Host-specificity testing of the leaf-feeding flea beetle, Phenrica guerini, a biological control agent for the invasive alien cactus, Pereskia aculeata
- Authors: Dixon, Elizabeth , Paterson, Iain D , Muskett, Phillippa C , McConnachie, Andrew
- Date: 2023
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417687 , vital:71478 , xlink:href="https://doi.org/10.1080/09583157.2023.2214342"
- Description: Pereskia aculeata Miller (Cactaceae) is an environmentally damaging invasive alien plant in South Africa and Australia. The flea-beetle, Phenrica guerini Bechyné (Coleoptera: Chrysomelidae), has been used in South Africa as a biological control agent against the plant for more than 30 years but updated host-specificity testing was required to determine its suitability as an agent in Australia. No-choice larval survival tests were conducted on 26 test plant species from 11 families, with survival to the adult stage only being recorded on the target weed, P. aculeata. No-choice oviposition testing with adult P. guerini was conducted on six test plant species. No adult feeding was recorded on any test plants and significantly more eggs were oviposited on P. aculeata (158.8 SE ± 21.4) than on Talinum caffrum (5.2 SE ± 5.2), which was the only test plant on which they oviposited. The adults survived on average 27 days longer on P. aculeata than on any test plant species. In a multiple-choice trial that included all three species that supported any larval feeding as well as P. aculeata, oviposition and feeding was only recorded on target weed. Phenrica guerini is suitably host specific for consideration in Australia as a biological control agent against P. aculeata.
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- Date Issued: 2023
Biological control of cactaceae in South Africa
- Authors: Paterson, Iain D , Klein, Hildegard , Muskett, Phillippa C , Griffith, Tamzin C , Mayonde, Samalesu , Mofokeng, Kedibone , Mnqeta, Zezethu , Venter, Nic
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/${Handle} , vital:71034 , xlink:href="https://hdl.handle.net/10520/ejc-ento_v29_n3_a4"
- Description: Cactaceae are among the most problematic invasive alien plants in South Africa, posing serious negative consequences to agriculture and natural ecosystems. Fortunately, South Africa has a long and successful history of controlling cactus weeds using biological control (biocontrol). This paper reviews all the biocontrol programmes against invasive alien Cactaceae in South Africa, focusing on the decade since the last review published in 2011, up to, and including 2020. Biocontrol programmes against 16 target weeds are summarised, all of which rely on either the galling mealybug, Hypogeococcus sp. (Pseudococcidae), or various species or intraspecific lineages of cochineal insects (Dactylopius spp., Dactylopiidae) as agents. New agents are being considered for the three target weed species, Opuntia elata Salm-Dyck, Opuntia megapotamica Arechav. and Trichocereus spachianus (Lem.) Riccob., while permission to release a new agent against Cylindropuntia pallida (Rose) F.M. Knuth has recently been granted. The biocontrol agent, Dactylopius opuntiae (Cockrell) ‘stricta’, which has been utilised for the successful control of Opuntia stricta Haw., has shown some promise as an agent against one of the worst cactus weeds in the country, the North Cape/Free State variety of Opuntia engelmannii Salm-Dyck. Post-release monitoring and recent observations of the status of control for the 11 other cactus weeds, all of which have well-established agents, are provided. Taxonomic uncertainties and misidentifications of both target weeds and agents has been a constraint to biocontrol efforts, but this has been partially overcome through the use of genetic techniques. Biocontrol is particularly successful in controlling cactus weeds compared to most other taxonomic groups, and it is likely that past successes can be repeated with new target weeds. Mass-rearing and redistribution of agents are essential to gain the maximum possible benefit from cactus biocontrol agents, and recent increases in mass-rearing outputs have been beneficial.
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- Date Issued: 2021
Ground-truthing climate-matching predictions in a post-release evaluation
- Authors: Muskett, Phillippa C , Paterson, Iain D , Coetzee, Julie A
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423504 , vital:72067 , xlink:href="https://doi.org/10.1016/j.biocontrol.2020.104217"
- Description: Pereskia aculeata Miller (Cactaceae) is an invasive alien cactus which has negative impacts on indigenous plant biodiversity in South Africa. Catorhintha schaffneri Barilovsky and Garcia (Coreidae), the pereskia stem-wilter, was collected at coastal sites in the subtropical region of Santa Catarina state in southern Brazil and released as a biological control agent to control P. aculeata, in South Africa, in 2014. The introduced distribution of P. aculeata covers a wide variety of climatic conditions which was expected to influence the establishment success of the new agent. The thermal tolerance of C. schaffneri was investigated by developing a degree-day model and calculating the thermal limits of the species. The influence of humidity on egg hatchability and adult survival was also investigated. These data were then used to determine where the agent was likely to establish in South Africa using both weather station and microclimate temperature data. To ground-truth these predictions, sixteen release sites were selected covering a wide range of climatic conditions in the introduced distribution. Three releases of 30 adult C. schaffneri were conducted at each site and population establishment was recorded. Field establishment was recorded at only two of the sixteen experimental release sites. Low winter temperatures were predicted to prevent establishment at seven of the sixteen sites, but nine sites were considered climatically suitable according to the agent’s thermal physiology. Low rainfall and humidity could explain why the agent did not survive at some sites with suitable thermal climates. Many of the thermally suitable sites were affected by a severe drought over the course of the experiment, so further releases during periods with average rainfall and humidity are warranted and could confirm whether the drought was a significant factor influencing the failure of the agent to establish. Although climatic-matching and thermal physiology studies are valuable for tentative predictions of establishment success, there are numerous variables involved that require ground-truthing. Releasing the agent over a wide range of climatic zones believed to be within the thermal limits of the agent, and following releases with detailed post-release evaluations may be the best method of determining where future releases should be focused.
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- Date Issued: 2020
Pereskiophaga brasiliensis, a natural enemy of the invasive alien cactus Pereskia aculeata, is not suitably host specific for biological control in South Africa
- Authors: Paterson, Iain D , Muskett, Phillippa C , Mdodana, LL , Vitorino, Marcello D
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417498 , vital:71458 , xlink:href="https://doi.org/10.1080/09583157.2019.1581132"
- Description: The stem-mining weevil, Pereskiophaga brasiliensis, was a candidate biological control agent for the invasive cactus Pereskia aculeata in South Africa. In host specificity trials, it developed on two indigenous test plant species under choice and no-choice conditions. Pereskiophaga brasiliensis is therefore not suitably host specific for release in South Africa.
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- Date Issued: 2019
Macroinvertebrate communities associated with duckweed (Lemnaceae) in two Eastern Cape rivers, South Africa
- Authors: Muskett, Phillippa C , Hill, Jaclyn M , Weyl, Philip S R
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444065 , vital:74182 , https://doi.org/10.2989/16085914.2016.1241173
- Description: The functional feeding groups and diversity of macroinvertebrate communities associated with duckweed mats in the New Years River (two sites) and Bloukrans River (two sites), Eastern Cape province, South Africa, were assessed. Duckweed (Lemnaceae) is a ubiquitous family of floating macrophytes. A total of 41 macroinvertebrate families were collected monthly over a six-month period from February to July 2014. Duckweed biomass in both rivers was highly variable both temporally and spatially. The majority of identified macroinvertebrate taxa were predators and detritivores, with a small percentage of herbivores. An average of approximately 26% of the macroinvertebrate taxa found were from families that include species from more than one functional feeding group. Although overall measures of diversity and ecosystem health (Fisher’s α and Simpson’s index) remained constant over time in the New Years River, significant differences in macroinvertebrate community structure were seen between sites and months on both rivers, with dissimilarity being driven by a larger number of species in the New Years River. This high variability within macroinvertebrate assemblages probably reflects a combination of heterogeneous duckweed distribution, variation in physico-chemistry, opportunistic behaviours of macroinvertebrate predators and/or successional colonisation of duckweed mats.
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- Date Issued: 2016