Target For Biological Control Research Articles

Progress and Prospects for the Biological Control of Invasive Alien Grasses Poaceae) in South Africa

Historically, invasive alien grasses have not been considered a major threat in South Africa, and as a result, very few resources are allocated to their management. However, there is an increasing awareness of the severe environmental and socio-economic impacts of invasive grasses and the need for appropriate management options for their control. South Africa has a long history of successfully implementing weed biological control (biocontrol) to manage invasive alien plants, however much like the rest of the world, invasive grasses do not feature prominently as targets for biocontrol. The implementation and early indicators of success of the few grass biocontrol programmes globally and the finding that grasses can be suitable targets, suggests that biocontrol could start to play an important role in managing invasive alien grasses in South Africa. In this paper, we evaluated the prospects for implementing novel grass biocontrol projects over the next ten years against 48 grasses that have been determined to represent the highest risk based on their current environmental and economic impacts. The grasses were ranked in order of priority using the Biological Control Target Selection system. Five grasses were prioritised – Arundo donax L., Cortaderia jubata (Lem.) Stapf, Cortaderia selloana (Schult & Schult) Asch. & Graebn., Nassella trichotoma (Hack. ex Arech.), and Glyceria maxima (Hartm.) Holmb., based on attributes that make them suitable biocontrol targets. Arundo donax has already been the target of a biocontrol programme in South Africa. We reviewed the progress made towards the biocontrol of this species and discuss how this programme could be developed going forward. Moreover, we outline how biocontrol could be implemented to manage the remaining four high-priority targets. While biocontrol of grasses is not without its challenges (e.g. unresolved taxonomies, conflicts of interest and a lack of supporting legislation), South Africa has an opportunity to learn from existing global research and begin to invest in biocontrol of high-priority species that are in most need of control.

Uncovering the phylogeography of Schinus terebinthifolia in South Africa to guide biological control.

Schinus terebinthifolia is a problematic invasive alien plant (IAP) in South Africa that is a high priority target for biological control. Biological control has been implemented in the states of Florida and Hawaii (USA), where S. terebinthifolia is also an IAP. Phylogeographic work determined that there have been multiple introductions of two lineages (haplotype A and B) into the USA. Haplotype A was introduced to western Florida and Hawaii, while haplotype B was introduced to eastern Florida. Haplotypes A and B have subsequently hybridized in Florida, resulting in novel plant genotypes. Biological control agents in the USA are known to vary in efficacies on the two different haplotypes and hybrids. This study used molecular techniques to uncover the source populations of S. terebinthifolia in South Africa using chloroplast DNA and microsatellites. Populations from the introduced ranges in Florida (east, west and hybrids) and Hawaii were included (n = 95). All South Africa populations (n = 51) were found to be haplotype A. Microsatellite analysis determined shared alleles with western Florida and Hawaiian populations. The likely source of South African S. terebinthifolia was determined to be western Florida through the horticultural trade. These results will help guide a biological control programme to source agents that perform well on these populations in the USA. Furthermore, the presence of only one haplotype in South Africa highlights the need to ensure no further introductions of other haplotypes of the plant are made, in order to avoid similar hybridization events like those recorded in Florida.

Variations in chemical defences and patterns of natural enemy attack between native and introduced populations of fireweed (Senecio madagascariensis): Implications for biological control

AbstractNative to South Africa, fireweed (Senecio madagascariensis Poiret; Asteraceae) is an annual or short‐lived perennial herb that is highly invasive in Australia, where it is a target for biological control. Preliminary research indicates that fireweed may be undergoing adaptive changes along its invasion gradient in Australia. Changes, such as a shift in plant chemical defence, may influence fireweed’s interaction with specialist insect herbivores, and hence the efficacy of a biocontrol program. As the testing of biocontrol candidates is a rigorous and lengthy process, confirmation of fireweed’s susceptibility to insect attack may assist in fast tracking candidate suitability, where changes in plant defensive chemistry are found. In a large experimental field study in fireweed’s native range, we compared the susceptibility of Australian and South African populations to insect natural enemy attack (in terms of plant biomass, insect richness and composition). Simultaneously, we assessed the variation in plant pyrrolizidine alkaloid concentrations and composition to rationalise any differences in natural enemy attack between populations. We found no significant differences in plant biomass across fireweed populations, despite significantly higher alkaloid concentrations in Australian populations. The composition of the endophagous (specialist) insect herbivore assemblage was related to alkaloid composition, but there were only minor differences in the assemblage between Australian and South African fireweed populations. Moreover, we found no significant differences in the abundance, richness or Shannon diversity indices of endophagous or ectophagous (generalist) insect herbivores between Australian and South African fireweed populations. Our results suggest that despite variations in chemical defence, Australian fireweed populations displayed neither reduced nor increased susceptibility to specialist insect herbivore attack, supporting the notion that if host‐specific biocontrol agents are released, their impact in Australia is unlikely to be influenced by any changes in plant chemical defence.

Seasonal abundance and host-plant affinities of Longitarsus basutoensis and related flea beetles associated with the invasive Senecio madagascariensis in their native range in KwaZulu-Natal, South Africa

Senecio madagascariensis Poiret (Asteraceae) is a target for biological control in Australia and Hawaii, with several candidate insect agents recorded in KwaZulu-Natal, South Africa, the confirmed origin of the invasive populations. Although the root-feeding Longitarsus basutoensis Bechyné (Chrysomelidae: Galerucinae: Alticini) was prioritised for assessment, similar flea beetle taxa were also considered. We first investigated the seasonal abundance of L. basutoensis and related taxa on S. madagascariensis populations in the KwaZulu-Natal Midlands. Second, we assessed their host-plant affinities by surveying 17 non-target native Senecio species in the region. We used DNA CO1 barcoding to differentiate flea beetle taxa and their root-feeding larvae in both studies. Monthly sampling revealed three root-feeding taxa associated with S. madagascariensis, with L. basutoensis the most abundant. Longitarsus basutoensis was recorded throughout the year, with no clear patterns in seasonal abundance but significantly higher numbers at sites with deep, well drained soils that have high water holding capacity. Two unidentified flea beetle taxa, represented by larval specimens only, were recorded infrequently and in low numbers. The host-range study revealed 18 flea beetle taxa on 11 Senecio species, with L. basutoensis the most abundant species and recorded mostly on S. madagascariensis. Longitarsus basutoensis was also detected on four non-target Senecio species which, together with the results of preliminary host-specificity tests, indicated insufficient host-range restriction for countries like Australia that host a diverse Senecio flora. However, L basutoensis may have potential for release in Hawaii, due to a lack of native Senecio species on any of its islands.

Establishment of the biological control agent Hypocosmiapyrochroma for Dolichandraunguis‐cati (Bignoniaceae) is limited by microclimate

AbstractCat's claw creeper, Dolichandra unguis‐cati (Bignoniaceae), a perennial woody vine native to tropical America, is a target for biological control in Australia and South Africa. The cat's claw creeper leaf‐tying moth Hypocosmia pyrochroma (Lepidoptera: Pyralidae) from tropical South America was released as a biological control agent for cat's claw creeper in Australia from 2007 to 2010. A total of 2,277 adults, 837 pupae and 77,250 larvae were released at 40 sites in Queensland and New South Wales. Releases were made mostly in open fields (85%), and at limited sites (15%) in insect‐proof cages erected over naturally occurring cat's claw creeper infestations in the field. Sampling was conducted annually in spring and autumn to monitor the establishment and dispersal of H. pyrochroma. Establishment of H. pyrochroma was first noticed in 2012 at three release sites and since then the number of established sites has increased to 80 in 2020. Establishment was evident on both ‘short‐pod’ and ‘long‐pod’ forms of cat's claw creeper and was more widespread in sites where releases were made within insect‐proof field cages (50%) than in sites with open field releases (9%). The moth was active from late spring to late autumn with peak larval activity in late summer. To date, all field establishments have been in areas predicted by a CLIMEX model as climatically suitable but restricted mostly to riparian environment (93% of establishment), where the moth has continued to spread from 1.5 to 23 km from release sites. In contrast, there is the only limited establishment and spread in non‐riparian corridors, highlighting the role of microclimate (riparian) as a limiting factor for establishment and spread. Future efforts will focus on redistribution of the agent to river/creek systems where the moth is currently not present.

Prioritisation of targets for weed biological control III: a tool to identify the next targets for biological control in South Africa and set priorities for resource allocation

ABSTRACT Biological control is an effective and sustainable method for management of invasive alien plants (IAPs), and has been implemented on 68 of the 367 plant species that are listed as legally requiring management strategies under South Africa’s National Environmental Management: Biodiversity Act (10/2004): Alien and Invasive Species Regulations. With limited resources and funding available, it can realistically only be considered for a subset of the remaining alien plants for which biocontrol has not yet been implemented. Considerable funding has been allocated towards biocontrol in South African in the past, principally through the Working for Water Programme of the Nature Resource Management Programmes (Department of Environment, Forestry and Fisheries), and this support is expected to continue with the intention of increasing the number of IAPs under this management approach in the future. To ensure appropriate targets are selected, the Biological Control Target Selection (BCTS) system was applied to the alien plants on this list that are not under biocontrol (299 species). This paper presents the resultant list of top priority species that represent good investments for biocontrol when funds are available.

Prioritisation of targets for weed biological control II: the South African Biological Control Target Selection system

ABSTRACT Invasive alien plants (IAPs) are considered one of the greatest threats to biodiversity in South Africa and are often associated with negative socio-economic and human health consequences. Biocontrol is seen as an effective strategy for managing IAPs however it can realistically only be considered for a subset of such plants given the limited funding resources available. Some plants are also better targets for biocontrol than others. This paper develops a prioritisation system to create an objective, transparent and easily usable method in which to target IAPs plants that are most suited to biocontrol in South Africa. The Biological Control Target Selection (BCTS) system builds on twelve previously developed prioritisation systems. The system uses three sections encompassing thirteen attributes that are combined to present the highest predicative powers to rank potential target IAPs as biocontrol targets.

Biology and native host range of the defoliating beetle Ageniosa cf. badenii (Chrysomelidae), a potential biological control agent for Cape ivy (Delairea odorata) in invaded countries

ABSTRACT Delairea odorata Lemaire, Cape ivy (Asteraceae: Senecioneae), is native to South Africa but invasive in several countries. The plant is a target for biological control in the USA (California and Hawaii) and Australia, where its aggressive smothering tendencies threaten native ecosystems. The beetle Ageniosa cf. badenii (Vogel) (Chrysomelidae) was investigated in South Africa as a potential agent for D. odorata in invaded countries. Adults are wingless and nocturnal. Females deposit clusters of 1–10 eggs on the leaf undersides. Neonate larvae are highly mobile and feed on the leaves during the four instars, before pupating in the soil. Mean (± SE) developmental time from egg hatch to adult emergence was 30.8 ± 0.4 days on D. odorata. During larval no-choice tests with 34 asteraceous plant species, survival to adulthood was confined to 10 species in the tribe Senecioneae. Neonate larvae completed development (with sustained fitness ≥ 65% in relation to the highest ranked host) on three native (Senecio tamoides DC., D. odorata and S. skirrhodon DC.) and one exotic (Gynura procumbens (Lour.) Merr.) species. The beetle’s narrow host range was confirmed by larval paired-choice and adult multi-choice tests and field observations. Ageniosa cf. badenii may be a suitable agent for Hawaii, where the tribe Senecioneae is not represented in the native flora. However, since Senecioneae are well represented in the native flora of Australia and California, more intensive testing is needed to determine if the beetle is a candidate for introduction into these areas.

DNA barcoding of endophagous immature stages elucidates the host-plant affinities of insects associated with the invasive Senecio madagascariensis in its native range in South Africa

Senecio madagascariensis Poiret (Asteraceae), an invasive herb from southern Africa that inflicts high economic losses in several countries worldwide, is currently a target for biological control in Australia and Hawaii. Several candidate insect agents were identified from the weed’s native range in South Africa. Confirmation of narrow host ranges, prior to agent importations into quarantine, is important for Australia given its rich native Senecio flora. In particular, surveys for candidate agents on closely related non-target plants in the native range can differentiate between host specific and unsuitable agents at an early stage. This study focused on endophagous insects from families that were deployed in biocontrol programmes against other weedy Asteraceae. The host-plant affinities of stem-boring Coleoptera and stem-boring and capitulum-feeding Lepidoptera and Diptera were assessed across 18 native herbaceous Senecio species in KwaZulu-Natal, South Africa. Since larval morphology is typically unable to confirm insect identity, DNA barcoding was used to differentiate between insect species associated with different Senecio species to determine their host-plant affinities. COI phylogenies revealed that stem-boring Curculionidae and Tortricidae and capitulum-feeding Pterophoridae and Tephritidae that are associated with S. madagascariensis were restricted to plants in the S. madagascariensis species complex. In contrast, none of the stem-boring Agromyzidae were restricted to S.madagascariensis or its species complex. This study has supported the selection of several potentially host-specific agents for S. madagascariensis that could be imported for quarantine testing in Australia and Hawaii.

Host selection of Dolichogenidea tasmanica: implications for conservation biological control of light brown apple moth

ABSTRACTAn understanding of host selection by parasitoids can help in evaluating alternative host candidates to make conservation biological control of a target pest more reliable. This study investigated the host selection behaviour of Dolichogenidae tasmanica (Hymenoptera: Braconidae) in response to two related tortricid host species (Lepidoptera). The light brown apple moth, Epiphyas postvittana is the biological control target in Australian vineyards, while Merophyas divulsana was selected to evaluate its potential as an alternative host. We quantified the effects of host species, ages and experiences on the landing preferences of the parasitoid in dual choice tests. The effects of these host species on developmental time, sex ratio and body size of adult parasitoids were also examined. During all observations, D. tasmanica exhibited no statistically significant preferences in response to these hosts. Host species did not affect the body size of the wasp, but did influence its developmental time, possibly due to a trade-off between body size and developmental time of the wasp, which took longer in the smaller host, M. divulsana. The sex ratio was similar within host instars and between host species. These results suggest that M. divulsana should be a promising alternative host to support the local parasitoid population in vineyards as part of a conservation biological control programme that targets E. postvittana.

Insect herbivores associated with the invasive herb Senecio madagascariensis (Asteraceae) in its native range in KwaZulu-Natal, South Africa and their potential as biological control agents in invaded countries

ABSTRACTNative to southern Africa, Senecio madagascariensis Poir. (fireweed, Asteraceae) has invaded agricultural lands and disturbed areas in several countries worldwide and is currently a target for biological control in Australia and the USA (Hawaii). Quantitative surveys of the plant in KwaZulu-Natal, South Africa, considered the origin of the Australian and Hawaiian populations, revealed several insect herbivore taxa that are frequently associated with the plant’s foliar, floral and structural tissues. These largely comprised ectophagous sap suckers (34%), chewers (29%) and root feeders (1%), but also endophagous stem borers (21%), capitulum feeders (13%) and leaf miners (2%). Many of these taxa were encountered only occasionally or rarely during sampling, with some displaying low to very low abundance. Based on these surveys and earlier precedents in biocontrol programmes against other invasive Asteraceae, 15 taxa were shortlisted as candidate agents. Of these, four were prioritised for host-range assessments which are currently in progress. These include the capitulum-feeding Homoeosoma stenotea Hampson (Lepidoptera: Pyralidae), the stem-boring Gasteroclisus tricostalis (Thunberg) (Coleoptera: Curculionidae) and Metamesia elegans (Walsingham) (Lepidoptera: Tortricidae) and the root-feeding Longitarsus basutoensis Bechyné (Coleoptera: Chrysomelidae: Alticinae). Although the diversity of native Senecio species in Australia may present challenges during routine host-specificity testing, prospects for the biocontrol of S. madagascariensis in Hawaii appear very promising, since the native flora does not include any species in the tribe Senecioneae.

Implications of the changing phylogenetic relationships of Acacia s.l. on the biological control of Vachellia nilotica ssp. indica in Australia

Plant relationships have implications for many fields including weed biological control. The use of DNA sequencing and new tree building algorithms since the late 1980s and early 1990s have revolutionised plant classification and has resulted in many changes to previously accepted taxonomic relationships. It is critical that biological control researchers stay abreast of changes to plant phylogenies. One of the largest plant genera, Acacia, has undergone great change over the past 20 years and these changes have ramifications for weed biological control projects in a number of countries. Vachellia nilotica (prickly acacia) is a major weed in Australia, originating from the Indian subcontinent and Asia, and it has been a target for biological control since 1980. Once a member of Acacia, a large (>1,000 spp.) and iconic group in Australia, prickly acacia is now part of the genus Vachellia. Current knowledge suggests that Vachellia is more closely related to mimosoid genera than it is to Acacia s.s. There has also been a recent reclassification of legume subfamilies with subfamily Mimosoideae now part of subfamily Caesalpinioideae, and four new subfamilies. In this paper we review the changes that have occurred to this group since the prickly acacia biological control project began and discuss the implications for the project. A new host test list for quarantine testing is proposed. Developed following the modernisation of the centrifugal‐phylogenetic method, it is shorter than past lists, containing 46 species, although still lengthy because of the expectations of regulatory bodies, which are slower to accept advances in scientific knowledge. The list includes five Vachellia species, six “Mimoseae” species and 26 Acacia species. The number species from legume subfamilies other than the new Caesalpinioideae is greatly reduced.

Effect of simulated herbivory on bellyache bush (Jatropha gossypiifolia L.) growth and implications for biological control

Understanding the ability of invasive plants to compensate for herbivory damage is crucial for their management, but this has been poorly studied in weed biological control. Bellyache bush (Jatropha gossypiifolia L.) is an invasive weed and a target for biological control in Australia. To understand the response of bellyache bush to herbivory, we simulated herbivory damage, under field conditions, at a site in north Queensland. Two size classes, that is, seedlings and mature plants were subjected to either defoliation, shoot damage or a combination of both, and the damage was inflicted once, twice or thrice at 6–7 weeks interval. All herbivory types significantly reduced growth and biomass when herbivory was inflicted twice or thrice, whereas the single application had limited impact. Shoot damage alone and defoliation + shoot damage had a greater negative impact than defoliation treatment on plant height, basal stem diameter, the number of leaves, root length and the number of shoot tips produced while increasing the number of dead shoot tips. Defoliation alone and defoliation + shoot damage had a greater negative impact on the number of flowers and fruit pods produced than shoot damage. The greater negative effects noticed when herbivory was inflicted twice or thrice suggest that multivoltine biological control agents that can inflict shoot damage and defoliation should be sought for the biological control of bellyache bush.

Weevils as Targets for Biological Control, and the Importance of Taxonomy and Phylogeny for Efficacy and Biosafety

Curculionidae are a large mainly herbivorous family of beetles, some of which have become crop pests. Classical biological control has been attempted for about 38 species in 19 genera, and at least moderate success has been achieved in 31 % of cases. Only two weevil species have been considered to be completely controlled by a biological control agent. Success depends upon accurately matching natural enemies with their hosts, and hence taxonomy and phylogeny play a critical role. These factors are discussed and illustrated with two case studies: the introduction of the braconid parasitoid Mictroctonus aethiopoides into New Zealand for biological control of the lucerne pest Sitona discoideus, a case of complex phylogenetic relationships that challenged the prediction of potential non-target hosts, and the use of a mymarid egg parasitoid, Anaphes nitens, to control species of the eucalypt weevil genus Gonipterus, which involves failure to match up parasitoids with the right target amongst a complex of very closely related species. We discuss the increasing importance of molecular methods to support biological control programmes and the essential role of these emerging technologies for improving our understanding of this very large and complex family.

Analyses of nine years of citizen-based biological control monitoring of Dalmatian toadflax, Linaria dalmatica (Plantaginaceae) in Idaho, USA

Dalmatian toadflax has been a target for biological control in North America since the 1960s. The stem-mining weevil Mecinus janthiniformis was first released in Canada and the western United States in the mid-1990s. Since 2007, a citizen-based monitoring program in Idaho, USA has supplemented data collection to help evaluate the impact of M. janthiniformis on Dalmatian toadflax abundance and assess changes in the surrounding plant community. We monitored and analysed trends in toadflax, weevil, and the plant community abundance following weevil releases at the regional and site level (34 sites) across the state of Idaho, USA. Significant declines in toadflax cover and stem density were recorded across the majority of sites. Weevil populations have established at all release sites. The mechanistic model indicated that the population dynamics of toadflax at our sites are negatively affected by M. janthiniformis abundance. When averaged across the region, 15 years after weevil release, Dalmatian toadflax stem density and cover declined by 93 and 84%, respectively. We observed significant declines in toadflax abundance in over 75% of the sites. Changes to the surrounding plant community following weevil releases were less consistent among sites. At the regional scale we found evidence for an overall increase in average cover of native perennial grasses and other exotic weeds (primarily annual grasses and exotic forbs) but a decline in native forbs.

Assessing the status of biological control as a management tool for suppression of invasive alien plants in South Africa

Background: Biological control of invasive alien plants (IAPs) using introduced natural enemies contributes significantly to sustained, cost-effective management of natural resources in South Africa. The status of, and prospects for, biological control is therefore integral to National Status Reports (NSRs) on Biological Invasions, the first of which is due in 2017. Objectives: Our aim was to evaluate the status of, and prospects for, biological control of IAPs in South Africa. We discuss expansion of biological control and suggest indicators to be used in the upcoming NSR to assess sufficient growth. Method: We used published literature, unpublished work and personal communication to assess the status of biological control of IAPs. We propose indicators based on the targets for biological control that were proposed in the 2014 ‘National Strategy for dealing with biological invasions in South Africa’. To prioritise targets for future efforts, we used published lists of damaging IAPs and assessed the prospects for their biological control. Recommendations for using biological control as a management tool were made after discussion among the authors and with colleagues. Results: Significant control of several Cactaceae, Australian Acacia species and floating aquatic plants, and many other IAPs has been achieved in South Africa since 1913. Recently, biological control has benefited from improved international collaboration, a streamlined application process for the release of new biological control agents (resulting in the approval of 19 agents against 13 IAP species since 2013), and increased funding and capacity. There is still a need to improve implementation and to better integrate biological control with other control methods. In order to maximise benefits from biological control, increased investment is required, particularly in implementation and post-release evaluation, and in targeting new IAPs. Proposed targets for growth between 2017 and 2020 include an increase in financial investment in research by 29%, implementation by 28% and mass-rearing by 68%. Research capacity should increase by 29%, implementation capacity by 63% and mass-rearing capacity by 61%. New research projects should be initiated on 12 new IAP targets, while post-release monitoring efforts should be expanded to another 31 IAPs. Conclusion: Biological control of IAPs has contributed substantially to their management in South Africa, and continues to do so. Further investment in targeted aspects of IAP biological control will increase this contribution.

Thermal tolerance of Liothrips tractabilis, a biological control agent of Campuloclinium macrocephalum recently established in South Africa

AbstractThe South American herb Campuloclinium macrocephalum (Less.) DC. (Asteraceae; pompom weed), which invades grasslands, savannas, and wetlands in South Africa, is a recent target for biological control. A foliage‐deforming thrips, Liothrips tractabilis Mound & Pereyra (Thysanoptera: Phlaeothripidae), was released in South Africa in 2013, following confirmation of its host specificity and damage potential in quarantine. However, weed biocontrol agents sometimes fail to establish or have the desired impact because they are poorly suited to the climate of the new range. Thermal tolerance trials, within the range of 15–32.5 °C, were conducted prior to the thrips’ release to determine its developmental threshold and to generate a degree‐day model to highlight areas best suited for its establishment in South Africa. These laboratory data were validated by outdoor trials. The thrips completed development from egg to adulthood at all except the lowest and highest laboratory test temperatures, with developmental duration decreasing with increasing temperature. The lower developmental threshold was estimated at 9.6 °C with 546.9 degree days required to complete development. Within the regions invaded by C. macrocephalum in South Africa, the thrips was predicted to complete 3–9 annual generations. Developmental times in the outdoor trials were largely consistent with those in the laboratory. Liothrips tractabilis is largely compatible with the broader South African climate and seems likely to establish and proliferate on C. macrocephalum populations throughout the country. These predictions have partially been verified in that L. tractabilis has become established at several sites in South Africa, many of these in colder, high‐altitude areas which were predicted to support fewer annual generations.

Genomic evidence for plant-parasitic nematodes as the earliest Wolbachia hosts.

Wolbachia, one of the most widespread endosymbionts, is a target for biological control of mosquito-borne diseases (malaria and dengue virus), and antibiotic elimination of infectious filarial nematodes. We sequenced and analyzed the genome of a new Wolbachia strain (wPpe) in the plant-parasitic nematode Pratylenchus penetrans. Phylogenomic analyses placed wPpe as the earliest diverging Wolbachia, suggesting two evolutionary invasions into nematodes. The next branches comprised strains in sap-feeding insects, suggesting Wolbachia may have first evolved as a nutritional mutualist. Genome size, protein content, %GC, and repetitive DNA allied wPpe with mutualistic Wolbachia, whereas gene repertoire analyses placed it between parasite (A, B) and mutualist (C, D, F) groups. Conservation of iron metabolism genes across Wolbachia suggests iron homeostasis as a potential factor in its success. This study enhances our understanding of this globally pandemic endosymbiont, highlighting genetic patterns associated with host changes. Combined with future work on this strain, these genomic data could help provide potential new targets for plant-parasitic nematode control.

De Novo Analysis of the Transcriptome of Meloidogyne enterolobii to Uncover Potential Target Genes for Biological Control.

Meloidogyne enterolobii is one of the obligate biotrophic root-knot nematodes that has the ability to reproduce on many economically-important crops. We carried out de novo sequencing of the transcriptome of M. enterolobii using Roche GS FLX and obtained 408,663 good quality reads that were assembled into 8193 contigs and 31,860 singletons. We compared the transcripts in different nematodes that were potential targets for biological control. These included the transcripts that putatively coded for CAZymes, kinases, neuropeptide genes and secretory proteins and those that were involved in the RNAi pathway and immune signaling. Typically, 75 non-membrane secretory proteins with signal peptides secreted from esophageal gland cells were identified as putative effectors, three of which were preliminarily examined using a PVX (pGR107)-based high-throughput transient plant expression system in Nicotiana benthamiana (N. benthamiana). Results showed that these candidate proteins suppressed the programmed cell death (PCD) triggered by the pro-apoptosis protein BAX, and one protein also caused necrosis, suggesting that they might suppress plant immune responses to promote pathogenicity. In conclusion, the current study provides comprehensive insight into the transcriptome of M. enterolobii for the first time and lays a foundation for further investigation and biological control strategies.

Experts know more than just facts: eliciting functional understanding to help prioritise weed biological control targets

Prioritising investments in classical weed biological control (biocontrol) is a common decision-making challenge: biocontrol programmes can yield substantial benefits but are typically long-term and costly, and the outcome uncertain. Experts are often relied upon to help, but their role is generally restricted to providing facts and judgements to populate an existing prioritisation model, which in turn receives little scrutiny. We developed and applied a new prioritisation framework to guide biocontrol investment decisions by livestock industries that required eliciting experts’ functional understanding (including their in-depth knowledge of the theoretical and practical drivers of weed biocontrol programmes). This consultative and transparent framework drew on expertise from most biocontrol practitioners in Australia through a structured workshop, and the literature. Each of the 75 weed taxa considered was placed in a matrix according to their impact (current or potential) and the prospects of biocontrol achieving pre-defined management goals. There was considerable knowledge uncertainty regarding potential impacts, which is of concern when making pre-emptive investments. Feasibility (likelihood of finding host-specific agents) and likelihood of success (management goals being met, assuming that host-specific agents are available) of biocontrol were both assessed as low for 51 % of taxa. Predicted barriers to successful biocontrol were diverse and idiosyncratic, suggesting that application of more quantitative prioritisation approaches would be challenging. A short-list of 13 weed taxa was identified for further consideration as biocontrol targets, based on the trade-off between potential impact and prospects for biocontrol. Research priorities emerged from the prioritisation process that would maximise investment outcomes for each taxon. Only two short-listed taxa are new targets, reflecting the maturity of the biocontrol discipline targeting weeds of livestock industries in Australia. Accessing the in-depth functional understanding of experts resulted in explicit characterisation of the barriers to successful biocontrol and if/how they might be overcome, improved characterisation of uncertainty, and provided directed guidance for investment. Such an approach would be readily applicable to analogous decision-making challenges in other sectors and countries.