Managing Tuta Absoluta Through Direct Interference Between Natural Enemies Of Tuta Absoluta On Tomato.
Tuta absoluta is a specie of moth in family Gelechiidae known by the common names tomato leafminer or South American tomato moth, In Nigeria farmers call it tomato ebola. It is well known as a serious pest of tomato crops in Europe and South America.
The larva feeds voraciously on tomato plants, producing large galleries in leaves, burrowing in stalks, and consuming apical buds and green and ripe fruits. It is capable of causing a yield loss of 100%.
Tomato is the main host plant, but Tuta absoluta also attacks other crop plants of the nightshade family, including potato, eggplant, pepino, pepper and tobacco. It is known from many solanaceous weeds.
The female moth lays up to 260 eggs, mostly singly, on leaves, stems and young fruit. The larvae bore between the epidermal layers of the leaf creating mines and, when older (at the 3rd to 4th instar or later developmental stage of the larva) they leave these mines and travel to new locations to mine again.
Young larvae usually attack the leaves, but can be found in growing points and in the flower. Later stage larvae tend to attack the fruit. Pupation happens in the mine, outside the mine, or in the soil.
The adult moth has a wingspan around one centimeter. In favorable weather conditions eight to ten generations can occur in a single year.
Some populations of T. absoluta have developed resistance to organophosphate and pyrethroid pesticides. Newer compounds such as spinosad, imidacloprid, and Bacillus thuringiensis have demonstrated some efficacy in controlling European outbreaks of this moth.
Signs and symptoms
Common signs and symptoms of Tuta absoluta on fruit and stems include:
- Puncture marks,
- Abnormal shape,
- Exit holes,
- Rot due to secondary infective agents, and
- Frass (fine powdery material that plant-eating insects pass as waste after they digest plant parts).
Attacked tomatoes are easy to spot by the exit holes and the dried frass produced by the last larvae as they pupate.
Signs of damage on the fruit are often observed under the calyx (green leaf-like organ above the fruit). Cracks and crevices on containers should be checked for the presence of pupae.
Management (Biological control)
The sex pheromone for T. absoluta has been identified by researchers at Cornell University and has been found to be highly attractive to male moths. Pheromone lures are used extensively throughout Europe, South America, North Africa and the Middle East for the monitoring and mass-trapping of T absoluta.
The combined use of pheromones as well as specific light frequency proved to be effective in suppressing the Tuta absoluta population and keeping it within the economic threshold as it disclosed by Russell IPM in a United Kingdom patent.
Trichogramma achaeae has also been evaluated as a biological control agent of different lepidopteran pests.
Among possibilities for controlling this pest, oophagous parasitoids have shown promising potential for controlling the pest before yield decrease, and one species in particular, Trichogramma achaeae, is currently proposed in Spain and France for inundative biological control of Tuta absoluta.
In greenhouses, Miridae predators are also common on tomato and usually used against whiteflies. Despite the fact that these predators do not attack Trichogramma achaeae adults, they may partially decrease the overall impact of the parasitoid on Tuta absoluta if intraguild predation occurs on Trichogramma achaeae-parasitized eggs.
Indeed, it could reduce parasitoids’ offspring and thus their potential additional effect on Tuta absoluta.