Abstract
The management of pest insects in the field is an ongoing challenge for agriculture. Invasive pest insects’ outbreaks causing increasing damages to local crops are making this challenge even more complex. With world population growth and a shrinking availability of agricultural land through human development and climate change, the need for sustainably enhancing food crop production has never been greater. One strategy to protect food crops is by means of semiochemicals (signal chemicals) to attract or repel insects away from such crops. This will reduce dependency on broad-spectrum eradicant toxic insecticides, which can potentially harm non-target organisms but also rapidly select for resistance. The semiochemicals studied in this dissertation range from yeast volatile organic compounds (VOCs) to terpenes produced through a strategic chemical process using enzymes. The semiochemicals will be analysed and tested on pest insects in two different case studies. The two species taken into consideration are pest representatives for two classes of agricultural crops: fruit crops and viticulture, affected in this case by the spotted wing fly Drosophila suzukii, and cereal crops, affected by the grain aphid Sitobion avenae. Due to the nature of the damage caused by D. suzukii, it is difficult to respect pre-harvest intervals with chemical agents. Therefore, we must rely on a different approach to tackle the problems caused by this pest. We investigated the targeted yeast strains to determine which VOCs they emit. We used techniques like gas chromatography-mass spectrometry (GCMS), solid-phase micro extraction (SPME), behavioural and feeding assays, and electroantennography. We were able to find out that all the yeasts had a distinct volatile profile, and some species increased attraction towards D. suzukii. In the case of S. avenae, the advanced electroantennography technique of single sensillum recording (SSR) allowed us to detect how the aphid antenna responded differently to two sesquiterpenes ((S)-germacrene D and its analogue (S)-14,15- dimethylgermacrene) giving a possible explanation to the different behaviours triggered by the semiochemicals. In both case studies, applications within chemical ecology allow us to modify the insect’s behaviour. We aim to develop new control strategies that will reduce or eliminate the residues of chemical insecticides on fruits, using target volatiles to attract the damaging insects. This would have a significant impact on pest control in agriculture, as it will be effective and safer for the environment at the same time.