Chlorophyll fluorometry as a method of determining the effectiveness of a biological control agent in post-release evaluations

ABSTRACT

The impact of the planthopper Megamelus scutellaris, a biocontrol agent of water hyacinth in South Africa, was assessed using chlorophyll fluorometry in a greenhouse study under two different eutrophic nutrient treatments and agent densities (high and low). The results indicated that plants grown in low nutrients with high densities of M. scutellaris showed the greatest reduction in the fluorescence parameters Fv/Fm and PI_abs. The successful use of chlorophyll fluorometry for the detection of subtle insect damage to water hyacinth leaves could have future application in post-release studies to measure the impact of M. scutellaris in the field.     

Megamelus scutellaris (Hemiptera: Delphacidae), a biocontrol agent of water hyacinth,is not sufficiently specific for release in Australia

Water hyacinth Eichhornia crassipes (Pontederiaceae) is one of the world's worst invasive species, responsible for damaging aquatic systems in many warmer parts of the globe including north America, Africa, Asia and Australia. The planthopper Megamelus scutellaris Berg (Delphacidae) has been released in USA and approved for release in South Africa for biocontrol of water hyacinth. We assessed this agent for suitability for release in Australia and found that a related native aquatic plant, Monochoria cyanea (Pontederiaceae) is within the fundamental host range of this insect. Adult survival, oviposition and development of nymphs to adult was equally high on M. cyanea as on the target species, although the quality of these next generation adults was lower than those reared on the target species. This demonstrates that M. scutellaris is not sufficiently specific for release in Australia. Nymphal development to adults occurred only in very low numbers on the three other Australian species of Monochoria. M. cyanea only occurs in Australia so M. scutellaris is still a possible water hyacinth biocontrol candidate for other regions depending on the results of assessment of the risk to local species of Monochoria. This study demonstrates the effectiveness of modern biocontrol agent assessment and reinforces the importance of testing of local non-target species.     

Feeding behavior and spatial distribution of two planthoppers,Megamelus scutellaris (Delphacidae) and Taosa longula (Dictyopharidae), on water hyacinth

Megamelus scutellaris Berg (Delphacidae) and Taosa (Cuernavaca) longula Remes Lenicov (Dictyopharidae) are specialist planthoppers that feed and reproduce on the invasive aquatic weed, Eichhornia crassipes (Martius) Solms-Laubach (Pontederiaceae). They overlap geographically in several regions of South America and may, therefore, interact and compete for food and microhabitat. Preliminary observations indicated that both species do not feed on the same part of the plant. We hypothesized that they partition the resource; hence, we studied (1) the feeding mechanism at the tissue level and (2) the spatial distribution of both species on the water hyacinth plant. Salivary sheaths were detected through histological sections of plant tissues using light microscopy. The location of either planthopper species on the plant was recorded when in the presence or absence of the other species. Both species produced true salivary sheaths, mostly branched (M. scutellaris: 82%; T. longula: 84%), ending in phloem (M. scutellaris: 56%; T. longula: 52%), and xylem tissues (M. scutellaris: 24%; T. longula: 28%). They resided on different parts of the water hyacinth plant even when they did not coexist; nymphs of T. longula occurred primarily on the back side of the leaf laminas, while nymphs of M. scutellaris occupied the basal zone of the petioles. This study shows that these planthoppers complement each other and could be used in combination as control agents for water hyacinth. Further experimental studies and field observations are necessary to quantify interactions.     

Comparisons of the thermal physiology of water hyacinth biological control agents: predicting establishment and distribution pre‐ and post‐release

Investigations into the thermal physiology of weed biological control agents may elucidate reasons for establishment failure following release. Such studies have shown that the success of water hyacinth biological control in South Africa remains variable in the high‐lying interior Highveld region, because the control agents are restricted to establishment and development due to extreme winter conditions. To determine the importance of thermal physiology studies, both pre‐ and post‐release, this study compared the known thermal requirements of Eccritotarsus catarinensis (Carvalho) (Hemiptera: Miridae) released in 1996, with those of an agent released in 1990, Niphograpta albiguttalis (Warren) (Lepidoptera: Pyralidae) and a candidate agent, Megamelus scutellaris Berg (Hemiptera: Delphacidae), which is currently under consideration for release. The lower developmental threshold (t_o) and rate of development (K) were determined for N. albiguttalis and M. scutellaris, using a reduced axis regression, and incorporated into a degree‐day model which compared the number of generations that E. catarinensis, N. albiguttalis, and M. scutellaris are capable of producing annually at any given site in South Africa. The degree‐day models predicted that N. albiguttalis (K = 439.43, t_o = 9.866) can complete 4–11 generations per year, whereas M. scutellaris (K =502.96, t_o = 11.458) can only complete 0–10 generations per year, compared with E. catarinensis (K = 342, t_o = 10.3) which is predicted to complete 3–14 generations per year. This suggests that the candidate agent, M. scutellaris, will not fare better in establishment than the other two agents that have been released in the Highveld, and that it may not be worth releasing an agent with higher thermal requirements than the agents that already occur in these high‐lying areas. Thermal physiology studies conducted prior to release are important tools in biological control programmes, particularly those in resource‐limited countries, to prevent wasting efforts in getting an agent established.     

Cryptic species of a water hyacinth biological control agent revealed in South Africa: host specificity,impact, and thermal tolerance

The discovery that cryptic species are more abundant than previously thought has implications for weed biological control, as there is a risk that cryptic species may be inadvertently released with consequences for the safety of the practice. A cryptic species of a biological control agent released for the control of the invasive alien macrophyte, water hyacinth, Eichhornia crassipes (C. Mart.) Solms. (Pontederiaceae), was recently discovered in South Africa. The two species were considered a single species prior to genetic analysis and interbreeding experiments. The original biological control agent retains the name Eccritotarsus catarinensis (Carvalho) (Heteroptera: Miridae) whereas the new species has been described as Eccritotarsus eichhorniae Henry. In this study, we compared the host specificity, efficacy, and thermal physiologies of the two species. The host specificity of the two species within the Pontederiaceae was very similar and both are safe for release in South Africa. Comparison of the per capita impact of the two species indicated that E. eichhorniae was the more damaging species but this is likely to be influenced by temperature, with E. catarinensis being more effective under lower temperatures and E. eichhorniae being more effective under higher temperatures. Releasing the correct species for the thermal environment of each release site will improve the level of control of water hyacinth in South Africa. This example highlights the need to keep populations of biological control agents from different native range collection localities separate, and to screen for host specificity and efficacy.     

Toxic effect of herbicides used for water hyacinth control on two insects released for its biological control in South Africa

The integrated control of water hyacinth, Eichhornia crassipes (Martius) Solms-Laubach (Pontederiaceae) has become necessary in South Africa, as biological control alone is perceived to be too slow in controlling the weed. In total, seven insect biological control agents have been released on water hyacinth in South Africa. At the same time, herbicides are applied by the water authorities in areas where the weed continues to be troublesome. This study investigated the assumption that the two control methods are compatible by testing the direct toxicity of a range of herbicide formulations and surfactants on two of the biological control agents released against water hyacinth, the weevil, Neochetina eichhorniae Warner (Coleoptera: Curculionidae) and the water hyacinth mirid, Eccritotarsus catarinensis (Carvalho) (Hemiptera: Miridae). A number of the formulations used resulted in significant mortality of the mirid and the weevil. Products containing 2,4-D amine and diquat as active ingredients caused higher mortality of both agents (up to 80% for the mirid) than formulations containing glyphosate. Furthermore, when surfactants were added to enhance herbicide efficiency, it resulted in increased toxicity to the insects. We recommend that glyphosate formulations should be used in integrated control programmes, and that surfactants be avoided in order to reduce the toxic nature of spray formulations to the insect biological control agents released against water hyacinth.     

Biological control of water hyacinth in California’s Sacramento–San Joaquin River Delta: observations on establishment and spread

Water hyacinth (Eichhornia crassipes (Martius) Solms-Laubach) is a serious invasive weed in the Sacramento–San Joaquin River Delta of California. Three insects: Neochetina eichhorniae Warner and Neochetina bruchi Hustache (Coleoptera: Curculionidae) and Niphograpta (=Sameodes) albiguttalis (Warren) (Lepidoptera: Crambidae) were released during 1982–1987 at four locations for the biological control of water hyacinth. Observations in 1985 suggested that all three species had established. By 2002, water hyacinth populations in the Delta still required an aggressive chemical control campaign and the status of the biological control agents was in question. In late 2002, a field survey to determine the distribution and abundance of the released insects was performed. Water hyacinth plants were collected by boat in the main water channels and from land at smaller sloughs and examined for insects. In total, 27 sites with water hyacinth distributed across the Delta were examined of which 21 had weevils. Weevil abundance ranged from 0 to 10.9 weevils per plant, with an average of 0.93 (±0.47 SEM) adult weevils per plant. All weevils (n?=?518) were identified as N. bruchi. No N. eichhorniae were recovered and no larvae or evidence of larval feeding by N. albiguttalis were observed. A total of 322 weevils were examined for microsporidia and none was found infected, indicating an infection rate of less than 1%. These results suggest that N. bruchi may be the only established biological control agent of water hyacinth in the Delta and that infection by microsporidia does not appear to be limiting its population abundance.     

Two in one: cryptic species discovered in biological control agent populations using molecular data and crossbreeding experiments

There are many examples of cryptic species that have been identified through DNA‐barcoding or other genetic techniques. There are, however, very few confirmations of cryptic species being reproductively isolated. This study presents one of the few cases of cryptic species that has been confirmed to be reproductively isolated and therefore true species according to the biological species concept. The cryptic species are of special interest because they were discovered within biological control agent populations. Two geographically isolated populations of Eccritotarsus catarinensis (Carvalho) [Hemiptera: Miridae], a biological control agent for the invasive aquatic macrophyte, water hyacinth, Eichhornia crassipes (Mart.) Solms [Pontederiaceae], in South Africa, were sampled from the native range of the species in South America. Morphological characteristics indicated that both populations were the same species according to the current taxonomy, but subsequent DNA analysis and breeding experiments revealed that the two populations are reproductively isolated. Crossbreeding experiments resulted in very few hybrid offspring when individuals were forced to interbreed with individuals of the other population, and no hybrid offspring were recorded when a choice of mate from either population was offered. The data indicate that the two populations are cryptic species that are reproductively incompatible. Subtle but reliable diagnostic characteristics were then identified to distinguish between the two species which would have been considered intraspecific variation without the data from the genetics and interbreeding experiments. These findings suggest that all consignments of biological control agents from allopatric populations should be screened for cryptic species using genetic techniques and that the importation of multiple consignments of the same species for biological control should be conducted with caution.     

The role of eutrophication in the biological control of water hyacinth, <Emphasis Type="Italic">Eichhornia crassipes</Emphasis>, in South Africa

South Africa has some of the most eutrophic aquatic systems in the world, as a result of the adoption of an unnecessarily high 1 mg l⁻¹ phosphorus (P) standard for all water treatment works in the 1970 s. The floating aquatic macrophyte, water hyacinth (Eichhornia crassipes (Mart.) Solms (Pontederiaceae)), has taken advantage of these nutrient rich systems, becoming highly invasive and damaging. Despite the implementation of a biological control programme in South Africa, water hyacinth remains the worst aquatic weed. A meta-analysis of published and unpublished laboratory studies that investigated the combined effect of P and nitrogen (N) water nutrient concentration and control agent herbivory showed that water nutrient status was more important than herbivory in water hyacinth growth. Analysis of long-term field data collected monthly from 14 sites around South Africa between 2004 and 2005 supported these findings. Therefore the first step in any water hyacinth control programme should be to reduce the nutrient status of the water body.     

Fungi associated with Eichhornia crassipes in South Africa and their pathogenicity under controlled conditions

Eichhornia crassipes Mart. Solms-Laubach (Pontederiaceae), water hyacinth, continues to be the world's worst aquatic weed. In South Africa, considerable research has been conducted on biological control agents associated with water hyacinth, with the release of six arthropods and one fungus, but little is known about the occurrence and impacts of native phytopathogenic fungi. Nation-wide surveys were conducted in 2010 and 2011 on various aquatic bodies of South Africa to identify the fungal pathogens associated with water hyacinth. Diseased plant parts were collected and fungi were isolated and identified. Some 250 isolates belonging to more than 25 genera were collected. Some of these represent new host records, as well as undescribed taxa. Isolates of Acremonium zonatum (Sawada) Gams, Alternaria eichhorniae Nag Raj and Ponnappa, Bipolaris hawaiiensis (M.B. Ellis) Uchida and Aragaki, Fusarium Link, Myrothecium roridum Tode ex Fr. and Ulocladium sp., showed the highest pathogenicity and have the potential to be useful in complementing the ongoing biocontrol programme on water hyacinth in South Africa.     

Assessing the true status of the fish species Labeo cylindricus (Peters 1868) (Teleostei: Cyprinidae) in Lake Baringo,Kenya

Eutrophication contributes to the proliferation of alien invasive weed species such as water hyacinth Eichhornia crassipes. Although the South American moth Niphograpta albiguttalis was released in South Africa in 1990 as a biological control agent against water hyacinth, no post-release evaluations have yet been conducted here. The impact of N. albiguttalis on water hyacinth growth was quantified under low-, medium- and high-nutrient concentrations in a greenhouse experiment. Niphograpta albiguttalis was damaging to water hyacinth in all three nutrient treatments, but significant damage in most plant parameters was found only under high-nutrient treatments. However, E. crassipes plants grown in high-nutrient water were healthier, and presumably had higher fitness, than plants not exposed to herbivory at lower-nutrient levels. Niphograpta albiguttalis is likely to be most damaging to water hyacinth in eutrophic water systems, but the damage will not result in acceptable levels of control because of the plant's high productivity under these conditions. Niphograpta albiguttalis is a suitable agent for controlling water hyacinth infestations in eutrophic water systems, but should be used in combination with other biological control agents and included in an integrated management plan also involving herbicidal control and water quality management.     

Predicting the distribution of Eccritotarsus catarinensis, a natural enemy released on water hyacinth in South Africa

Water hyacinth [Eichhornia crassipes (Mart.) Solms (Pontederiaceae)] is the most damaging aquatic weed in South Africa, where five arthropod biological control agents have been released against it. The most recent introduction of Eccritotarsus catarinensis (Carvalho) (Heteroptera: Miridae) has failed to establish permanent populations at a number of sites in South Africa where water hyacinth is a problem. Cold winter temperatures at these sites are assumed to be the reason for these establishment failures. This assumption was tested by investigating the thermal physiology of the mirid, then incorporating these data into various predictive distribution models. Degree‐day models predict 3–14 generations per year at different localities in South Africa, and five generations at a Johannesburg site where the mirid failed to overwinter. The inability to develop sufficiently rapidly during winter months may hinder overwintering of this insect, which was predicted to develop through only one generation during the winter months of April to August in Johannesburg. A CLIMEX model also showed that cold stress limits the mirid's ability to overwinter in the interior of the country, while determination of the lower lethal limit (–3.5 °C) and critical thermal minimum (1.2 ± 1.17 °C) also indicated that extreme temperatures will limit establishment at certain sites. It is concluded that E. catarinensis is limited in its distribution in South Africa by low winter temperatures.     

Invaded habitat incompatibility affects the suitability of the potential biological control agent Listronotus sordidus for Sagittaria platyphylla in South Africa

Sagittaria platyphylla (Engelmann) J.G. Smith (Alismataceae) was first recorded in South Africa in 2008 and is considered to be an emerging weed with naturalised populations occurring throughout the country. A biological control programme was initiated in Australia and surveys conducted between 2010 and 2012 yielded potential agents, including the crown feeding weevil, Listronotus sordidus Gyllenhal (Coleoptera: Curculionidae). The potential of L. sordidus as a candidate biological control agent against S. platyphylla in South Africa was examined. Although adult feeding was recorded on a number of plant species, oviposition and larval development indicated a narrow host range restricted to the Alismataceae. In South Africa, S. platyphylla populations are primarily found in inundated systems. However, laboratory studies showed that L. sordidus did not oviposit on inundated plants, potentially nullifying the impact of the insect on South African populations. It is suggested that even though L. sordidus is a damaging, specific agent, its limited impact on inundated plant populations in South Africa does not justify the inherent risk associated with the release of a biological control agent.     

Genetic diversity of introduced populations of the water hyacinth biological control agent Eccritotarsus catarinensis (Hemiptera: Miridae)

Genetic bottlenecks can be deleterious to populations. In biological control, agent populations may be subject to severe bottlenecks during selection, importation and while in culture. The genetic variability of two collections of the water hyacinth biological control agent Eccritotarsus catarinensis Carvalho (Hemiptera: Miridae) was measured using Inter-simple Sequence Repeats (ISSR) and mtDNA cytochrome oxidase I (COI) sequences. The first collection (Brazilian) went through a bottleneck of a single gravid female, while the second collection (Peru) originated from 1000 individuals and has been maintained at a large size in culture. Two naturalised South African populations from the Brazilian collection were also sampled (Nseleni and Mbozambo). Polymorphism for ISSR was high in the Peruvian and two naturalised samples, but much less so in the Brazilian sample. The Peruvian population was shown to be highly differentiated from the Brazilian and its naturalised populations by high values of F_ST and Nei’s genetic distance, as well as in a Multidimensional Scaling (MDS) plot and an unrooted neighbour joining tree derived from Jaccard’s coefficient of similarity. In addition, sequencing of the COI region of the mitochondrial DNA revealed only two haplotypes, one Brazilian and one Peruvian, with a 5.2% sequence divergence, suggesting that recombination and not mutation is the cause of most variation in the ISSR regions. The results suggest that substantial genetic variation may be retained or recovered after a bottleneck. This may mitigate deleterious effects that are a concern for the fate of biological control agents after release.     

Abundance,composition and spatial variation in the egg bank of a tropical zooplankton community

The semi‐aquatic grasshopper Cornops aquaticum (Bruner, 1906) is native to South America, with a distribution from the Argentinian pampas to the Gulf of Mexico, and is currently being proposed as a biological control agent for the invasive water hyacinth (Eichhornia crassipes) in South Africa. This study reports results of a neutral molecular marker (microsatellites) study on C. aquaticum within its native range. The data were analysed for levels of diversity and structure within/between South American populations, and correlations between host plant, geography and environmental/climatic variables were investigated. We found no evidence to support associations between host plant use and microsatellite genotypes (hypothesis 1). High levels of gene flow and weak genetic clustering of populations indicate a lack of differentiation, therefore an interaction between climate and local genotype (hypothesis 2) seems unlikely. Our results suggest that C. aquaticum may not have “tightly” coevolved with its host Eichhornia spp. (Pontederiaceae) as originally thought, and that instar variation might be due to the effect of local climate on phenotype (hypothesis 3) or possibly a locally adaptive trait.     

Testing the thermal limits of Eccritotarsus catarinensis: a case of thermal plasticity

Water hyacinth is considered the most damaging aquatic weed in South Africa. The success of biocontrol initiatives against the weed varies nation-wide, but control remains generally unattainable in higher altitude, temperate regions. Eccritotarsus catarinensis (Hemiptera: Miridae) is a biocontrol agent of water hyacinth that was first released in South Africa in 1996. By 2011, it was established at over 30 sites across the country. These include the Kubusi River, a site with a temperate climate where agent establishment and persistence was unexpected. This study compared the critical thermal limits of the Kubusi River insect population with a laboratory-reared culture to determine whether any physiological plasticity was evident that could account for its unexpected establishment. There were no significant differences in critical thermal maxima (CT_max) or minima (CT_min) between sexes, while the effect of rate of temperature change on the thermal parameters in the experiments had a significant impact in some trials. Both CT_max and CT_min differed significantly between the two populations, with the field individuals tolerating significantly lower temperatures (CT_min: ?0.3°C?±?0.063 [SE], CT_max: 42.8°C?±?0.155 [SE]) than those maintained in the laboratory (CT_min: 1.1°C?±?0.054 [SE], CT_max: 44.9°C?±?0.196 [SE]). Acclimation of each population to the environmental conditions typical of the other for a five-day period illustrated that short-term acclimation accounted for some, but not all of the variation between their lower thermal limits. This study provides evidence for the first cold-adapted strain of E. catarinensis in the field, with potential value for introduction into other colder regions where water hyacinth control is currently unattainable.     

Should the mirid,Eccritotarsus catarinensis (Heteroptera: Miridae), be considered for release against water hyacinth in the United States of America?

Between one and seven biological control agents have been released against water hyacinth (Eichhornia crassipes (Mart.) Solms) in at least 30 countries, with varied success. A mirid, Eccritotarsus catarinensis (Carvalho) (Heteroptera: Miridae), the most recent agent released, is damaging to the plant on the African continent. It could be useful in the USA where water hyacinth remains a problem, but its introduction remains in doubt because during host specificity trials, it developed on Pontederia cordata L. (pickerelweed), indigenous to the USA. However, it did not establish on pickerelweed monocultures during South African field trials, and only light spillover feeding occurred where the two plants coexisted suggesting that the use of P. cordata as a host is a laboratory artefact and it may be suitable for use in the USA, if its thermal physiology allows establishment. We reran models developed for South Africa using CLIMEX to predict whether the mirid will establish where water hyacinth and pickerelweed co-occur, but not where pickerelweed occurs in the absence of water hyacinth. The models suggest that the mirid's distribution will be limited by cold winter temperatures and insufficient thermal accumulation to the southern states of the USA, within the main distribution of water hyacinth. Even though some spillover feeding on pickerelweed might result where the two plants co-occur, the risk of population level effects seems minimal and the risk to more northern pickerelweed negligible. The benefits, including improved habitat for pickerelweed, associated with further suppression of water hyacinth, outweigh the minimal risk of collateral damage to pickerelweed.     

Thermal plasticity and microevolution enhance establishment success and persistence of a water hyacinth biological control agent

Aspects of the thermal physiology of the water hyacinth biological control agent Eccritotarsus catarinensis Carvalho (Hemiptera: Miridae) have been extensively investigated over the past 20 years to understand and improve post‐release establishment in the field. Thermal physiology studies predicted that the agent would not establish at a number of cold sites in South Africa, where it has nonetheless subsequently established and thrived. Recently, studies have begun to incorporate the plastic nature of insect thermal physiology into models of agent establishment. This study determined whether season and locality influenced the thermal physiology of two field populations of E. catarinensis, one collected from the hottest site where the agent has established in South Africa, and one from the coldest site. The thermal physiology of E. catarinensis was significantly influenced by season and site, demonstrating a degree of phenotypic plasticity, and that some post‐release local adaptation to climatic conditions has occurred through microevolution. We then determined whether cold acclimation under laboratory conditions was possible. Successfully cold‐acclimated E. catarinensis had a significantly lower critical thermal minimum (CT_min) compared to the field cold‐acclimated population. This suggests that cold acclimation of agents could be conducted in the laboratory before future releases to improve their cold tolerance, thereby increasing their chance of establishment at cold sites and allowing further adaptation to colder climates to occur in the field. Although the thermal tolerance of E. catarinensis is limited by local adaptations to climatic conditions in the native range, the plastic nature of the insect's thermal physiology has allowed it to survive in the very different climatic conditions of the introduced range, and there has been some adaptive change to the insect's thermal tolerance since establishment. This study highlights the importance of plasticity and microevolutionary processes in the success of biological control agents under the novel climatic conditions in the introduced range.     

The effects of insect–insect interactions on the performance of three biological control agents released against water hyacinth

Insect–insect interactions can have implications for biological control programmes when multiple agent species are released. In many cases there is an increase in the efficacy when more than one species is used; however, there is a possibility that releasing an additional species into a programme could have a negative effect. The interactions between three arthropod agents of water hyacinth Eichhornia crassipes (Martius) Solms-Laubach, Eccritotarsus catarinensis (Carvalho), Neochetina bruchi Hustache and Neochetina eichhorniae Warner were investigated in an experiment to measure the impact that pairwise combinations of the insects may have on their performance. There was a significant interaction between the mirid E. catarinensis and the weevil N. eichhorniae, with significantly fewer weevil feeding scars when in combination with the mirid (approximately 0.2 scars per cm²) than when alone (approximately 0.4 scars per cm²). There were also slightly fewer petioles mined by N. eichhorniae when in combination with the mirid. Interestingly there was a negative interaction between the two weevil species when in combination, with the number of feeding scars being significantly lower per individual when the two species were in combination. None of the insects performed significantly better when in combination with another insect, however, the mirid was never negatively affected by the presence of either weevil species. The interactions observed between the insects tested were identifiable but subtle and are unlikely to have implications on establishment or performance of the insects in the introduced range, South Africa.     

Biology and host range of Mada polluta,a potential biological control agent of Tecoma stans in South Africa

The host range of Mada polluta Mulsant (Coleoptera:Coccinnellidae) was studied to assess its suitability as a biological control agent of Tecoma stans (L.) Juss ex Kunth var stans (Bignoniaceae), an invasive weed in South Africa. Biology of M. polluta and its host range were determined in the laboratory using no-choice and multi-choice feeding, oviposition and larval survival tests. Out of 36 plant species from 12 plant families (Bignoniaceae, Acanthaceae, Asteraceae, Verbenaceae, Lamiaceae, Oleaceae, Cucurbitaceae, Fabaceae, Scrophulariaceae, Solanaceae, Apiaceae, Chenopodiaceae and Poaceae) within the order Lamiales that were tested during the host specificity testing, M. polluta showed a very strong preference for T. stans, depositing its eggs on T. stans and none on non-target plant species. In no-choice tests, an average of 246 eggs was laid on T. stans, and from these, 133 larvae developed to adulthood. The beetle also showed very promising biological attributes that will contribute to its success as a biological control agent of T. stans. These attributes include highly damaging larvae and adults, high fecundity (532 eggs/female) and a short life cycle (four weeks). The short life cycle will enable multiple generations per year and rapid population increase in the field. It is concluded that M. polluta is sufficiently host-specific to be released against T. stans in South Africa. It is, therefore, strongly recommended that permission be granted to release this beetle from quarantine for biological control of T. stans in South Africa.