The damage caused by these agromyzid flies (leaf mines) should not be confused with that produced by Tuta absoluta Meyrick (lepidopteran géléchiidae) whose mines on leaves are whitish and larger than those of leaf miners (figures 1 and 2). These mines eventually necrode, suggesting a severe attack of late blight. This moth can also attack fruits and produce necrosis on the peduncle, or on other places of tomatoes. This pest can cause considerable losses on tomatoes, reaching 100% in certain production areas in Europe.

T. absoluta , a microlepidoptera of the Gelechiidae family, has been rampant for many in several countries of South America (Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Paraguay, Peru, Uruguay, Venezuela). This insect was first detected in Europe in 2006 in Spain. It subsequently spread in this country and reached many other countries of the Mediterranean Basin (Algeria, Egypt, Greece, Israel, Italy, Libya, Morocco, Syria, Tunisia, Turkey ). It appeared in France from 2008, in particular in Corsica initially, then in the south-east of France.

The larvae of T. absoluta dig mines and galleries on the aerial organs of the tomato. The leaves show mines, irregular whitish spots gradually becoming brown and necrotic. Only the tissues of the mesophyll are affected, the epidermis remains intact. Heavily parasitized leaves can completely necrode. Green fruits, like ripe fruits, are parasitized; they are more or less strewn with galleries and exit holes. These sometimes allow secondary invaders to cause various rots, during cultivation and during their conservation. Note that parasitized fruits are often unsalable. Galleries may appear on young stems, disrupting plant development. Black feces are visible here and there on the affected organs; they also materialize the actions of this pest.

T. absoluta goes through 4 stages of development: egg, larva, pupa and adult. The duration of its biological cycle varies according to the temperature in particular; for example, it would be approximately 24 days at 27 ° C. There could be up to 10 to 12 generations per year.

This insect spends the winter in the form of eggs, pupae or adults. These are nocturnal and usually hide between the leaves during the day. The main host of T. absoluta is tomato, but it can also occasionally parasitize various other cultivated Solanaceae species (eggplant, pepino - Solanum muricatum , pepper, potato) and wild ( Datura stramonium, D. ferox , Lycium chilense, Lycopersicon hirsutum, Nicotiana glauca, Solanum lyratum, S. nigrum, S. elaeagnofolium, S. puberulum ...).

The eggs are tiny and invisible to the naked eye, measuring less than a millimeter. They are cylindrical in shape and are cream to yellowish in color. They hatch 4 to 6 days after laying. Four successive larval stages. The larvae are a few millimeters long. First cream colored, then greenish to pinkish, they dig galleries on the aerial organs of the tomato. The chrysalis stage takes place either inside the galleries, or on the surface of the host, or on the ground. Pupation lasts 10 to 12 days.

The adults, butterflies, are 5 to 7mm long and about 10mm in wingspan. They have a silvery gray to brown tint with black spots on the forewings. Males are a bit darker than females. Their antennae are threadlike. The approximate lifespan of adults is 6-7 days for males and 10-15 days for females. Each female can lay 40 to 250 eggs, often located on the underside of the leaves or on the young tender stems and sepals of young fruits.

During cultivation

- eliminate the parasitized leaves, stems and fruits , and burn them quickly. It will be the same for the plants or the plants too attacked;
- pluck regularly parasitized plants and remove the leaves;
- do not leave parasitized plant debris in heaps on the ground in or near greenhouses or tunnels, which allows this pest to remain locally;
- fruits that have fallen to the ground must be collected and destroyed ;
- several products * can be used to control the development of T. absoluta, their list is available on the e-phy site . Cases of resistance to insecticides having been reported for T. absoluta, alternate the active ingredients, and respect the doses and number of applications recommended per year;
- block the openings and openings of greenhouses and tunnels to prevent adults coming from outside. Install nets insect-proof ;
- at the end of cultivation, quickly remove the crop residues and burn them ;
- in greenhouses, disinfection of the soil can be considered in order to destroy the pupae, especially in the case of monoculture of tomatoes. In the open field, tillage will help reduce their number.


Next crop

- monitor the quality of the plants and refuse those showing suspicious symptoms.
- pull up and burn the affected plants then carry out a treatment;
- eliminate the weeds mentioned above likely to harbor T. absoluta (under shelter, open field and surroundings);
- set up pheromone traps (water traps, Delta type, Mc Phail type) in order either to detect this insect pest early and to assess the potential risk for the crop, or to reduce the population present.
Several auxiliary insects have been reported as more or less effective against this lepidoptera: Nesidiocoris tenuis, Macrolophus caliginosus, Trichogramma pretosium, Trichogramma sp, Pseudoapanteles dignus, Dineulophus phthorimaeae, Cornua sp., Podisus nigrispinus ;
- implement the recommended measures during cultivation.
 
 

Last change : 07/08/21