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• Introduction The Eucalyptus Weevil (Gonipterus “scutellatus” Gyllenhal) is a notorious pest of eucalypt plantations around the world, but its host range differs across its area of introduction, which may be due to it being a complex of several cryptic species. • Objectives The performance of the weevil was tested on 14 Eucalyptus and one Syzygium species in the laboratory and the field in South Africa. • Results The Weevil exhibited different levels of polyphagy, depending on how the host plants were presented: as bouquets or sleeved branches, in choice or no-choice combinations or in the open field. The fundamental host range in the laboratory was found to be broader than the realized host range in the field. Eucalyptus smithii was found to be the preferred host while Eucalyptus saligna and the native Syzygium myrtifolia were immune to both feeding and oviposition. Adult feeding and oviposition were more selective in the field, and the larvae were found to be less discriminating than the adults. • Conclusions The weevil is shown to have a narrow host range within two sections of the subgenus Symphyomyrtus, a finding that could contribute to resolution of the taxonomy of the genus Eucalyptus. Further, it suggests that countries that already have the pest may be susceptible to introductions of additional Gonipterus species. KeywordsHost preference–Host specificity–Realized and fundamental host range–Resistant species
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... Among the eucalypt species regularly sampled in this study, there seems to be a preference for E. propinqua over E. dunnii as hosts of Gonipterus, given the higher number of egg capsules and adults found E. propinqua, with E. nicholii intermediate in preference. These results, however, must be interpreted locally, taking into account the eucalypt and Gonipterus species composition in the area before a conclusion regarding preference can be reached (Clarke et al., 1998;Newete et al., 2011). Studies of G. platensis and Gonipterus sp. ...
... Studies of G. platensis and Gonipterus sp. n. 2. have shown a general tendency of these species to prefer feeding on trees of the subgenus Symphyomyrtus, particularly those in the section Maidenaria (Newete et al., 2011;Gonçalves et al., 2019), to which E. dunnii and E. nicholii belong. E. propinqua, which belongs in the section Latoangulatae, has been shown to sustain G. sp. ...
... E. propinqua, which belongs in the section Latoangulatae, has been shown to sustain G. sp. n. 2 adult feeding but not oviposition (Newete et al., 2011). In our study, most adults found on E. propinqua were G. sp. ...
Article
Gonipterus is a genus of defoliating weevils that causes significant impact in commercially grown eucalypts in their native range in southern Australia and as invasive pests in Western Australia and several countries overseas. The diversity of species in this genus is still in the process of discovery, and in subtropical Australia, its diversity and ecological parameters are largely unknown. We surveyed Gonipterus phenology, species composition and trophic associations in South East Queensland, where little has been recorded about this genus. Surveys were conducted once a month in a non-commercial plantation of native eucalypts, where three species of trees were sampled regularly and others checked on an ad hoc basis. On each sampling occasion, adult weevils, larvae and egg capsules were collected, adults identified, larvae reared and egg capsules individualized in small containers for emergence of larvae and parasitoids. Two peaks of egg-laying occurred, whereas numbers of adults and larvae had only one peak each. Six species of Gonipterus were collected: two described but in need of revision, two undescribed but previously recognized and two undescribed and hitherto unrecognized, each with a different pattern of host–tree association. Three egg-parasitoid species, Anaphes nitens, Centrodora damoni and Euderus sp. were reared from egg capsules, varying in prevalence according to the tree species from which the eggs were collected.
... Threats from forest pests and diseases are of major apprehension to South Africa's commercial forestry sector (Oumar and Mutanga 2014). Gonipterus scutellatus, commonly known as the eucalyptus snout beetle, is a leaf-feeding pest that has spread throughout South Africa's commercial forests (Newete, Oberprieler, and Byrne 2011). The beetle is a specialist on the species eucalyptus (Newete, Oberprieler, and Byrne 2011), which are the most productive commercially planted tree species found in the country (Adam, Mutanga, and Ismail 2013). ...
... Gonipterus scutellatus, commonly known as the eucalyptus snout beetle, is a leaf-feeding pest that has spread throughout South Africa's commercial forests (Newete, Oberprieler, and Byrne 2011). The beetle is a specialist on the species eucalyptus (Newete, Oberprieler, and Byrne 2011), which are the most productive commercially planted tree species found in the country (Adam, Mutanga, and Ismail 2013). Therefore, managing the impacts of the beetle must be prioritized to mitigate its potential impacts. ...
... Therefore, managing the impacts of the beetle must be prioritized to mitigate its potential impacts. Attempts to control the beetle in South Africa were made in 1949 when the egg parasitic wasp Anaphes nitens was first used as a biological control measure (Newete, Oberprieler, and Byrne 2011;Tooke 1955). However, South Africa's environmental conditions still endorse the spread of the beetle, even in the presence of the wasp, therefore requiring alternative control and monitoring measures (Loch and Floyd 2001). ...
Article
Gonipterus scutellatus is a beetle causing severe defoliation to South Africa’s eucalyptus plantations. This defoliation induced by the beetle inhibits the eucalypts ability to photosynthesize, by affecting its chlorophyll content. Therefore, this study integrates spatially optimized and the single 0.5 m resolution vegetation indices with sparse partial least squares regression (SPLS-R) and partial least squares regression (PLS-R) to detect and map leaf chlorophyll content of defoliated eucalyptus plantations. The optimized vegetation indices were spatially resampled to resolutions that best paralleled varying levels of G. scutellatus defoliation. From the results, the 0.5 m resolution SPLS-R model (R ² = 0.76; RMSE of 1.50 (2.88% of the mean measured chlorophyll)) outcompeted the 0.5 m resolution PLS-R (R ² = 0.73; RMSE of 1.54 (2.95% of the mean measured chlorophyll)) model. Furthermore, the spatially optimized SPLS-R (R ² = 0.81; RMSE of 1.44 (2.76% of the mean measured chlorophyll) model was more superior in detecting and mapping chlorophyll content of defoliated eucalyptus plantations when compared to the 0.5 m resolution SPLS-R model. The most significant variables selected by the optimized SPLS-R model were DMI, ARI, NDRE, GNDVI, and NDVI. In essence, this study has illustrated the significance of the spatial resolution in effectively detecting and mapping chlorophyll content of defoliated eucalyptus plantations.
... An exception is Gonipterus sp. n. 2 in South Africa (Newete et al. 2011). Here, differences observed in field and laboratory trials indicated a difference in fundamental and realised host range and identified E. urophylla as part of the fundamental host range of Gonipterus sp. ...
... Here, differences observed in field and laboratory trials indicated a difference in fundamental and realised host range and identified E. urophylla as part of the fundamental host range of Gonipterus sp. n. 2 (Newete et al. 2011). This species is not frequently infested in South Africa and does not occur in the native range of Gonipterus sp. ...
... This species is not frequently infested in South Africa and does not occur in the native range of Gonipterus sp. n. 2 (Newete et al. 2011). It is used to develop hybrids in South Africa, where it is combined with E. grandis. ...
Article
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Gonipterus scutellatus (Coleoptera: Curculionidae), once thought to be a single species, is now known to reside in a complex of at least eight cryptic species. Two of these species (G. platensis and G. pulverulentus) and an undescribed species (Gonipterus sp. n. 2) are invasive pests on five continents. A single population of Anaphes nitens, an egg parasitoid, has been used to control all three species of Gonipterus throughout the invaded range. Limited knowledge regarding the different cryptic species and their diversity significantly impedes efforts to manage the pest complex outside the native range. In this review, we consider the invasion and taxonomic history of the G. scutellatus cryptic species complex and the implications that the cryptic species diversity could have on management strategies. The ecological and biological aspects of these pests that require further research are identified. Strategies that could be used to develop an ecological approach towards managing the G. scutellatus species complex are also suggested.
... Faced with significant economic losses, stakeholders are searching for alternative management strategies, such as biological control with alternative natural enemies or using eucalypt species that are less susceptible to G. platensis (Jactel et al. 2009;Richardson and Meakins 1986;Valente et al. 2017). Although several authors have focussed on host susceptibility to Gonipterus spp., such studies often dealt with distinct species within the snout beetle complex (Mapondera et al. 2012), resulting in discrepancies in literature (Newete et al. 2011). In countries where G. platensis is present, E. globulus is consistently found to be a preferred host, even though several other species have also been identified as susceptible, such as Eucalyptus camaldulensis Dehnh., E. grandis W.Hill, E. longifolia Link, E. obliqua L'Hér., E. propinqua Deane & Maiden, E. robusta Sm., and E. viminalis Labill. ...
... Closely related plants are likely to share traits that make them similarly acceptable to a particular phytophagous insect (Bertheau et al. 2010;Branco et al. 2014a;Östrand et al. 2008) and this seems to hold true for the snout beetle. In South Africa, Newete et al. (2011) found that Gonipterus sp. n. 2 (sensu Mapondera et al. 2012) also preferred to feed on eucalypts from section Maidenaria. ...
... Traits like pest survival, food consumption, or weight gain were consistently higher in host species preferred under field conditions, such as E. globulus, E. smithii, or E. badjensis, and lower in the least preferred species. However, under experimental conditions, when insects are forced to feed on a particular plant species, they may use hosts that they would normally not use in the field (Newete et al. 2011;Palmer and Goeden 1991). Indeed, in our study, G. platensis never fed on E. regnans whenever an alternative host was accessible, but some consumption occurred in the no-choice test. ...
Article
• Key message Gonipterus platensis is an important insect pest of eucalypt plantations. Despite biological control by the egg parasitoid Anaphes nitens , economic losses remain high in several areas outside its native range where susceptible eucalypt species are grown in commercial plantations. The susceptibility to G. platensis of 17 Eucalyptus species was evaluated and possible alternatives for reforestation in high pest incidence areas were identified. • Context Gonipterus platensis is an important pest of Eucalyptus worldwide. Despite biological control, it causes significant losses to Eucalyptus plantations in several areas, requiring alternative management options. • Aims We analysed host preference of G. platensis towards 17 Eucalyptus species to identify less susceptible plant materials that could be used in areas of high pest incidence. • Methods Feeding damage was assessed in field trials in three consecutive years. No-choice and choice tests were conducted with Eucalyptus species of contrasting susceptibility. • Results Within subgenus Symphyomyrtus, all species from section Maidenaria were used by G. platensis for feeding. Within this section, E. globulus was always the preferred species, while E. nitens was the least preferred. Differences in susceptibility were less pronounced at high attack intensity by G. platensis. Eucalyptus saligna (section Latoangulatae) was the least preferred species among Symphyomyrtus. All species from subgenus Eucalyptus had low susceptibility to G. platensis, particularly E. regnans, which was never attacked under field conditions. The results were confirmed by choice and no-choice laboratory and semi-field tests. • Conclusion Significant differences in susceptibility to G. platensis were found between the 17 Eucalyptus species tested, which could be explored for reforestation with less susceptible plant materials.
... The genus Gonipterus Schoenherr (Coleoptera: Curculionidae: Gonipterini) comprises about 20 Australian species of weevils, all feeding on Eucalyptus leaves (Tooke, 1955;Clarke et al., 1998;Mapondera et al., 2012;Oberprieler et al., 2014). Gonipterus species are oligophagous, feeding on several Eucalyptus species (Newete et al., 2011;Gonçalves et al., in preparations). Three Gonipterus species (G. ...
... as well as other species of the Maidenaria section. Similarly, in field studies in South Africa Newete et al. (2011) recorded feeding and oviposition preferences of Gonipterus sp. 2 (as G. "scutellatus") for E. grandis W. Hill, E. nitens Maiden, E. smithii, E. urophylla S.T. Blake and E. viminalis. Earlier investigations into the host specificity of Gonipterus species in their native range are compromised, because different weevil species (including G. platensis and Gonipterus sp. 2) were lumped into G. scutellatus, even species such as G. notographus that do not belong in the G. scutellatus complex. ...
Article
The study was initiated by the relative failure of the parasitoid Anaphes nitens in controlling the eucalypt weevil Gonipterus platensis on the Iberian Peninsula. Our aim was to gain insight into the community of Gonipterus egg parasitoids occurring in Tasmania. During surveys in 2016 and 2017, adult weevils and egg pods were collected from Eucalyptus trees in Tasmania. The weevils were identified using male genital structure and DNA extracted from hatched larvae. Parasitoids that emerged from the egg pods were identified, and trophic associations of egg parasitoids, weevils and host plants were analyzed. Five species of the Gonipterus scutellatus complex, to which G. platensis belongs, were found, including Gonipterus sp. 2, which is reported for the first time from Tasmania. Molecular analysis corroborated previous phylogenetic studies of this group of species. A sixth species, G. notographus, was also collected. Most species were found to overlap in distribution in Tasmania and, despite being oligophagous, to display selectivity among Eucalyptus species used as hosts: G. platensis and G. pulverulentus were mainly found on E. ovata, Gonipterus sp. 1 on E. nitens and E. globulus and G. notographus on ‘peppermint’ species (E. amygdalina and E. pulchella). Five egg parasitoid species were found associated with these Gonipterus species: Anaphes inexpectatus, A. nitens, A. tasmaniae, Cirrospilus sp. and Euderus sp., with no apparent host specialization. Anaphes nitens, Cirrospilus sp. and Euderus sp. were more frequently found on E. ovata, possibly associated with G. platensis and G. pulverulentus, which were dominant on this host species. Conversely, A. inexpectatus was dominantly found on peppermints (43%), suggesting a main association with G. notographus. Anaphes nitens was found at 23 locations out of 117 and in 2017 was the most abundant parasitoid obtained, with an average 20% parasitism rate, indicating that this species is undergoing a geographical and population expansion since its first report from Tasmania in 2012. These findings contribute to the understanding of the parasitoid-Gonipterus-Eucalyptus trophic relationship and stand to improve future classical biological control programs against G. platensis and other invasive Gonipterus species.
... 22 However, there have been no NIR studies to date on the Gonipterini tribe, which includes a number of species which are economically significant pests of Eucalyptus plantations. [23][24][25] Furthermore, this tribe contains many cryptic species which are difficult to discriminate based on their external appearance. 26,27 Hence chemotaxonomic profiling using rapid techniques such as NIR spectroscopy could be greatly beneficial for discriminating between different species without requiring traditional, dissectionbased morphological methods. ...
Article
This proof-of-concept study aimed to investigate the potential of using near infrared (NIR) spectroscopy to discriminate between genera of Gonipterini weevil. NIR spectra (10,000–4,000 cm ⁻¹ ) were collected from 15 Gonipterini specimens, comprising three genera and five species. Principal component analysis (PCA) highlighted the inter-specific variation in NIR spectra, with separation observed between most species across the first two principal components. Partial least squares discriminant analysis (PLS-DA) could be used to differentiate between the genera (78% accuracy), although support vector machine (SVM) modelling gave improved accuracy (91%). The results support the prospect of NIR spectroscopy for the rapid discrimination between Gonipterini genera.
... It was, therefore, the preferred species to plant around Johannesburg, a city often referred to as the 'city of gold', where to this day several tailings dams with eucalypts trees are still conspicuous on the skyline of the city. This is because of the tree's fast growth rate and its ability to thrive in a wide range of climatic conditions, including soils contaminated with Acid Mine Drainage (AMD), and other metal pollutants (Newete et al., 2011;Carbonnier et al., 2004). ...
Article
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Invasive alien plants are considered as a major threat to many ecological and socioeconomic systems. Nevertheless, the management of some of these plants is often controversial due to the positive socioeconomic and ecosystem roles they play. This necessitates proper mapping and monitoring of the extent and spatial distribution of such plants to prioritize resource allocation and management. However, mapping plant species using remote sensing in a heterogeneous environment such as an urban area is often challenged by high levels of spectral muddle. This study investigated the utility of the high and medium spectral and spatial resolution imageries from the WorldView-2 (WV-2) and SPOT-7 satellites, respectively , to map eucalypts trees in urban areas. Furthermore, the classification performances of Random Forest (RF) and Support Vector Machines (SVM) were compared. Both WV-2 and SPOT-7 imageries attained overall accuracies of 81.67% (0.78 kappa) and 72.78% (0.67 kappa), respectively, when the RF algorithm was used and 80% (0.76 Kappa) and 71.11% (0.65 Kappa), respectively when SVM algorithm was used. The user's accuracies for the eucalypts class in both WV-2 and SPOT 7 imageries were 73.33% and 60%, respectively, for the RF and 70% and 56.67% for the SVM algorithm, respectively. Thus, WV-2 imagery is more suitable for mapping eucalypts trees in a heterogeneous urban environment. Therefore, the classification of WV-2 imageries using RF produced a relatively more accurate map of the eucalypts trees for the study areas, the southern part of Johannesburg city. Ó 2020 National Authority for Remote Sensing and Space Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
... However, under such controlled conditions the impact of the agents can be either under-or over-estimated, as these are not always representative of conditions in the field (Morin et al. 2006(Morin et al. , 2009Rosskopf et al. 1999). For example, the Eucalyptus weevil, Gonipterus ''scutellatus'' Gyllenhal (Curculionidae), was more selective in its feeding and oviposition behaviour on Eucalyptus species in the field in comparison to laboratory trials (Newete et al. 2011) highlighting potential differences in the predicted versus realised host ranges of biocontrol agents. Biocontrol risk assessment generally centres on the dangers of potential non-target feeding of the putative agent (Blossey et al. 2018). ...
Article
Two biocontrol agents, a leaf-spot pathogen, Passalora ageratinae, and a stem gall fly, Procecidochares utilis, have been released against Crofton weed, Ageratina adenophora (syn. Eupatorium adenophorum) (Asteraceae), in South Africa. This work reports the first post-release evaluation of the effect of both agents acting together in the field. A greenhouse trial using both agents had predicted an additive (beneficial) interaction between the agents. This study investigated if the additive interaction was present in the field. Four month old stems were exposed to one of the following three treatments (n = 20 plants per treatment): pathogen-only, pathogen plus single fly-galled, and pathogen plus double fly-galled, for 11 months. The interaction between the agents was equivalent to both agents acting independently (i.e. there was no additive effect on the weed’s growth). The greenhouse trails were therefore not predictive of field conditions.
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Background Gonipterus platensis Marelli (Coleoptera: Curculionidae) is the main defoliating beetle of Eucalyptus L’Hér. (Myrtaceae) plants worldwide. The suitability of Eucalyptus to this pest varies among host plant genotypes. The objective of this study was to evaluate the development, reproduction, and survival of G. platensis on Eucalyptus species and hybrids to assess their suitability to this insect pest in Brazil. Methods The survival, development, and reproduction parameters were evaluated with G. platensis feeding leaves of Eucalyptus camaldulensis Dehnh., Eucalyptus grandis W. Hill., Eucalyptus urophylla S.T. Blake and on the hybrids of E. grandis × E. urophylla ‘H13’ and ‘VR3748’ in the laboratory. Results The duration of the larval stage of G. platensis was shorter on E. urophylla. The pupal stage and the period from larva to adult were equally shorter on E. urophylla and E. camaldulensis . The viability of instars of this insect was low on both E. grandis and E. camaldulensis . The complete lifespan, oviposition period and reproduction parameters of G. platensis were greater on E. urophylla , lower on E. camaldulensis and E. grandis , and intermediate on both hybrids tested. Synthesis Eucalyptus urophylla is the most suitable host for G. platensis survival, development, and reproduction, while E. grandis and E. camaldulensis are the least suitable.
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The Eucalyptus weevil, Gonipterus scutellatus Gyllenhal, is the most serious pest of established Eucalyptus globulus plantations in southwestern Australia where it may have been introduced from its endemic origin in southeastern Australia. This species has been introduced to many countries but has been brought under successful biological control by the introduction of the egg parasitoid, Anaphes nitens Girault, from southeastern Australia. I investigated whether the elevated pest status of G. scutellatus in southwestern Australia is a result of inadequate biological control by quantifying parasitism rates of the pest. Parasitism rates of G. scutellatus egg masses by A. nitens were very low between late winter and mid spring when most oviposition occurs, and a high percentage of parasitised egg masses at these times were incompletely parasitised. Parasitism rates from late spring onwards approached 100%, but fewer egg masses were laid at these times. Low parasitism rates up to mid spring are likely to be due to low numbers of A. nitens at these times because hosts are not available for half the year. In southwestern Australia G. scutellatus has one principal oviposition period in early spring and a second lesser oviposition period in early summer. This short reproductive period appears to be caused by a scarcity of suitable new flushing foliage after spring that is essential for G. scutellatus reproduction. A. nitens did not emerge from eggs of the closely related weevil Oxyops despite eggs of this species being available at a time when G. scutellatus hosts were largely unavailable. Taxonomic difficulties with Gonipterus and possibly Anaphes may also explain the breakdown of biological control in southwestern Australia, and taxonomic revision of these insect groups must be a future research priority.
Article
Gonipterus scutellatus is a significant insect pest of eucalypts in most countries where that genus has been introduced, but is usually only of minor significance in its native Australia. Because of this, much of the research on its biology and host preferences has been done outside Australia. This fact has the potential to produce misleading results as the insect may be forced to choose less preferred hosts, if normally preferred species are unavailable. In part of its native range, in Tasmania, oviposition of G. scutellatus was recorded on seven naturally co-occurring Eucalyptus species that were planted in even aged, replicated plots. Among the seven species were the economically important species, E. globulus and E. viminalis, which have been previously reported as highly preferred hosts. Within plots, oviposition occurred most commonly on three peppermint species (E. pulchella, E. tenuiramis and E. amygdalina) and was rare or absent on the other species (E. globulus, E. viminalis, E. ovata and E. obliqua). Of the peppermints, E. pulchella was the most preferred species for oviposition at this site. A low percentage of peppermints in mixed forest (containing these seven species) immediately adjacent to plots was always matched by low numbers of G. scutellatus eggs within plots; but high percentages of peppermints outside plots could either be matched by high or low numbers of eggs within plots. In the discussion, we suggest that previous studies of G. scutellatus host range may have been limited because the insect was not exposed to hosts it naturally encounters.