REGINA — Ross Madsen surveyed his once-thriving canola crop with disgust.
“There’s nothing left of it,” he said.
In a matter of days, bertha army worms had eaten their way through the field, which the Wauchope, Sask. farmer estimated would have yielded 25 to 35 bushels per acre. He’s left with dried-out, chewed-up pods and thousands of worms.
The worms have infested canola fields in southwestern Manitoba and southeastern Saskatchewan. They’re also turning up in some mustard and flax crops.
“Where there’s a problem, it’s severe,” said Brad Hansen, extension agrologist at Estevan, Sask.
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The area hardest hit is the Redvers-Oxbow-Alida district in the southeastern corner. However, the worms have been found as far west as Tyvan, about 80 kilometres southeast of Regina, and in east-central areas near Esterhazy and Melville.
In Manitoba, the infestation is widespread throughout the southwest as far north as Birtle and east to Carman, said extension entomologist Andy Kolach. There is “tremendous variability” from field to field, he said.
Spraying under way
Extensive spraying is under way in both provinces, and some farmers were having to wait several days for the crop sprayers to arrive. For Madsen, the wait was too long.
According to a Manitoba Agriculture pest management bulletin, worm counts, the cost of spraying and the price of canola all have to be considered.
Several locations in a field, one square metre each, should be checked. The plants should be shaken to remove the worms, which should then be counted. Checks should be made in early morning or late evening.
A chart developed by the department shows if, for example, the value of the canola seed is $340 per tonne and the cost of spraying is $9 per acre, spraying would pay off if there are between 19 and 22 worms per square metre. Madsen found several hundred in an area he estimated at one-half metre by one-half metre.
Fall tillage could destroy some of the buried pupae and expose others to desiccation and predators. But even if 50 percent were to be destroyed through tillage, “we’ve got a problem next year,” Hansen said.
