South American tomato moth

The larva of the South American tomato moth, Tuta absoluta, pierce into leaves, stems and fruits and causes economic damage with potential harvest losses off up to 50-100% in untreated crops. T. absoluta is native to South America and since 2006 it is also found in the Mediterranean area and in Western Europe.

Damage

Tuta absoluta attacks plants of the nightshade family, but tomato plants are the most affected. Damage manifests itself by the presence of bladder-shaped mines produced by the larvae while they feed on mesophyll tissue. The larva deposits its excrements at the end of the mine. After some time, mines turn brownish and become necrotic. Larvae can leave mines to attack other parts of the plant; for instance, they bore into young stems and fruits. Close to a borehole heaps of dark, granular excrement (frass) is often found. Affected fruits are unsuitable for sale or consumption.

Description and life cycle

Tuta absoluta is a micro moth of 6-7 mm long. It is gray brown with dark spots on the anterior wings. The small eggs are cylindrical, creamy white to yellow and about 0.36 mm long. The 1st larval stage is cream-coloured and about 0.5 mm long. As the larvae grow, they turn yellowish-green and have a black stripe at the back of their heads. Full-grown larvae are greenish pink. Larvae of the 3rd stage are about 4.5 mm long and those of the 4th stage are about 7.5 mm. The larva pupates in a silk cocoon which is about 8 mm long.
The life cycle takes about 10 weeks at 15°C and 3 weeks at 25°C. It can breed 10 to 12 generations a year. Adults are mainly active at night and hide between leaves during the daytime. Over her lifespan, each female deposits more than 200 eggs. Eggs are deposited on the underside of leaves or on young stems and sepals of unripe fruits. After 3-5 days, the young larvae hatch and are ready to penetrate plant tissues. After they pass through the 11-19 days of the 4 larval stages, they pupate in the mine, on the leaf or in the soil. The pupal stage lasts for 6-10 days. T. absoluta can overwinter as an egg, pupa or adult. No overwintering has been observed in the Mediterranean. Males live about 6-7 days and females 10-15 days.