By  NICOLA McCASKILL

European wasp numbers hit a 20-year high in Victoria this summer, prompting calls to resume research and find a scientific solution to control the foreign pests.

Warmer winters and drier summers in recent years have resulted in the worst wasp season for Victoria since the 1990s.

Museum Victoria Entomologist and head of live exhibits Patrick Honan said the wasps were more problematic in Australia and New Zealand than they were in their home territory.

“There’s nothing good to say about them. They’re the only species I feel that way about. But in the Australian environment, they’re not supposed to be here,” he said.

European wasps have no natural predators in Australia and our milder winters mean the nests don't die out in the cold as they do in Europe.

“On average, about 10 per cent of the nests don’t die out … the following spring, they start as a fully-grown nest, and they just get bigger from there,” Mr Honan said.

“If it goes through one season it’s going to be a big nest, but if it happens to go through another season it’s going to be enormous. In Tasmania and New Zealand, nests have been discovered that are the size of a car.”

European wasps are attracted to crops with sweet, soft flesh such as stone fruit and grapes, and are having a continually damaging effect on Australia’s horticultural industry.

“Not only do they damage the fruit themselves, but they can interfere with the processing part of the industry, both by being a danger to workers that are processing the fruits, and also by contaminating the fruits when they’re being processed,” Mr Honan said.

A reduction in insect numbers caused by wasp larvae feeding on insects could have a flow-on effect to other animal populations, he said.

“There have also been cases where birds have been killed in their nests by wasps, and there may also be an impact on competition with other pollinators.”

Despite the significant economic and environmental impacts of European wasps, very little research has been done in Australia on their quantifiable effects on the ecosystem or into potential pest control solutions.

Federal Member for La Trobe Jason Wood is calling for funding to support a research project conducted by the CSIRO into finding a scientific solution to the problem.

Mr Wood brought the issue to the Liberal Party after hearing widespread concern about wasps in his electorate.

“I put it on my Facebook saying, ‘If people think this is an issue, what do you think about trying to get research funding to get a control for it?’ About 200 people shared or made comments on it,” Mr Wood said.

The CSIRO is yet to determine what the actual cost of any prospective research project might be but Mr Wood is optimistic about his chances of securing funding within the May Budget.

“Once we know the figure … we’ll work with the Minister’s office, and obviously the Prime Minister’s office is keen on the issue too,” Mr Wood said.

“If we get the funding for this and get a result, it’d be a huge feather in the cap for Australian scientists, because we’re hearing everywhere in the world that no one’s come up with a solution,” he said.

CSIRO biosecurity research director Dr Andy Sheppard is looking at potential wasp management research and development options but he said they were particularly difficult pests to control.

“Wasps are social insects … by being effective social colonies they can clean themselves  of diseases. They’re adapted to respond to parasites,” he said.

While biological controls such as parasites and bacteria haven’t worked in the past, there hasn’t been enough research to rule it out as an option in the future.

Genetic controls have been considered, however they haven’t been used against a social insect before.

Another option is using micro-sensors to track wasps and locate their nests, technology the CSIRO has previously used to track honeybee movements.

Identifying areas of high nest density, and then safely removing or baiting the nests, is another potential solution.

“Continual efforts need to be made in areas of high wasp density, to try and get the numbers down,” Dr Sheppard said.

“It’s not that nothing can be done, the question is whether or not it’s cost effective.”

Both Mr Honan and Dr Sheppard suggested a better co-ordinated, council-based approach to locating and safely removing nests would be effective, but it would be an ongoing and labour-intensive effort.

Mr Honan also cautioned that commercially available or DIY wasp traps were not as effective as people might think.

“If someone buys a wasp trap, puts it in their garden and they see hundreds of wasps trapped in there, they feel good, but the nests around their house might be producing 100 or 200 new wasps per day. So it’s not going to have a big impact on the overall population,” he said.

Scientific research and development options may take two to five years to implement, but in the meantime something needs to be done to reduce wasp numbers before they reach plague proportions.

“Integrated pest management is not just biological control, it’s chemical control and cultural control … if you use several different control mechanisms, they tend to have a greater impact,” Mr Honan said.

“Next year, if we have a cold winter, then everyone’s going to forget the fact that we have a wasp problem, because there won’t be one next year.

“If we have a mild winter and another dry summer, then the problem’s probably going to come back worse next year. And it will go on like that forever."

Front page image: Juan Emilio/wikicommons