The Cabbage seedpod weevil

Ceutorhynchus assimilis

Overview:

Type of Pest: Ceutorhynchus assimilis, commonly known as the Cabbage Stem Weevil, is a beetle species that poses a threat to oilseed rape (canola) and other cruciferous crops.

Physical Characteristics:

  • Size: Adults are small, typically around 3-4 mm in length.
  • Color: Grayish-brown to black, with a distinctive elongated snout.

Life Cycle:

  • Egg Stage: Eggs are laid in the stems of host plants, particularly oilseed rape.
  • Larval Stage: Larvae bore into the stem, feeding on plant tissues.
  • Pupal Stage: Pupation occurs within the stem.
  • Adult Stage: Fully developed adults emerge and may overwinter in plant debris.

Identification of Crop Infestation:

  • Stem Damage: Larval feeding results in characteristic tunnels within the stems.
  • Stem Girdling: Severe infestations can lead to stem girdling, affecting nutrient transport.
  • Crop Lodging: Weakened stems may lead to lodging, impacting crop quality and yield.

Management Strategies:

  1. Cultural Practices:

    • Crop Rotation: Rotate cruciferous crops to reduce the buildup of weevil populations.
    • Clean Fields: Remove and destroy crop residues after harvest.

  2. Biological Control:

    • Predators and Parasitoids: Encourage natural enemies such as ground beetles, spiders, and parasitoid wasps.
    • Birds: Birds, such as starlings, may feed on adult weevils.

  3. Chemical Control:

    • Insecticides: Application of insecticides may be necessary, especially during the vulnerable stages of the weevil.
    • Threshold Monitoring: Apply insecticides based on established economic thresholds.

  4. Resistant Varieties:

    • Plant Resistant Varieties: Consider planting oilseed rape varieties that exhibit resistance or tolerance to Cabbage Stem Weevil.

  5. Monitoring:

    • Scouting: Regularly monitor fields for signs of weevil damage.
    • Phenological Timing: Time insecticide applications based on the phenological stage of the crop and weevil life cycle.

Note: Cabbage Stem Weevils can be a challenging pest for oilseed rape cultivation. Integrated pest management (IPM) practices that include cultural, biological, and chemical strategies are crucial for effective weevil control. Always follow recommended guidelines and consult with local agricultural experts for site-specific recommendations.