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Yield and Quality Problems Caused by Western Bean Cutworm (WBC)

Western bean cutworm (WBC) can cause serious quality issues in corn.

Western bean cutworm (WBC) grabbed headlines in the fall of 2009. It’s a pest that’s new to Ontario and unfortunately it’s on the move. There were some pockets in Ontario where damage was quite extensive.

Although Western bean cutworm is native to North America, it did not materialize in Ontario until recently. That initial fall saw a scramble for information on this new pest and for crop protection tools to minimize its destruction of key crops in Ontario.

What is WBC?

  • A pest of field, sweet and seed corn and dry beans
  • It feeds on the corn ear and can cause a decrease in yield and quality
  • WBC overwinters in soil chambers
  • Young WBC larvae feed on tassels and silks and then tunnel into the ear 

Why are they just showing up now?

Several factors may be causing WBC to increase, including reduced use of foliar insecticides and increased no-till.

Scouting techniques

  • According to the Ontario Ministry of Agriculture, Food and Rural Affairs, stay on top of field scouting when the corn crop is in the pre-tassel to full-tassel stages
  • Scout 20 plants in five areas of the field from early July to the end of August
  • Look for egg masses and young larvae on the top three to four upper leaves
  • Egg masses are white when they are newly laid and turn purple when they are ready to hatch within one or two days
  • Egg hatch is when an insecticide treatment is most effective 

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