Scientists in Great Britain learn about parasitic wasp by accident while collecting beetles for a feeding preference trial
By sheer chance, researchers at the John Innes Centre at Norwich in the United Kingdom have discovered a wasp that lays its eggs inside the body of cabbage stem flea beetles. Once the larvae have emerged after passing through the digestive system, the beetles are rendered sterile and die.
The discovery was made when the research team found the wasps in colonies of the beetles that were being studied to test their feeding preferences on canola. The beetle is a major threat to canola, causing extensive damage known as “shot-holing” to leaves that leads to crop failure or poor yield.
Read Also
Trade war may create Canadian economic opportunities
Canada’s current tariff woes could open chances for long-term economic growth and a stronger Canadian economy, consultant says — It’s happened before.
“We started rearing beetles around 2012, 2013,” said Dr. Rachel Wells, senior scientist and project manager.
“We knew there were beetles coming into the fields as this (region in Norwich) was a hot spot area. For some of the work we required large amounts of beetles, so we collected them and kept them in the control bags. Then we started noticing that we were getting wasps in these contained colonies. We had never seen anything like it before. There were these small wasps in the bags.”
The research team had collected about 3,000 beetles from three sites around Norfolk and the beetles had been infected by wasps. Following genetic sequencing by the Natural History Museum in the U.K. and the Swedish Museum of Natural History, the wasp was identified as an obscure species called Microctonus brassicae, first reported in 2008 but not identified again until recently. Wells said that they were really surprised by the discovery of the wasp and they had no idea that they were out in the crop fields in such numbers.
“It was a really, very lucky find,” she said. “But it was also unlucky for us because the wasps took out our captive colonies for research. But the wasps opened up this whole other avenue of research and the possibility of using parasitoid wasps as bio-controls for farmers and growers of oilseed rape and brassica vegetables as part of an integrated pest management approach.”
The cabbage stem flea beetle is a serious pest in the U.K., especially in eastern regions since the European ban on the use of neonicotinoid seed treatment on flowering crops.
In Canada, eight flea beetle species attack canola and mustard, according to the Canola Council of Canada.
Work is ongoing by Wells’s team to find out what the parasitism rate is in the field and whether it is lower than what they have learned about the wasp in captivity. Wells said the study showed that the wasp’s rate of parasitism in the lab was greater than 44 percent.
The study has raised the possibility of using the wasp and other species that are genetically similar to parasitic wasps as a form of bio-control to protect canola and other commercially important crops vulnerable to attack from the destructive beetle, despite the fact that past bio-controls have had limited effectiveness.
“I think the thing is that, until recently, we have controlled the beetles using chemicals so nobody has been studying them, nobody has been out there looking at the interaction between the beetle and the wasp,” she said. “But when you are no longer reliant on chemical control and you are out in the field studying them, you will probably notice many more parasitoid situations affecting the life cycle. I am working in plant genetics, looking at the genetics of resistance and seeing if we can breed something of more resistance.”
She said that the next step is to see how widespread these wasps are and what is the actual parasitism rate in the field. But she pointed out that there are a lot of steps to turning this into a commercial venture.
The study is the first English published description of the parasitoid of the adult cabbage stem flea beetle and it was published in the journal Entomologia Experimentalis et Applicata.
