NEW ZEALAND - Scientists at AgResearch have found that naturally-occurring bacteria can be used to fight the emerging insect pest known as the plantain moth.
The Scopula rubraria moth is a widespread New Zealand native insect that feeds on a range of plants including plantain.
The relatively recent appearance of this and another similar moth (Epyaxa rosearia) in large numbers in plantain crops has given rise to the commonly used name ‘plantain moth’.
AgResearch Senior Scientist Dr Mark Hurst said that the bacterium Yersinia entomophaga (Ye) could be used as a biopesticide to control at least one plantain moth species, Scopula, populations of which can reach densities of 11,500 larvae per square metre.
Biopesticides are natural pesticides based on micro-organisms. They are targeted as well as safe for the environment and humans and can provide solutions to many insect pest and plant disease problems around the world.
Dr Hurst said that early stage laboratory based research carried out last year during an infestation in the North Island indicated that Ye was an effective tool in killing the Scopula caterpillars.
“Some colleagues investigating the infestation as part of a Beef+Lamb New Zealand project were able to supply caterpillars for an assay and we showed that Ye was very good at killing them.”
Dr Hurst suspects a spray could work effectively and he and colleagues believe that Ye would also be effective against the second species, Epyaxa.
The bacterium will multiply within the dead larvae increasing the persistence and therefore infection rate of the bacterium in the field.
However, spray application of biopesticides is very challenging because the microbes are vulnerable to UV light and drying, both of which cause rapid microbial death.
AgResearch scientist Colin Ferguson said that the caterpillars can be controlled by conventional insecticides, although they are generally broad spectrum, killing beneficial as well as pest insects.
“Consequently, although they have little alternative, farmers are showing increasing reluctance to use such pest control measures.
"Conventional insecticides also have stock withholding periods that need to be observed and that can interfere with grazing management. Biocontrol, or biopesticides, offer an alternative approach to pest control that can alleviate these concerns,” he said.
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