱,其成虫和若虫均严重危害桉树叶片。经鉴定为桉梳木虱,该种木虱原产于澳大利亚,此前已入侵欧洲、非洲、北美洲、南美洲和亚洲的一些国家,危害桉树。本文提供了桉梳木虱的危害情况和形态鉴别特征,提出了防范扩散危害的措施建议。