FAR's discovery of a previously unknown predator of one of New Zealand’s most costly agricultural pests has scientists puzzled.
The story began in November last year when FAR staff collecting grass grub pupae for a grass grub feeding project found pupae being eaten alive in the soil by unknown maggot-like larvae.
FAR Research Manager Richard Chynoweth says at first they couldn’t quite believe what they were seeing.
“Grass grub is one of New Zealand’s most costly, and therefore most researched pest insects, but we had no knowledge of this sort of predation occurring.”
The team gathered as many of the larvae as they could and drew together an expert team from across New Zealand and the world in order to lean more. Several months of laboratory rearing, DNA testing and combing the scientific literature ensued, and the group learned that they had indeed, found something new.
“We discovered that the larvae were Ostenia robusta, a native, but not well recorded carnivorous fly. Larvae of this fly had never been found and studied before, although adult flies were in several New Zealand museum insect collections. They had also never been recorded as having any sort of association with grass grub, another native species.
“Since then we have been looking for more O. robusta across Canterbury, but have only found more larvae, which have yet to be positively identified as the same species. We placed a number of fly traps across mid and central Canterbury last summer but unfortunately didn’t catch any adult flies. We will try again this summer placing the traps at different heights.
“Our main aim for this project now is to learn more about the distribution and the biology of this insect and to confirm that this finding wasn’t just a one-off. Once we have more information about O. robusta we can start to make decisions about whether or not is has potential for use within integrated pest management systems.
This work was presented to the wide science community at the New Zealand Plant Protection Society in Napier in August.
FAR discovers new grass grub predator
