- Title
- The host specificity and efficacy of Phenrica guerini (Bechyné) (Coleoptera: Chrysomelidae), a candidate biological control agent of Pereskia aculeata Miller (Cactaceae) in Australia
- Creator
- Dixon, Elizabeth Anne
- ThesisAdvisor
- Paterson, Iain D
- Subject
- Chrysomelidae Australia
- Subject
- Pereskia Australia
- Subject
- Pereskia Biological control Australia
- Subject
- Invasive plants Biological control Australia
- Subject
- Insects as biological pest control agents Australia
- Subject
- Cactus Biological control Australia
- Date
- 2022-04-06
- Type
- Academic theses
- Type
- Master's theses
- Type
- text
- Identifier
- http://hdl.handle.net/10962/290826
- Identifier
- vital:56789
- Description
- Pereskia aculeata Miller (Cactaceae) is a primitive creeping cactus that originated from South America and has become an invasive alien plant in South Africa and Australia. Due to its vine-like growth form mechanical and chemical control are not feasible options for its control, therefore biological control is the best option for controlling this plant. Phenrica guerini (Bechyné) (Chrysomelidae) is a leaf-feeding flea beetle that has been released as a biological control agent against Pe. aculeata in South Africa and has been shown to be damaging at some sites in the country. In this thesis, further studies into the use of Ph. guerini as a biological control agent against Pe. aculeata were conducted to determine whether the beetle should be released as an agent against the target weed in Australia. The host range of a potential biological control agent is important to determine as only monophagous agents, or agents with suitably restricted host ranges, should be considered for release. Host specificity testing was conducted to determine if Ph. guerini was suitably specific for release in Australia. Phenrica guerini larvae only fed and partially developed on three out of 25 test plants, but failed to pupate on any plants besides Pe. aculeata. Adult beetles did not feed on any test plants and only oviposited on one test plant species. Phenrica guerini did not develop on any plant other than the target weed and is therefore suitably host specific for release in Australia. The efficacy of a potential agent is also important to consider as the release of an ineffective agent can reduce the success of a biological control programme. A laboratory based pre-release efficacy assessment was done to determine the impact that Ph. guerini could have on Pe. aculeata. There was a significant difference between the control plants and those with larvae, with an average of 72 (S.E. ± 12.33) less leaves on plants with feeding and the main stem of the plant being 11.1 cm (S.E. ± 7.17) shorter. Although there were no significant differences observed in the number of additional stems, and weights of the different plant parts, this was not a long term study and many of these differences would not have been observed in a short period. Based on the impact observed on the leaves and the main stem, and various field studies that have been done to assess the impact of Ph. guerini on Pe. aculeata in the field in South Africa, Ph. guerini appears to be a potentially damaging agent. As Pe. aculeata is still in its early stages of invasion in Australia the beetle has the potential to be damaging and reduce the invasion trajectory of the plant. This study showed that the beetle is suitably host specific and potentially damaging enough to be recommended for release as a biological control agent against Pe. aculeata in Australia.
- Description
- Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2022
- Format
- computer, online resource, application/pdf, 1 online resource (121 pages), pdf
- Publisher
- Rhodes University, Faculty of Science, Zoology and Entomology
- Language
- English
- Rights
- Dixon, Elizabeth Anne
- Rights
- Use of this resource is governed by the terms and conditions of the Creative Commons "Attribution-NonCommercial-ShareAlike" License (http://creativecommons.org/licenses/by-nc-sa/2.0/)
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | SOURCE1 | DIXON-MSC-TR22-102.pdf | 1 MB | Adobe Acrobat PDF | View Details Download |