Helicoverpa / Corn Earworm / Tomato Grub
Helicoverpa armigera; Helicoverpa punctigera
Native caterpillars that bore into tomatoes, sweet corn cobs, capsicums and beans. Major pest of fruiting vegetables.
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Identify from a photoBackground
Helicoverpa armigera (cotton bollworm) and the native Helicoverpa punctigera are the caterpillars behind holed tomatoes, tunnelled corn cobs and spoiled capsicums. They feed initially on leaves, then move into developing flowers and fruit. By the time frass is visible outside the fruit the damage is already done.
Helicoverpa armigera has well-documented resistance to several older insecticide groups, so management in both commercial and home settings relies on timely intervention before larvae tunnel inside.
How to identify
- Eggs: tiny white-cream domes with fine ribs, laid singly on young foliage or flower structures
- Larvae: up to 40mm long, highly variable: pale green, pink, brown or nearly black with darker longitudinal stripes
- Adults: stout buff-coloured moths with a darker crescent on the forewing
- Damage: holes in tomato fruit, hollowed corn cob tips, bored capsicums, chewed bean pods
Life cycle
Eggs hatch in 3-5 days. Six larval instars over 2-4 weeks. Pupation in soil for 2 weeks or longer. Multiple generations spring through autumn.
Weather triggers
- Temperature: 15-35°C
- Moth flights peak after warm humid nights. Larval development fastest 25-30C.
Peak season (southern hemisphere)
Red = active season · Dark red outlined = this month
Affected vegetables & crops
Click any crop to see current prices and growing info.
Climate zones at risk
Organic & low-impact control
- Bacillus thuringiensis (Btk, Dipel) sprayed on flowers and young fruit trusses. Must be consumed by the larva while it's still outside the fruit
- Regular inspection and hand removal of caterpillars
- Release of Trichogramma egg parasitoids (commercially available)
- Spinosad for higher pressure
Chemical control
- Resistance management is critical. Commercial growers rotate groups; home gardeners should default to Btk or spinosad
- Avoid repeated use of synthetic pyrethroids in home gardens
Always read product labels. Registrations change.
Prevention
- Inspect plants at least twice weekly from flowering onwards
- Remove affected fruit immediately and destroy. Do not leave on plant
- Cultivate soil at the end of the season to expose pupae
Companion planting
Flowering insectary plants support parasitoids. Decoy plantings of maize (corn) in ornamental garden plantings can act as a trap crop if destroyed before larvae mature.
Biosecurity
Native/established. No quarantine concern.
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