British Columbia

Armyworms on the march through B.C. crop fields

Voracious insect larvae are munching their way through crops used to feed livestock in British Columbia.

The moth larvae are drawn to grass, hay and cornfields

Armyworms have been seen in B.C. before, but never in this amount. (CBC)

A large garrison of armyworms have attacked Vancouver Island and B.C.'s Lower Mainland.

Staying true to the adage an army marches on its stomach, the caterpillars are feasting their way through a number of crop fields in the Alberni Valley area.

"They're voracious feeders, particularly in the last stages of their life," said Ministry of Agriculture entomologist Tracy Heuppelsheuser.

"They can defoliate grass fields, or corn fields, within a few days."

Since first being reported this summer on Vancouver Island, the insects have now been seen on fields in Surrey, B.C., Delta, Abbotsford and further up the Fraser Valley.

Heuppelsheuser says true armyworms are a moth larvae ranging in colour from greeny-brown to dark black with tan markings. She says the insect is normally native to the southern United States and Mexico.

Strong spring winds can blow the adult moths north, where they settle in lush green growth and lay eggs on grass blades or corn stalks.

Unique devastation

Heuppelsheuser says there are records of armyworm moths at the Royal B.C. Museum, and they have been found by collectors in the past. However she says this year's outbreak is unique due to the prolific number of worms.

"No one I've ever talked to remembers any kind of devastation like we're experiencing this year," said Heuppelsheuser.

The main concern for farmers is the worms attraction to crops used to feed livestock. Pastures, hayfields, cornfields — none are safe from the animal.

Heuppelsheuser says it is very difficult to predict if a growing season will be abundant in the worms. For that reason, she cautions farmers to monitor their fields closely. She says if five or more worms are seen in a square foot, then the farmer can expect crop loss.

At that point, Heuppelsheuser says B.C. farmers have been forced to make the difficult decision of harvesting their crop early, or spraying their fields with pesticides.

Heuppelsheuser has yet to trace this particular wave of armyworms to the southern parts of the continent, but hopes her continuing research will reveal this batch's origins in the coming weeks.

With files from All Points West