Using multiple insecticidal microbial agents against diamondback moth larvae - does it increase toxicity?

ABSTRACT

The use of microbial insect pathogens as biocontrol agents is a well-established practice, with several bacteria and fungi available in commercial products. However, lack of efficacy, persistence and restricted host ranges are limiting the widespread uptake of insect pathogens. Combining multiple agents into a single product may overcome some limitations, if they are compatible and could provide synergy. In laboratory bioassays and field applications, we examined the combined effect of two insecticidal bacteria, Yersinia entomophaga MH96 and Brevibacillus laterosporus (1951 and 1821) and the entomopathogenic fungus, Beauveria bassiana J18 against larvae of diamondback moth, Plutella xylostella. In laboratory bioassays, effects of combined bacterial agents were greater than additive at lower doses, but less than additive at higher dose. Results of the field trial showed no significant difference between the combined agents and the single treatments in most cases, although there was reduction in insect damage in combined treatments.

KEYWORDS:

• Multiple biocontrol agents
• bioassays
• field use
• diamondback moth (DBM)
• entomopathogenic bacteria
• entomopathogenic fungi
• Yersinia entomophaga
• Brevibacillus laterosporus
• Beauveria bassiana

Acknowledgements

The authors would like to thank the Field Service Centre of Lincoln University for their support in preparing the land and for providing the irrigation materials; to AgResearch for the use of the cold room facility and to Dave Saville for statistical advice.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

Original data is available at the Bio-Protection Research Centre, Lincoln University.

Additional information

Funding

This project was funded by Ministry of Business Innovation and Employment grant C10X1310 Next Generation Biopesticides.