The tomato pinworm,Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the global major destructive invasive pests was found to be occuring in India in the year 2014. The pest has spread from South America to several parts of Europe, entire Africa and has now spread to India. Plants are damaged by direct feeding on leaves, stems, buds, calyces, young fruit, or ripe fruit and by the invasion of secondary pathogens which enter through the wounds made by the pest. It can cause up to 90% loss of yield and fruit quality under greenhouses and field conditions.
Egg: Eggs are Small cylindrical, creamy white to yellow 0.35 mm long. Tuta absoluta deposits eggs on the underside of leaves or stems. Hatching takes place after 4-6 days.The egg colour varies from oyster-white to bright yellow, darkening in the embryonic phase and becoming almost black near eclosion.
Larva: The first-instar larvae are whitish soon after eclosion, becoming greenish or light pink in the second to fourth instars according to food (leaflet or ripe fruit, respectively). There are usually four instars. Larval period lasts 10–15 days. Tuta absoluta has a high reproductive potential. Larvae do not go to diapause stage while food is available.
Pre-pupa: The pre-pupae are lighter than the feeding larvae (first to fourth instars) and develop a distinguishing pink colouration on the dorsal surface. They leave the mines and build silk cocoons on the leaflets or in the soil, according to habitat. When pupation occurs inside mines or fruit the pre-pupae do not build cocoons.
Pupa: Pupae are obtecta with greenish coloration at first, turning chestnut brown and dark brown near adult emergence. Pupation takes place within 10 days on the leaf surface, in mines or in soil.
Adult: Adult moths are 5-7 mm long and with a wingspan of 8-10 mm, with silverish-grey scales, filiform antenae, alternating light or dark segments and recurved labial palps which are well developed.Adults are nocturnal and usually hide during the day between leaves. The pest may overwinter as eggs, pupae or adults. Adult female lays about a total of about 250 eggs during her lifetime. The total life cycle is completed in 30–40 days. There up to 12 generations per year.
Tuta absoluta prefers to feed on tomato, though other solanaceous plants, including potato, have been recorded as hosts. It is known to have many generations in a year and affects tomato in all growing stages.
Symptoms of damage
The larvae of T. absoluta mine the leaves producing large galleries and burrow into the fruit, causing a substantial loss of tomato production in protected and open filed cultivations. The larvae feed on mesophyll tissues and make irregular mine on leaf surface. Damage can reach up to 100%. This pest damage occurs throughout the entire growing cycle of tomatoes. Tuta absoluta has a vey high reproduction capability. There are up to 10-12 generations in year in favourable conditions. The larvae are very unlikely to enter diapause as long as food source is available. Tuta absoluta can overwinter as eggs, pupae and adults. Adult female could lay hundreds of eggs during her life time. Tomato plants can be attacked from seedlings to mature plants. In tomato infestation found on apical buds, leaves, and stems, flowers and fruits, on which the black frass is visible. On potato, mainly aerial parts are attacked. However damage on tuber also recently reported.
Management of T. absoluta
IPM strategies are being developed worldwide to control Tuta absoluta. Various active substances can be applied n combination with bio-rational control tactics. The integrated control method recommended employs, in order, (1) massive trapping before planting, (2) clearing the soil of crop residues, (3) the application of imidacloprid in the irrigation water 8-10 days after planting, (4) the application of either spinosad or Indoxacarb if occasional individuals of Tuta absoluta are observed, and (5) elimination of the remnants of the crop immediately after the last fruits have been harvested
In case of pheromone trap catches less than ten moths per trap per week control treatment treatments are recommended to be carried out mainly with bio-rational products, such as Bacillus thuringiensis and Azadirachtin. In case of pheromone trap catches more than ten moths per trap per week control treatment treatments are recommended to be carried out by combining bio-rational insecticides with synthetic chemical insecticides.
In low population densities mass trapping of the pest with pheromone baited water traps has also proved to be an effective control measure in Spanish outbreaks. An Average of 30-40 pheromone baited water traps should be placed per hectare of water. Mass trapping provide an environmentally friendly control measure.