P.E.I. research digs into wireworm behaviour to help fight costly pest 

A research scientist on P.E.I. is studying the behaviour of the wireworm in the hopes of helping stop what an Island potato farmer calls "one tough pest."

In her latest research, Christine Noronha is looking at how the wireworm moves through soil to search for food, and how long they can survive freezing temperatures. 

"We didn't know what wireworms were doing in the soil because they're underground. You don't see them. You don't know how they're moving," said Noronha, a research scientist with Agriculture and Agri-Food Canada.

"Unless you know where they move and how far they move, it's very difficult to use control techniques and to find out how many wireworms you have in your field."

'They move pretty far'

Noronha said a couple of her studies have found the wireworms move quickly through the soil. 

"We found that they can move up to 3.6 metres in about 24 to 48 hours. They're moving pretty fast in the soil horizontally," Noronha said.

"That's what happens in the summer when they're moving from plant to plant, and trying to to find food. So we know that they move pretty far."

Noronha said another trial looked at what the wireworms did in the fall and into the winter, as they go into diapause, which is an insect's version of hibernation.  

"Because in the fall, they will eat a lot of food. They'll destroy your crops, especially root crops like potatoes, rutabagas, carrots, because they're feeding to go into into diapause," Noronha said.

"We wanted to know when do they go down into the soil, and when do they come up? And it was mainly because we wanted to know when do we put our baits in the field to figure out what the population is."

Noronha and her team put tubes into the ground, about 80 centimetres down, with temperature monitors at different depths.  

She said the wireworms start moving down in the soil in November, and then, mainly in April, start to move back up again. 

"What we found was the best time to put your baits out in the field to see how what your population is, is around mid-May. That's the best time," Noronha said. 

Freezing point

Noronha said they also did trials to see at what temperature the wireworm freeze.  

"We put the temperature down to -7 and they survived -7," Noronha said. 

"They are pretty hardy, so even if they are caught in the soil which is frozen, it's not going to kill them."

Noronha said the fact that wireworm can survive at that temperature is bad news for P.E.I. farmers. 

"For most insects, it's the duration of the time that they have to spend in, let's say, -7. That's what kills them," Noronha said. 

"We don't have those winters here anymore and that's why populations are high. Because usually in previous years, mortality in the winter used to be very high, and that's why it kept the populations under control. But now we don't have those."

Even so, Noronha said a survey of click beetles, the adults of wireworm, is done every three years, and she said the 2019 survey showed the populations were down "significantly."

She said efforts by growers on P.E.I., using different techniques to reduce the populations of wireworm and click beetles, appear to be working, and they hope to do the surveys again in 2022. 

Hit hard

Hans Wilting knows first hand the devastation that wireworm can cause. 

He has been farming on the South Shore of P.E.I., around Canoe Cove and Meadowbank, for 25 years, growing potatoes primarily for french fries.

He said in 2005, all 300 acres of his potatoes were unmarketable because of damage from wireworm. 

"We first got hit by wireworm in 2005, and it was something new to P.E.I.," Wilting said.

"We got hit and we got hit hard by it, so we knew we had to do something, otherwise there would be no future."

Wilting has been involved in wireworm research since then.  

"I think we were probably one of the first ones to get hit by it. So that made us a good place to do the research, and having the research done on my own farm that I can see first hand what is working and what's not working," Wilting said.

Wilting said he has been seeing progress since traps were first installed on his land in 2007.

"The numbers in the pitfall traps were around 5,000 click beetles per trap," Wilting said.

"A couple of years ago, we were down to about a thousand per trap. And I think so far this year we're running around 130. So we've come a long way from where we were." 

Wilting said he has also made changes to the way he farms, to help combat wireworm, including using alternative crops such as mustard and buckwheat.

"We need to know as much as we can about it," Wilting said.

"They've been doing a tremendous amount of research, and certainly have gotten to know a lot about it. I think the biggest thing that we've discovered is it's one tough pest."

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