Chilli fruit borer: scouting a pest that lives inside

The window

The larva is exposed for a short period — as an egg on the leaf or flower, and as a very small larva before it enters the fruit. After that it is inside, feeding, and a contact spray does nothing.

That is why calendar spraying works badly and monitoring works well.

Monitoring

Pheromone traps for the adult moths, from flowering onward. A rising catch is the signal to look for eggs, not the signal to spray.

Scout the flowers and young fruit twice weekly. Look for small entry holes at the calyx end, and for frass. Cut open a few fruit at random — the damage is invisible from outside until it is advanced.

Count. A threshold reached is a spray justified; a moth in a trap is not.

Managing it

• Rotate the mode of action every spray. This pest has developed resistance to several groups where one was used repeatedly.
• Target the flowers and young fruit, where the eggs are, with enough water to reach into the canopy.
• Evening application, when the larvae are active and the beneficials are not flying.
• Remove and destroy bored fruit at each picking. Every one carries a larva that will pupate in your field.
• NPV and neem-based products at low to moderate pressure, keeping the strong chemistry for when it is genuinely needed.
• Do not spray broad-spectrum early for light thrips or aphid pressure — the natural enemies removed then are what would have kept borer numbers down later.

Tobacco caterpillar

Often present alongside, feeding on leaves and fruit. Egg masses are laid in clusters on the underside of leaves and are covered in brown hair. Finding and destroying egg masses and the early gregarious larvae — which feed together in one place before dispersing — removes hundreds of larvae for a few minutes of work.

The pattern

Fields that spray on a calendar from week three have worse borer problems by picking than fields that scouted and sprayed twice at threshold. The difference is not the chemistry.

Read the label and the leaflet on the pack before use. The approved crops, dose and waiting period printed there are what count.