- Title
- Pre-release evaluation of stem-galling and seed-feeding midges (Diptera: Cecidomyiidae) from South Africa as biological control agents for Guinea grass (Megathyrsus maximus) in Texas, United States
- Creator
- De la Fontaine, Benjamin
- Subject
- Guinea grass Biological control Texas
- Subject
- Gall midges
- Subject
- Invasive plants Biological control Texas
- Subject
- Maxent
- Subject
- Phylogeny
- Subject
- Grasses Texas
- Date Issued
- 2025-04-02
- Date
- 2025-04-02
- Type
- Academic theses
- Type
- Master's theses
- Type
- text
- Identifier
- http://hdl.handle.net/10962/479002
- Identifier
- vital:78248
- Description
- Guinea grass (Megathyrsus maximus) is a tall-statured C4 grass with a native range spanning sub-Saharan Africa. Intentionally exported for centuries for its grazing value, it has become a near-global invasive. Texas, USA is the first territory to initiate a biological control program for Guinea grass, targeting an invasive population with genetic origins that have been traced to South Africa. This study focuses on the identification and evaluation of biological control agents for Guinea grass. Native-range natural enemy surveys were performed in South Africa, resulting in the identification of several undescribed species of phytophagous midges (Diptera: Cecidomyiidae) on Guinea grass, including stem-galling taxa (gall midges) and seed-feeding taxa (seed midges). These taxa are expected to be highly host-specific based on the known biology of this family of insects, but the difficulty of rearing them in the laboratory necessitated field-based assessments. Field host range assessments of stem gall midges resulted in the rejection of one candidate (the horn gall midge, undescribed sp.) due to feeding on a relative of the target plant, Batochloa deusta, and the prioritization of another candidate (the blister gall midge, Arabukodiplosis vesicaria) that feeds only on Megathyrsus maximus. Combined field host range evaluations and phylogenetic analysis of a cryptic species complex of seed midges resolved this as a new genus containing up to seven species, with five species that are likely to be specific to their respective Panicoideae grass hosts, including Megathyrsus maximus and Cenchrus ciliaris (buffelgrass – also invasive in the USA). Climate matching models for the blister gall midge and seed midge on Guinea grass predicted high likelihood of establishment and nearly complete coverage of invaded sites in Texas, and identified northern KwaZulu-Natal, South Africa as an ideal source region for Guinea grass biocontrol agents. The nascent sub-field of grass biocontrol research has developed slowly because of inaccurate perceptions that grasses lack host-specific herbivores, and faces a severe taxonomic impediment given the large number of undescribed insect species feeding on grasses, especially in Africa. This study has contributed to resolving both challenges by identifying several new host-specific insect species, showing that the prospects for future success and discovery in grass biological control are promising.
- Description
- Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2025
- Format
- computer
- Format
- online resource
- Format
- application/pdf
- Format
- 1 online resource (169 pages)
- Format
- Publisher
- Rhodes University
- Publisher
- Faculty of Science, Zoology and Entomology
- Language
- English
- Rights
- De la Fontaine, Benjamin
- 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 | DE LA FONTAINE-MSC-TR25-30.pdf | 2 MB | Adobe Acrobat PDF | View Details Download |