Corn Rootworm 2018.1 Fact Sheet

Click here for FACT SHEET PDF (with photos)

Western Corn Rootworm

  • Detected for the first time in the Fraser Valley in 2016 and reached record levels in local corn fields during the 2017 season.
  • Single most important factor contributing to economic loss and shifting management practices in corn growing regions in North America.


Adults:  clip corn silks which interferes with pollination and may result in poorly-filled cobs.  Beetles and frass can contaminate fresh market sweet corn.  They feed on the top layer of leaf tissue and eat the flowers of a variety of crops, including cucurbits.

Larvae:  feed on corn roots reducing structural integrity and nutrient uptake resulting in weak, unstable plants.


Larvae:  White, 3-15mm long; brown head capsule, 6 legs, with a dark patch at the end of the abdomen.

Adults:  Yellow, ~ 6mm long beetles with 3 black parallel stripes (females) or a solid black patch (males).


Adult beetles:  Active in late July-August.  Visually inspect 20 plants at 5 locations for adults and feeding damage.  In sweet corn, consider a foliar spray if there are more than 10 adults per plant.  For forage corn, damage by beetles is of less concern – however presence of adults is an indicator that larvae will be present in the next season and will cause damage.

Larvae:  Monitoring for larvae is useful to determine if the insect is present in a field.  Sample weak-looking areas in the field by digging around the roots and lifting it onto a dark plastic sheet.  Search through corn plant roots and crowns for larvae.  For fields where whole plants are missing, the cause is more likely due to wireworm than western corn root worm.


Entire Fact Sheet contains more information on management.