By Bob Brown
Thursday 16 Jul 2015
A tiny mite found on wasps continues to look a promising biocontrol agent against the winged pest.
New Zealand’s wasp problem is considered the worst in the world. The pest is estimated to sting the country’s primary industries around $130 million a year. But wasps also pose a hazard to people and harm native bird populations by competing with them for food resources including honeydew and insects.
Landcare Research scientist Dr Bob Brown, who discovered the unnamed mite in 2011, has been researching if they could be a suitable solution. His latest findings suggest they could be.
He has found wasp nests where the mites are present are “significantly smaller”.
“Wasp nests infested with the mites are 50 to 70 percent smaller than uninfested nests,” Brown said.
Another encouraging discovery has been immature mites in wasp nests.
“It’s a good indication that the wasps could be a host for the mites – that the mites presence in the nests is not coincidental,” Brown said.
“Before we started surveying systematically, we only knew that adult mites were found in wasp nests, and we couldn’t say if mites were spending their entire life-cycle in association with wasps or not. Now that we found immature mites in wasp nests we are more confident that the mites are spending a significant part of their life in the nest.
“The relationship between the wasps and the mite is slowly beginning to reveal itself,” he said.
Brown’s earlier research found the mites on sick wasps and those wasps infested with mites did not display normal aggressiveness. Mites were also found on wasp queens hibernating over winter strongly suggesting there was a link between the two organisms from year-to-year.
Landcare Research biocontrol scientist Dr Ronny Groenteman said the new findings were a “great step forward”.
“There is still some way to go though. We still don’t know for certain that the mites adversely affect wasps, that they are safe to other organisms, or that they can be effective – this could take years,” she said.
Brown is currently collecting more information about the mites’ presence on queens over winter and is seeking help from the public. He is after wasp queens from around the country to see how many are infested with the mite.
“At this time of year, the queen leaves the colony to hibernate for the winter. They go in search of somewhere dry and dark. They can often come into people’s garages, sheds or wood piles.
“The queens are distinguishable as they are much larger than workers and, when they are hibernating, can be found sitting quietly with their wings tucked underneath their abdomen.”
Brown said wasp queens were “very docile” when hibernating, but still advised people take care when approaching one. Once captured, he recommended placing the wasp in the freezer overnight to kill it before posting.
Anyone who finds a wasp queen and wants to send it to Brown is asked to post it to PO Box 69040, Lincoln 7640. He recommends putting the dead wasp with tissue paper inside a pill jar. Senders are also asked to include a brief description of where they found the wasp (for example: wood pile), the geographic location and contact details.
Landcare Research has been contracted by the Vespula Biocontrol Action Group to investigate the mite’s potential as a biocontrol agent against wasps.
“We’re delighted with the progress being made by Landcare Research in assessing the impact of the mite on wasp colonies. This could provide enormous benefits to the primary producers and to natural ecosystems. Biocontrol agents are the best long-term solution to dealing with pests on a landscape scale,” Vespula Biocontrol Action Group chairman Bryce Buckland said.
The research is funded by the Ministry of Primary Industries’ Sustainable Farming Fund.