Tuta absoluta – All there is to know about leaf miner and its control

Tuta absoluta is a devastating leaf-mining moth with a strong preference for tomatoes.

Geographical distribution

It was first recorded in South America more than 30 years ago, the pest Tuta absoluta has recently crossed the Atlantic Ocean and spread rapidly throughout North Africa and Southern Europe and finally Africa. Since 2006, the moth has been found in an increasing number of Spanish provinces. In 2008 it was recorded in four Italian regions and in early 2009 in France and Tunisia.

Since then T. absoluta also has been detected in Malta, Morocco, Algeria, Turkey, Greece, Saudi Arabia, Syria, Israel, Iraq, Egypt, Lebanon and Jordan. Outbreaks of T. absoluta in the UK, the Netherlands, Portugal, Russia, Hungary, Romania, Bulgaria and Albania have been confirmed and the geographic spread still continues to increase widely in Africa.

It was first reported in Ethiopia before entering Kenya via Isiolo in 2014. Later it was reported in major tomato producing regions like Meru, Mwea/Kirinyaga, Narok and Loitoktok. Up to now it has spread in the whole country and has already crossed to the neighbouring countries like Tanzania.

Host plants and damage

To date, Tuta absoluta has been found mostly in tomato plants. The larvae attack leaves, stems and fruit.

Infestations in fruit may also result in secondary infections. There is limited evidence of significant damage in other crops, but it is known that T. absoluta also feeds on several species of Solanaceae; e.g potato. Also read: 6 steps to follow while investing in drip irrigation

If untreated T. absoluta can cause 50–100% yield reduction. Even when specific control programmes have been applied losses of more than 5% have been observed. In the case of medium to heavy infestations fruits are likely to be damaged, which may severely constrain the marketability of the produce.

Biology

Tuta absoluta reproduces rapidly with a life cycle ranging from 24–76 days, depending on the temperature. Full development of the moth from egg to pupa has been observed at mean temperatures between 14° and 30°C. Five generations per year have been recorded, but generations overlap and more than ten per year may occur under ideal conditions. Larvae of T. absoluta tend not to enter diapause if nutrition remains available and temperatures are favourable.

Life cycle of Tuta absoluta at different temperatures

14°C 76 days

20°C 40 days

27°C 24 days

Larva 4 Stages

11-19 days

Pupa

6-10 days

Adult

Eggs

3-5 days

Control measures in tomato crops

For effective control of Tuta absoluta, a combination of preventive, agricultural and non-chemical as well as chemical measures should be considered.

Preventive and agricultural measures:

• Greenhouse should be totally free from old tomato plant residues to prevent a carry-over of the pest from the

previous crop (at least six to eight weeks before new planting begins)

• Double door at the entrance to the greenhouse and insect netting over ventilation openings (9 by 6 threads/cm2)
• Continuous monitoring for T. absoluta with quality pheromone Delta traps at least ten days prior to transplanting the crop. This allows a quick response with control measures upon arrival of the pest.
• Water/oil-based traps in combination with pheromones, to reduce the T. absoluta population by mass adult trapping (20–50 traps/hectare inside greenhouses).

Chemical measures:

If non-chemical and other preventive measures are not enough for acceptable control of the pest, chemical support is necessary to keep the pest below the economically harmful level. Broad spectrum pesticides are difficult to use

in Integrated Pest Management (IPM) programmes. DuPont™ insecticides

Avaunt® (a.s. indoxacarb) and the new Coragen® (a.s. Rynaxypyr®) provide highly valuable tools for effective control of T. absoluta and are compatible with IPM programmes requiring the retention of N. tenuis and other beneficial insect populations.

Non-chemical measures (Biological control agents):

Most effective are the mirid bugs Nesidiocoris tenuis and Macrolophus caliginosus, predators of T. absoluta eggs and young larvae. Other suitable beneficials are Trichogramma spp. Good establishment of these beneficials in the crop contributes to effective population reduction of the pest.

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Recently there has been a rapid expansion in the search for new, effective natural enemies of T. absoluta. There is no doubt that the search for new, effective biocontrol agents for T. Absoluta will continue, and play a part in effective IPM.