Résumé:
T h e proliferation of the tomato leafminer Tuta absoluta Meyrick (Lepidoptera:
Gelechiidae), during 2008s and 2009 in all Mediterranean Basin profoundly destabilized the
sector of tomato because it destroyed a big cultivated surface and led the farmers to make
additional costs for the chemical fight. This method very used because of its spectacular
effects turned out ineffective at the end of a few months. This new phytosanitary problem of
the tomato led to the changes of the strategies of fight with the introduction of the other
alternative means as the biological fight. We proposed the use of predatory bugs (the mirides)
which are available in Algeria.
In a preliminary work, we followed the dynamics of the populations of T. absoluta from an
artificial infestation. The vertical distribution of the tomato borer shows that the dispersal of
the populations begins only in the third generation which is preferentially situated in the
average (median) and high part of the plantations. From the 7th week after the beginning of
the try, we note a population more raised on the median part where all the préimaginaux
stages are represented. During the weeks 8, 9 and 10, the number of eggs remains high and
that of the young stages (L1 and L2) is raised but stable rest. In the end of the week 10 (that is
more than 2 and a half months after the infestation) the population at the level of this stratum
(N2) is 135 individuals, but on the high part the population increases appreciably from the
week 7 to reach 350 individuals at the end of the SEM 12; Let be 3 months after the beginning
of the infestation.
A work in the laboratory on the food preferences of the various stages of development of
the predator Nesidiocoris tenuis Reuter (Hemiptera: Miridae) with regard to the various
instars of T. absoluta revealed that all the instars of the predator feed on eggs and on larvae of
the tomato leafminer; however there is a preference marked for eggs with a 98, 3 % rate, for
young larvae (L1) this rate is 92, 7 %. For the larvae of the 2nd instars (L2) are 65, 5 %. The
older larvae (L3) are 13, 8 % and 6, 6 % for the instars L4. On the other hand nymphs are not
consumed.
I f the predator consumes a large number of eggs and the young larvae, there is a high
chance for the tomato leafminer does not cause too many damages on the culture, especially
under greenhouse. From these data, we can choose the moment of the releases of N. tenuis to
have a better efficiency of fight against T. absoluta.
