Inside her government laboratory in southwestern Ontario, entomologist Tara Gariepy is on the hunt for a killer smaller than a pinhead.
Her mission is to find minuscule insects that will lay eggs on the crop-destroying brown marmorated stink bug and feed on the pest’s fluids and organs until it dies. Undetected in North America until 13 years ago, the stink bug has spread rapidly through the United States, ravaging everything from apples and peaches to lima beans and corn.
The invasive pest is expected to swarm Ontario soon and could deliver a big economic blow to the agriculture industry. The bug was found in the field for the first time this past summer in a backyard vegetable garden in Hamilton. It won’t be long before the stink bug hits the farm.
In this race against time, Dr. Gariepy is deploying molecular diagnostic tools to fast-track an age-old process known as biological control. Through extracting and analyzing bug DNA, she can identify invasive pests and their range within 24 hours instead of weeks, accelerating the search for a natural enemy.
“We are trying to intercept things a lot quicker,” said Dr. Gariepy, who began work at Agriculture and Agri-Food Canada’s research centre in London, Ont., in January.
“Part of the problem in the U.S. was that the brown marmorated stink bug was likely there for a couple of years and because they weren’t expecting it, they weren’t looking for it. And by the time they actually saw it, it had already reached epidemic proportions.”
Invasive insects and plants are a costly problem in agriculture and forestry. The federal government estimates the industries lose a combined $7.5-billion in revenue each year due to damage caused by pests.
Increased travel and global trade have brought an unprecedented number of invasive species to Canada. At the same time, more and more insects are becoming resistant to pesticides, a problem that has prompted governments and food producers to look increasingly to nature – and biological control – for solutions.
With the introduction of a national pesticide risk reduction program in 2003, biological control has gained research steam. Dr. Gariepy is part of a team of federal scientists focused on finding insects, plants and other natural enemies to thwart the spread of invasive pests and save vital food crops.
At her high-tech lab in London, pairing DNA analysis with computer databases allows Dr. Gariepy to identify insects much more quickly than with older techniques. Molecular tools also allow her to examine insects before they mature. Eggs alone are enough to determine whether a destructive pest is present in crops, which wasn’t possible before.
While biological control can greatly reduce reliance on chemical sprays, it has its drawbacks. For food producers, it’s laborious and it’s not a quick fix.
“They love the concept, but it’s more difficult than the pesticide-spray program to put into practice,” noted Bruce Broadbent, a federal research scientist with the biological control team. “It takes a lot more hand holding and capacity building.”
Biological control can have unintended consequences, too.
When a parasitic fly from Europe was released to reduce the gypsy moth population in northeastern United States, the insect killed huge numbers of wild silk moths, a University of Massachusetts-led study found in 2000. The research offered some of the first compelling evidence of the risks associated with introducing foreign species.
The controlled environment of greenhouses is a major reason biological control remains more popular in hothouse agriculture than in farm fields.
At John Wise’s mixed farm northeast of Napanee, the tarnished plant bug has been causing trouble for more than a decade. The insect is a major problem for Ontario strawberry growers. It sucks the sap out of berries, leaving them “cat faced” and unmarketable.
One year, the pest destroyed three-quarters of Mr. Wise’s strawberry crop. The 61-year-old organic grower was eager to give the government’s biological-control strategy a try.
Hundreds of tiny wasps from Europe, barely visible to the naked eye, were released on several farms in Southern and Eastern Ontario in 2007 and 2008. Alfalfa, a preferred food source of the pest, was also planted next to strawberry fields to lure and trap it.
It’s too soon to tell whether the natural enemy will significantly reduce the pest’s population. Scientists hope the wasp’s population will increase on its own and kill off a great number of tarnished plant bugs.
“To reduce populations of a pest takes many seasons,” Dr. Broadbent said. “I always have to emphasize biological control is a long-term solution.”
With the brown marmorated stink bug, scientists are working to devise a biological-control strategy before the insect’s population gets out of hand in Canada. At her lab last week, Dr. Gariepy matched tiny parasitic wasps with stink-bug eggs to see if the wasps would attack.
The experiment involved different stink bugs than the brown marmorated variety. She plans to use molecular techniques such as DNA barcoding to create genetic profiles of parasitoids collected from across Canada.
The profiles will allow scientists to test biocontrol agents. It’s all part of the hunt for the most potent natural enemy.
