Ontario scientists are using caterpillars to combat an invasive aquatic plant
In cities including Hamilton, Windsor and North Bay, scientists are releasing caterpillars that eat reeds
Ian Jones wades through a forest of aquatic plants, his feet sinking into the muddy ground. He's surrounded by invasive phragmites, a reed that can grow five metres high and whose roots release biochemicals impeding the growth of other plants.
In this particular patch of land, near the Binbrook conservation area in southeast Hamilton, the phragmites haven't fully taken over. But in many parts of Ontario, the reed has out-competed and replaced native species in previously diverse environments.
Jones is here on a mission. If he and his team are successful, sites like this may yet resist the invasion.
Weaving between stems, he crouches down by a canister staked about knee high off the ground. Opening the lid, he reveals his team's secret weapon: multiple tiny caterpillars.
Since 2021, Jones's team has released over 21,000 caterpillars and larvae at around 30 locations across Ontario such as this. The Canadian Food Inspection Agency (CFIA) approved two moth species, Lenisa geminipuncta and Archanara neurica, for use as biocontrol in 2019. The caterpillars only eat phragmites, Jones said, and as they grow, they'll "hopefully" munch through three or four stems and "do a fair amount of damage to the phragmites."
"This biological control is hopefully something that will be longer term and sustainable," Jones told CBC Hamilton.
In most cases they've seen, he said, the insects damage nearby phragmites. In all cases where they've done damage within a year, the moths return the year following.
"We know they're reproducing successfully in Canada and they're overwintering successfully, which are both big steps to make in the early stages of a biological control program."
The scientist is working with Ducks Unlimited Canada, the federal department of Agriculture and Agri-Food Canada, the University of Toronto, and the Centre for Agriculture and Bioscience International in Switzerland.
In addition to canisters, Jones and his colleagues release caterpillars from cut phragmites stems they secure in florist foam blocks and leave on the ground.
Jones said the caterpillars have been used in other countries, but it took about a decade for their potential impacts to be studied and approved in Canada. That research shows that the moths should only impact phragmites, he said.
"We were very comfortable to start releasing them in Canada."
The work in Ontario extends from Windsor in the southwest, to North Bay, to east of Ottawa. Ducks Unlimited Canada helped select the sites based on a number of criteria including geographic distribution, the organization's Ontario invasive species lead Matt Bolding said.
"The best way to utilize the tool is to know where to use it."
Scientists hope to learn more about where the moths are most effective and use that to maximize their effectiveness.
"Here in Ontario and out east, phragmites probably represents the biggest threat from an invasive plant, mostly because it is so well established, particularly in southern Ontario," Bolding said.
And invasive species, he added, are a top threat to wetlands.
According to Ontario's Invasive Species Centre, the invasive kind of phragmites — which is regulated under the province's Invasive Species Act — is a poor source of habitat and food for native wildlife like turtles, can cause lower water levels, and impact swimming, boating and fishing.
When out in nature, the centre advises staying on designated trails and cleaning off clothing and equipment to avoid tracking phragmites seeds to other places.
"What we would hope over the next four or five years is that we start to see noticeable reductions in the voracity of the phragmites," Jones said.
"We'll see reductions in stem density and stem height, reductions in flower formation and ultimately that we start to see other native plants regain a foothold in those infested sites."
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