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Developing a sustainable management system for the diamondback moth, a globally important crop pest

Primary Supervisor: Dr Dave Chandler, School of Life Sciences

Secondary supervisor: Dr Graham Teakle

PhD project title: Developing a sustainable management system for the diamondback moth, a globally important crop pest

University of Registration: University of Warwick

Project outline:

The diamondback moth (DBM) Plutella xylostella is a brassica-feeding specialist and one of the most important pests worldwide, causing US$5 billion crop losses globally p.a. DBM has evolved resistance to most of the available chemical pesticides used against it. This is causing major problems, particularly in developing countries where, in addition to crop losses, smallholder farmers - normally with inadequate PPE - are forced to use ever more frequent applications of toxicant pesticides with their associated health risks. Therefore, there is an urgent need for new DBM treatments and sustainable systems for using them. Most experts see Integrated Pest Management (IPM) as the way forward. IPM is a systems approach that combines different crop protection practices with careful monitoring of pests and natural enemies. Biocontrol with natural enemies is particularly important for DBM given its propensity to develop pesticide resistance. Sustainable pest management will need to be based on integrating different crop protection methods rather than relying in a single ‘silver bullet’ approach. However, there is currently a poor understanding of how different crop protection tools interact.

In previous research, we have identified the components for a new, safe, biologically-based IPM system of DBM, including candidate Brassica accessions with partial resistance to DBM larvae (taken from a fixed foundation diversity set), and strains of insect pathogenic fungi (Beauveria bassiana and Metarhizium spp.) that can be used as biocontrol agents. The aim of this is to provide new knowledge on the interaction between these two control options. Our IPM strategy is to use partial varietal resistance to slow down DBM developmental while at the same time enhancing the performance of biocontrol agents. Slower DBM development increases the time for which they are susceptible to entomopathogen infection (e.g. by preventing young instars ‘escaping’ from fungal spores by moulting). An added benefit is that partial resistance will be under a much lower selection pressure than major gene resistance and should prove more durable.

The outline plan for the research is as follows:

  • We will carry out a bioinformatics analysis of RNASeq data from Brassica accessions known to show variation in their susceptibility to DBM larvae. The emphasis will be looking for correlations between resistance / susceptibility and variation in expression of signalling pathways associated with insect defence including JA signalling, phytoalexin (including camalexin) synthesis and glucosinolates. This will include an analysis of variation in expression of Brassica orthologues of genes associated with DBM resistance in Arabidopsis. The data could be used to provide markers for subsequent crop genetic improvement studies.
  • Promising Brassica accessions (up to 20) will be validated by rt-PCR and then bioassayed in an infestation study using a DBM culture to quantify larval survival, rate of development, and longevity and fecundity of emergent adults.
  • Laboratory bioassays will be used to quantify the effects of selected strains of entomopathogenic fungi (Beauveria bassiana, Metarhizium brunneum) on the survival, longevity and fecundity of different life stages of DBM on contrasting susceptible vs. partially resistant Brassica lines. We hypothesize that the partially resistant plants will result in increased DBM mortality and lower adult reproduction. The nature of the effect (additive effect, synergistic interaction or potentiation) will be determined by comparing predicted and observed values for DBM mortality.
  • Semi-field (cage) experiments will then be done to investigate an IPM system combining durable, partial crop resistance with selected Brassica lines, and fungal biopesticide sprays. The aim here is to use information from the laboratory work to optimise the timing and frequency of spray applications for maximum effect.

BBSRC Strategic Research Priority: Sustainable Agriculture and Food: Plant and Crop Science

Techniques that will be undertaken during the project:

  • Bioinformatics
  • Quantification and analysis of gene expression
  • PCR
  • Insect rearing
  • Mycology and production of entomopathogenic fungi
  • Laboratory dose response bioassays of insect pathogens
  • Statistical analysis and modelling (survival analysis, dose response analysis)

Typical pattern of working hours:

  • 37.5 hrs per week with flexible working arrangements

Contact: Dr Dave Chandler, University of Warwick