Bollworm, also known as tomato fruit worm or American Bollworm, Helicoverpa armigera, are small caterpillars (about 30mm long, slightly more than 1 inch) that have prominent rows of dark bumps on their backs. Mature worm’s colour varies from dark grey to light brown and have lengthwise stripes on their bodies. The adult form of the worm is a moth which is nocturnal.
The worm thrives in warm climates. They are at their most destructive when damaging only part of one fruit before moving to the next.
The fruit have the characteristic small corky hole at the base of the pedicel. The inside of the fruit has a watery cavity and starts to rot. The fruit is unmarketable. The American Bollworm attack citrus, deciduous fruit trees, grapevines, strawberries, beans, brinjals, crucifers, cucurbits, potatoes, tomatoes and garden flowers.
- Monitor: pheromones
- Biological: several egg and larval parasitoids
- Chemical: carbaryl, chlorpyrifos, cyfluthrin/piperonyl butoxide, deltamethrin, fenitrothion phenothrin/tetramethrin.
Natural predators that are important are;
- Braconid wasps (Bracondiae). The wasps are attracted to small flowering plants which are rich in nectar flowers. Ideal flowers are caraway, coriander, dill, sweet fennel, spearmint and tansy. Ideal herbs are buckwheat, white sweet clover, golden marguerite, potentilla and statice. Leave weeds such as corn spurry, common knotweed, mustard and stinging nettle (ideal around security fences).
- Lacewings (Chrysopa spp., Chrysoperia spp.). Lace wings are attracted to plants that produce pollen and nectar flowers such as coriander, dill, daisies and fennel. Some wees are also beneficial such as Queen-Anne’s lace or yarrow. Leave them to bloom next to pathways and farm roads. There are two species available on the commercial market.
- Tachinid flies and
- Minute pirate bugs.
In order to have additional control supply these insects with enough plant material to breed around the hydroponic farm. They will fly around and penetrate the growing area and feed on their pray, reducing spraying cost.