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

This project will provide new knowledge on combining host plant resistance and fungal biopesticides for management of the diamondback moth, (DBM) Plutella xylostella. There is a need for new, safe DBM treatments based around Integrated Pest Management, in which different crop protection practices are combined in complementary ways. Partial resistance to DBM is reported in different Brassica species, is likely to be durable, and it could form the centrepiece of an IPM system. Biocontrol with natural enemies is particularly important for DBM given its propensity to develop pesticide resistance. Biopesticides based on entomopathogenic fungi (EPF) are useful here because they can be applied with conventional spray equipment. A challenge with EPF is that larvae can 'escape' infection by moulting. Our hypothesis is that partial resistance that slows down DBM development will enhance EPF efficacy by giving more time for spore infection.
Brassica accessions (including lines from a diversity fixed foundation set) will be screened for resistance, recording larval survival, adult emergence time, and plant damage. Promising accessions will be selected for more detailed studies to quantify DBM instar development rates and fecundity of emergent adults. Laboratory bioassays will be used to quantify the effects of EPF strains on the survival, longevity, food consumption and fecundity of different life stages of DBM. A track sprayer will be used to optimise spray conditions (water volume, pressure, forward speed) using the effective dose of leading EPF strains as a reference point. Experiments will then be done to quantify effect of combining EPF with 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, synergistic, or potentiation) will be determined by comparing predicted and observed values for DBM mortality.