Farmers in the Alberni Valley are on edge after elevated numbers of winter cutworm larvae were discovered in fields last fall. However, Alberni-Clayoquot Regional District (ACRD) officials are saying there is no cause for alarm.
Lisa Aylard from Stonehaven Farm and the Alberni Valley Farmers' Institute discovered larvae eating patches of her fields last October. Her mind immediately went to the 2017 outbreak of true armyworm that devastated crops throughout the Valley in June and July of that year.
"We've never experienced this other than the armyworm problem. This is basically mimicking what we had in 2017," she said at a meeting of the ACRD's agricultural development committee.
Winter cutworm, or Noctua pronuba, is different from true armyworm, said Amy Needham, the ACRD's sustainability planner. True armyworm does not overwinter on Vancouver Island, and only arrived in the region after the moths were blown up from the United States, laid eggs and the larvae started eating the crops.
The last time true armyworm moths were detected in traps in the Alberni Valley was in 2021, ACRD agricultural development committee chair Heather Shobe said in a meeting last October.
Needham said Noctua pronuba is a "completely different insect" from true armyworm and has been present in Canada since 1979. It feeds on a wide variety of plants. Last fall "the numbers built up to the point where we were seeing crop damage," she said.
Needham, who spent 15 years in integrated pest management in the prairies, and Aylard collected samples from Stonehaven and several other locations in the Alberni Valley. Needham consulted provincial entomologist Emily Grove and has passed on samples to provincial and federal departments.
Needham said the winter cutworm population isn't large enough to call an outbreak, and most sightings have been in the Alberni Valley with a few elsewhere in the mid-Island. "This insect has always been around at background levels," she said. "It's elevated populations in some areas. I wouldn't classify it as an outbreak."
She said there is no cause for concern: the damage she saw in the fall was "defoliation" in patches and there was no evidence of root damage. "It's no more damaging than just taking another cut of hay."
The ACRD will be setting traps in March where large numbers of winter cutworm larvae were discovered to monitor how many mature to large yellow underwing moths (she will also set different traps later in the spring for armyworm, at the behest of the Farmers' Institute). She cautions the traps are not a control measure, they're a way to gauge whether this year was an anomaly or setting up for an outbreak.
She said cutworm "is quite palatable to predators" and there is a chance the population could be decimated by disease before it becomes a problem. The best control method for people who find the Noctua pronuba larvae or moths is "picking and squishing." For farmers the best method is to "make sure your crops are healthy," she said.
She is hoping with her research in the Alberni Valley to fill in the gaps of knowledge about winter cutworm or Noctua pronuba in the region—she found very little information about it when she first went looking for it, and she had never heard of it in more than a decade working in pest management in Alberta.
