The diamondback moth (DBM), Plutella xylostella L. (Lepidoptera: Plutellidae), is the most important global pest of Brassica crops. It is now prevalent wherever Brassicas are grown and costs the agricultural industry US$ 4-5 billion annually. Traditionally, DBM is controlled by the use of insecticide only applications which has led to wide spread insecticide resistance in DBM populations. As insecticide only control strategies are not viable in the long term, it is the opinion of many experts that integrated pest management (IPM) is the way forward for DBM control. A component of the IPM system which holds great potential is entomopathogenic fungi (EPF). Despite their promise, EPF are not currently routinely used by growers to control DBM. This is mainly because the efficacy of EPF biopesticides tends to vary from one application to the next. The aim of this project was to study interactions between EPF and other elements of the IPM system to understand and address sources of variability. Temperature is the most important determinant of EPF growth, virulence and DBM development. However, there are considerable knowledge gaps when it comes to understanding the effect of temperature on these processes. This is mainly because of the left-skewed nature of the physiological response to temperature. We assessed the suitability of five non-linear models to describe these interactions and found Briere-1 to be the most appropriate model. Cardinal temperatures taken from it were used to develop a day-degree (DD) model which could accurately predict the virulence of EPF against DBM at fluctuating, “field realistic”, temperatures. In an IPM system, EPF would be applied with synthetic insecticides. Consequently, it is important to know how co-application of these products would affect the survival of groups of DBM larvae. After applying low-concentrations of various insecticides with EPF we found there to be negligible evidence of antagonism, indicating the insecticides and EPF are compatible for use within an IPM system. Finally, the effect of the age structure of the DBM larval population on efficacy of EPF biopesticides was investigated. We found that, because larvae slough off conidia during ecdysis, time between treatment of EPF and moult had a significant effect on larval mortality. It is hoped that this study will improve growers’ confidence in EPF biopesticides, and expedite their use within IPM systems to control DBM.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:742258 |
| Date | January 2017 |
| Creators | Perry, Declan Joseph |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/102817/ |
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