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Sunflower head borer Helicoverpa armigera Photo: Aneel Mohite, Rashtrasant Tukdoji Maharaj Nagpur University, India · CC BY-SA 3.0 · source ↗

Sunflower head borer (Helicoverpa armigera)

The cosmopolitan polyphagous lepidopteran Helicoverpa armigera Hubner is the most damaging insect pest of sunflower (Helianthus annuus) in India. As a "head borer" on sunflower it feeds on developing florets and seeds inside the maturing capitulum (flower head), causing 30-60% seed loss in untreated rabi-summer crops in Karnataka, Andhra Pradesh, Telangana, Maharashtra and Tamil Nadu.

Identification

  • Adult: stout-bodied moth, 18-20 mm long, forewings pale yellow-brown with a black kidney-shaped mark, hindwings creamy with a broad dark border
  • Egg: spherical, 0.5 mm, creamy-white, laid singly on the bracts and back of the flower head and on upper leaves
  • Larva: variable colour (pale green to brown to almost black), 30-40 mm at maturity; characteristic dark lateral stripes along the body; the head capsule is yellowish
  • Damage symptom: circular bored holes in florets and across the seed-bearing disc; chewed unripe seeds and frass packed inside the head; secondary fungal rot at the bore wound. In a severely-attacked head 30-70% of seed-bearing area can be destroyed

Hosts and lifecycle

H. armigera is highly polyphagous — known pulses, cotton, tomato, chickpea, chilli, redgram, maize and many vegetable hosts cycle the pest year-round in Indian conditions. Lifecycle on sunflower takes 28-35 days, with 4-5 overlapping generations per year. Egg laying on sunflower begins at the star-bud stage and peaks at 50% flowering; larvae feed on petals first and then bore through the disc into the developing seed. Pupation occurs in the soil. Adults are strong fliers and respond to pheromone traps; populations build up early on chickpea and redgram and migrate to flowering sunflower in February-April for rabi-summer crops.

Damage and economic impact

Untreated rabi sunflower in Anantapur, Mahabubnagar, Raichur and Karnataka eastern dry zone records 30-60% seed-yield loss from head-borer attack. Yield loss is non-linear: a head attacked at the 50% flowering stage can be a near-total write-off because seed set is destroyed. The pest is also a key reason farmers shift away from sunflower toward less pest-sensitive oilseeds such as safflower.

Management

ICAR-IIOR and AICRP-Sunflower integrated package:

  • Monitoring: pheromone traps at 5 per hectare set up at star-bud stage; spray threshold is 1-2 larvae per head or 8-10 moths/trap/night
  • Cultural: avoid continuous cropping with chickpea or redgram on adjoining fields; deep summer ploughing to expose pupae; remove and destroy attacked heads
  • Biological:
  • Egg parasitoid Trichogramma chilonis released at 1.5 lakh/ha twice — at star-bud stage and 50% flowering
  • HaNPV (Helicoverpa armigera nucleopolyhedrovirus) at 250-500 LE/ha, 2 sprays at 50% and 100% flowering; mix with jaggery 1% and apply in evening
  • Neem oil 0.5% or NSKE 5% spray at early larval stage
  • Chemical: at 50% flowering and 10-12 days later: emamectin benzoate 5 SG at 0.4 g/L, chlorantraniliprole 18.5 SC at 0.3 ml/L, spinosad 45 SC at 0.4 ml/L, or flubendiamide 39.35 SC at 0.2 ml/L. Avoid synthetic pyrethroids in the pre-flowering window because they decimate pollinators that sunflower requires for seed set
  • Resistance management: rotate IRAC mode-of-action groups across the 2-spray window; do not repeat the same molecule

See also: Sunflower crop, KBSH-44 sunflower hybrid, MSFH-17 sunflower, Pheromone traps, Helicoverpa armigera in fruit crops.

Sources

  1. Sunflower pest management. ICAR-Indian Institute of Oilseeds Research, Hyderabad.
  2. Helicoverpa armigera factsheet. CABI Plantwise.
  3. Sunflower package of practices. ANGRAU.