Pesticides play an important role in protecting crops against insects, fungi and other pests. However, any new pesticide must also be evaluated for what happens after it has been applied. How long does it remain in the environment? Can it move through soil or water? How is it degraded, and could it affect organisms other than the intended pest?
Peptide based biopesticides represent a promising new generation of crop protection. Peptides are short chains of amino acids, the same building blocks that make up the proteins in all living organisms. Many potentially useful pesticidal peptides originate from compounds produced in nature.
Because peptides can be broken down by naturally occurring enzymes and microorganisms, they may have advantages over compounds that persist for longer periods in the environment. However, we cannot simply assume that this will always be the case for peptide biopesticides. Their degradation may depend on their molecular structure, soil type, temperature, microorganisms and many other environmental conditions. My PhD project investigates what happens to peptide based biopesticides when they enter soil and water. We want to determine how quickly they disappear, whether they bind to soil particles, which processes are responsible for their degradation, and how modifications of the peptide structure influence their environmental fate.
One of the major challenges is simply finding them. Soil and natural water contain thousands of different biological and chemical compounds, while the peptide biopesticide may be present only in extremely small amounts. Detecting a specific peptide biopesticide can therefore resemble looking for a needle in a haystack.
I am developing and comparing different methods for solving this problem. One approach uses antibodies that recognise a specific peptide and may allow us to detect very small quantities. Another uses stable isotope labelling. By following the labelled atoms, we can investigate whether the peptide remains intact, is partly degraded, or is completely broken down.
Combining these methods will help us establish a mass balance showing where the peptide biopesticide goes after it enters an environmental system.
Finally, we will investigate whether exposure to selected peptide biopesticides affects insect behaviour. This will contribute to understanding whether their biological activity is restricted to the intended pest or may also influence other organisms.
Together, these experiments will provide evidence about the environmental behaviour of peptide based biopesticides and support their future development and environmental risk assessment.