By Ronny Groenteman, Landcare research, Lincoln
Wasps are now widespread throughout New Zealand and in some habitats they are among the most common insects encountered. As a result, wasps have detrimental impacts on native ecosystems, economic impacts on our primary industries, give rise to human health issues, and cause disruption to recreational activities.
Current control options do not provide satisfactory relief, and biological control is thought to be a useful option to explore. When successful, biological control provides long-term, cost-effective solution, covering large scales and difficult terrains. This is especially important when the pest is as widespread as wasps are in natural habitats that are vast and impractical to cover by more intensive control methods.
Biological control against wasps in New Zealand was attempted in the late 1980s, but the first agents to be introduced either failed to establish, or produced insufficient levels of control. Although there were other potential agents to explore, the programme was abruptly discontinued.
At Landcare Research we have recently been thinking that the time was right for re-visiting the programme for biological control of wasps. Not surprisingly then, we were excited to hear about the serendipitous discovery of a seemingly devastating mite in wasp nests in New Zealand.
The mite was discovered by Dr Bob Brown, at the time a PhD student. Bob was working on chemical ecology of wasps, as part of a collaboration between Auckland University and Plant & Food Research at Lincoln. He was seriously upset when some wasp colonies he collected for his study started collapsing in the lab. When he examined the wasps under a microscope, he discovered they were heavily infested with mites. The mites were not easy to identify, and are likely to be a new, yet un-described species. An association between such mites and Vespula wasps has never been recorded anywhere.
Who are these mites? Where have they come from? How long have they been in New Zealand? Are they widespread? Do they actually harm wasps, or are they simply hitching a ride? Can they cause wasps colonies to collapse out in the wild as they seem to have done in the lab? Do they only use wasps as their host, or can they transfer to other insects (honeybees, bumble bees, native bees)? These are only some of the important questions we need to explore in order to determine if these mites can be suitable biocontrol agents against wasps. Luckily now that Bob had completed his PhD on wasp chemical ecology, he no longer views the mites as a nuisance, and is excited about the opportunity to explore their beneficial potential.
To be able to assess the mite as a biocontrol agent, the recently-formed community group V-BAG (Vespula Biocontrol Action Group) will be applying to MPI’s Sustainable Farming Fund in November 2013. V-BAG is based at the Top of the South, and currently includes mainly conservation and restoration volunteer groups, along with Nelson and Central Otago winegrowers. Soon, we hope to see more industries (forestry, apiarists) and more regions represented. Sustainable Farming Fund provides grants for projects of up to thre years, and we hope to get this project funded to commence in the coming financial year (July 2014).