HortFACT
Identification
The tomato fruitworm (originally named Heliotis armiger) is also known as corn earworm, tobacco budworm, etc., depending on the kind of plane on which it is feeding.
Adults vary in colour, but are typically brown to greyish brown with a series of dark, irregular, transverse lines across the front wing. There is a darker area towards the tip with a paler band near the margin and dark spot almost at the centre. Hind wings are pale at the bases with the outer half of each much darker. Adult moths have a wingspan of about 35 mm. They are nocturnal in habit, flying, mating, and laying eggs at dusk.
The eggs are laid singly, under leaves, on buds, or on maize silks, etc. They are small, hemispherical, and creamy white.
The colour of larvae [caterpillars] can vary on a single food host from differing shades of green to pink, brown, or almost black. There is a double dark line down the middle of the back, and a broad pale stripe runs along each side of the body. There are five instars [larval stages], and fully grown larvae are about 35-40 mm long.
The pupae are dark brown. Pupation [change from a larva to a pupa] occurs in smooth-walled cells 70 mm or more underground.
Host Plants
The host range is very wide. Larvae feed mainly on flower buds, flowers, developing seed, and fruits; and sometimes on foliage. They are a major pest on maize, tomato, lucerne, lupins, and conifer (pine) seedlings. They also attack other cultivated plants including peas and beans, pumpkins and marrows, tobacco, clover, and linen flax, and a great number of ornamental herbaceous plants and shrubs.
Damage
Newly hatched larvae feed on surface tissues of the plant, but cause most damage by feeding on the buds and fruiting parts of the plants, and eating their way into flower buds, seed pods, and young fruits. On tomatoes, beans, etc., larvae bore completely into the fruit. on maize, after eating the silks, they feed on the soft seeds at the top of the cob. Foliage can be completely stripped from pine seedlings.
Distribution
Tomato fruitworm, which is also known from Africa, Southern Europe, Asia, and Eastern Australia, is found throughout the lowland areas of New Zealand.
Life-Cycle
| Egg |  |
| Larvae | |
| Pupae | |
| Adult | |
| Month | |
| Note: Coloured bars indicate periods of peak activity in each of the life cycle stages | |
Pupae overwinter in the soil, and the adults emerge with the warmer spring weather, beginning about October in northern areas and later in southern regions. There are probably three generations in a year.
The time spent in each stage depends on weather and locality; eggs hatch in about 7-10 days and larvae feed from 4-6 weeks. Development may continue in the pupal stage, with adults emerging in 2-3 weeks, but many larvae can transform into a pupal diapause (arrested development stage] for longer periods or until the following spring. The factors which induce diapause are not well understood, but seem to relate to shortening day length, relative dryness, and lower temperatures.
E. W. Valentine