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Improving knowledge of cabbage stem flea beetle biology as a basis for sustainable pest management
Secondary Supervisor(s): Dr Joe Roberts
University of Registration: Harper Adams University
BBSRC Research Themes: Sustainable Agriculture and Food (Plant and Crop Science)
Project Outline
The cabbage stem flea beetle (CSFB) is an economically important pest of oilseed rape (OSR) crops responsible for large economic losses in recent years. These losses have led to the area of OSR grown in the UK declining by 50% over the last 10 years. Development of effective and sustainable solutions for the management of this pest are urgently needed. However, progress has been hindered by a lack of knowledge of the biology of this species. Attempts to develop predictive models to determine when crops are most susceptible to this pest are impacted by a lack of information on the influence of temperature on development and abundance of the life cycle.
1 In addition, farmers widely use cover crops to minimise damage caused by CSFB adults. However, it is not known how CSFB adults respond to plant species used as cover crops and whether these responses are influenced by the volatile organic compounds (VOCs) produced by host and non-host plants. Finally, few studies have previously investigated responses of female and male CSFB to conspecifics and the role of VOCs in mate location.
2 Lack of an effective semiochemical lure, such as a sex pheromone, further limits the ability of farmers to monitor for the presence of this pest.
The aim of this project is to improve management of CSFB through improved understanding of the biology of this species.
Objectives
- Investigate the influence of temperature on development of CSFB life stages, with a particular focus on egg, larval and pupal development.
- Investigate the physiochemical cues that determine the timing of CSFB egg hatch.
- Record behavioural responses of adult CSFB to host and non-host plants, including those species widely used as cover crops by farmers.
- Record the behavioural responses of female and male CSFB adults associated with mating.
- Identify VOCs associated with behavioural responses to host/non-host plants and conspecifics.
Methods
The influence of temperature on CSFB development (O1) will be investigated under laboratory conditions using constant and fluctuating temperatures. Methods previously used3 will be further developed. Each developmental stage of the CSFB life cycle will be studied: eggs, larvae, pupae and adults (including pre-reproductive, productively active and post reproductive) and thermal requirements calculated.
Physiochemical cues determining timing of egg hatch (O2) will be investigated by recording egg hatch in the field alongside detailed measurements of soil conditions (temperature and moisture content), presence of root exudates (analysis through HPLC) and microbes (analysis through eDNA). Field work will be complemented with laboratory experiments that will investigate these physiochemical cues in isolation and in combination.
Behavioural responses of adult CSFB (O3 & O4) will be recorded using olfactometer experiments, drawing on best practice for this approach.4 Specifically, state-of-the-art four-armed olfactometers will be used to assess the responses of female and male CSFB to OSR, cover crop (e.g. fenugreek) and conspecifics. Movement of beetles within olfactometers will be recorded using an Ethovision XT system to record time spent within the zones of the arena corresponding to each odour.
Identification of VOCs associated with behavioural responses of CSFB adults (O5) will be done through use of air entrainments where volatiles associated with OSR, cover crops and conspecifics will be trapped on Porapak filters. Trapped volatiles will be eluted and analysed using gas chromatography and mass spectrometry. Activity of VOCs identified will be investigated using the olfactometer system described above.
References
1. Ewing, D.A. et al. (2024) Temperature and time of season are the predominant drivers of cabbage stem flea beetle, Psylliodes chrysocephala, arrival at oilseed rape crops. Crop Prot. 185: 106904.
2. Peng, C. & Weiss, M.J. (1992) Evidence of an aggregation pheromone in the flea beetle,Phyllotreta cruciferae (Goeze) (Coleoptera: Chrysomelidae). J. Chem. Ecol. 18: 875-884.
3. Mathiasen, H. et al. (2015) Effect of temperature on reproduction and embryonic development of the cabbage stem flea beetle, Psylliodes chrysocephala L., (Coleoptera: Chrysomelidae). J. Appl. Entomol. 139: 600-608.
4. Roberts, J.M. et al. (2023) Scents and sensibility: Best practice in insect olfactometer bioassays. Ent. Exp. Appl. 171:808-820.
