Last June when Bruce was scouting his 3,200 acres of barley, wheat, oats and canola in Yorkton, Sask., he was surprised to find the centre of a canola field almost bare, while the rest of his fields were fine. “The seed has rotted away — it’s no good,” Bruce said.
Sure enough, the first 60 feet of the field was healthy, with canola plants in the two-to three-leaf stage. On the other hand, the centre of his field was sparsely populated, with only one to two plants per square foot.
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Together we eliminated several factors including frost, seed quality and fertilizer. As I was digging up the soil looking for plants, I discovered a grey worm, about one and a half inches long, with a brown head. I knew we had found our culprit — the
pale western cutworm.
That night, we returned to the field and saw our pest actively feeding on the soil surface. In the life cycle of the pale western cutworm, eggs hatch from April to May and the larvae feed from May to July. In Bruce’s case, the field was summerfallow the year before, an ideal environment for moths to lay their eggs from August to September.
It is important to regularly scout all fields to check for low-density stands of plants or anything out of the ordinary. Do not assume that bare areas are slow-to-emerge plants.
One way to prevent pale western cutworm infestation on a summerfallow field is to make the last tillage operation at the end of July so that August rains create a crust on the soil, preventing moths from laying eggs in the soil.
Alternatively, the producer could wait an extra two weeks in the spring before seeding the field. Cultivating the field to remove any food sources starves the larvae. Also, the cultivation operation brings some larvae to the surface where cold weather will damage them.
Some registered crop protection products can be especially effective early on for controlling small patches. It is important to spray at night when the larvae are actively feeding.
In future, scouting fields often for irregular patches, checking soil and plant health both above and below ground will help Bruce avoid further pale western cutworm infestations.
