HEAD BORER OF SUNFLOWER: Pest Overview, Symptoms & Management

HEAD BORER OF SUNFLOWER: Pest Overview, Symptoms & Management

1. Pest Overview

Scientific Classification

  • Scientific Name: Helicoverpa armigera (Hubner, 1808)
  • Order: Lepidoptera
  • Family: Noctuidae
  • Common Names: Sunflower Head Borer, Helicoverpa, Cotton Bollworm

Morphology & Identifying Features

Larvae (Caterpillar):

  • Length: 25–40 mm at full growth.
  • Color: Green, brown, or reddish with distinct longitudinal stripes and black spots on each segment.
  • Head: Brown, hard-shelled, with strong mandibles for boring into sunflower heads.
  • Behavior: Initially feed on leaves and buds, later bore into flower heads and developing seeds.

Pupae:

  • Brownish, smooth, 15–20 mm long.
  • Pupation occurs in soil at 2–5 cm depth near the plant base.
  • Duration: 7–10 days depending on temperature.

Adult Moth:

  • Wingspan: 30–40 mm.
  • Forewings: Brownish with dark mottling; hindwings pale cream or grey.
  • Nocturnal: fly at night, hiding in leaves during day.
  • Females are prolific egg layers (200–300 eggs each).

Life Cycle & Reproduction

  1. Egg Stage: Laid on flower buds, bracts, or leaves; incubation 3–5 days.
  2. Larval Stage: 2–3 weeks, consisting of 5–6 instars. Larvae bore into sunflower heads and feed on seeds.
  3. Pupal Stage: Soil pupation; lasts 7–10 days.
  4. Adult Stage: Lives 10–15 days; mates at night and lays eggs.
  • Generations: 3–5 per year depending on climatic conditions.
  • Peak Activity: Coincides with flowering and seed formation stages of sunflower.

Seasonal Occurrence

  • Early infestation occurs during bud initiation.
  • Maximum damage observed during flowering and seed filling.
  • High activity in warm and dry weather conditions; moderate to low in humid, rainy periods.

2. Host Range

  • Primary Host: Sunflower (Helianthus annuus).
  • Secondary Hosts: Chickpea, cotton, tomato, maize, sorghum, and certain legumes in the surrounding area.
  • Regional Prevalence:
    • India: Maharashtra, Karnataka, Andhra Pradesh, Rajasthan, Tamil Nadu. 
    • Globally: Widespread in Africa, Australia, Southeast Asia, and South America.

3. Symptoms & Identification

Visible Damage

  • Bored flower heads and buds; petals with holes or frayed edges.
  • Larvae feed on developing seeds, leaving hollow cavities.
  • Premature drying or rotting of sunflower heads.
  • Irregular flowering and poorly formed heads in severe infestations.

Signs of Infestation

  • Presence of larvae inside flower heads.
  • Accumulation of frass (excrement) near entry holes.
  • Drooping or wilted heads due to larval feeding.

Impact on Yield & Quality

  • Seed loss can range from 10–50% depending on infestation intensity.
  • Reduced oil content and quality due to damaged kernels.
  • Economic losses are significant in high-density infestations.

4. Monitoring & Detection

Field Scouting

  • Inspect 10–15 randomly selected plants per hectare during flowering.
  • Check flower heads for bore holes, larvae, or frass.
  • Conduct scouting weekly during peak season.

Pheromone & Light Traps

  • Pheromone traps attract adult male moths, providing early warning of population surge.
  • Trap count: Threshold for action is 5–10 moths per trap per week.
  • Light traps can supplement monitoring but are less specific.

Economic Threshold

  • Initiate management when 5–10% of flower heads are infested or larvae are present.
  • Early-stage interventions are more effective and cost-efficient.

5. Management Strategies

A. Cultural Practices

  • Crop Rotation: Alternate sunflower with non-host crops like cereals to reduce pest build-up.
  • Sanitation: Remove and destroy infested heads and crop residues post-harvest.
  • Sowing Time Adjustment: Early or late sowing to avoid peak pest emergence.
  • Intercropping: Legumes or trap crops may help reduce pest pressure.

B. Biological Control

  • Natural Predators: Ladybird beetles, lacewings, spiders, and predatory bugs.
  • Parasitoids:
    • Trichogramma chilonis – egg parasitoid.
    • Bracon hebetor – larval parasitoid.
  • Promote habitats like flowering plants around fields to encourage beneficial insects.

C. Chemical Control

  • Recommended Insecticides:
    • Spinosad (0.1%)
    • Emamectin benzoate (0.004–0.005%)
    • Chlorantraniliprole (0.005%)
    • Indoxacarb (0.0075%)
  • Application Guidelines:
    • Spray during early larval stages for maximum impact.
    • Apply in the evening to avoid harming pollinators.
    • Rotate chemicals to prevent resistance development.
  • Safety: Wear protective clothing, follow label instructions, and avoid drift onto non-target crops.

D. Integrated Pest Management (IPM)

  • Combine cultural, biological, and chemical methods.
  • Monitor regularly to avoid unnecessary sprays.
  • Focus on preventive measures and natural enemy conservation.
  • Keep records of pest incidence to plan future management.

6. Farmer Advisory Tips

Preventive Measures

  • Timely sowing and selection of resistant/tolerant sunflower varieties.
  • Maintain field hygiene and proper irrigation.
  • Monitor flowering stage closely; anticipate pest build-up.

Early Infestation Remedies

  • Remove and destroy small infested heads.
  • Use biopesticides like Bacillus thuringiensis (Bt) sprays on early larvae.
  • Employ neem-based formulations as a safer alternative.

Post-Harvest Management

  • Collect and destroy all leftover infested heads.
  • Store harvested seeds in dry, pest-free conditions.
  • Ensure proper drying to prevent fungal and pest damage.

✅ Key Takeaways:

  • Early detection through scouting and pheromone traps is critical.
  • Combining cultural, biological, and chemical controls reduces losses and pesticide use.
  • Timely interventions protect yield and maintain seed quality.
  • Farmer education on lifecycle and pest behavior ensures sustainable pest management.
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