The effect of the pathogenic fungus, Beauveria bassiana on tomato leafminer Tuta absoluta (Lep.: Gelechiidae)

Tomato leafminer, Tuta absoluta (Meyrick) (Lep.: Gelechiidae) is one of the important pests of tomato which causes heavy damage to tomatoes in the greenhouse and outdoor crops. In order to develop biological control of this pest, in the current study, the effects of Beauveria bassiana on different life stages of tomato leaf miner were evaluated in laboratory conditions. To investigate the effect of fungus on the length and survival rate of different stages of T. absoluta, the experiments were conducted in 10 treatments (control and different concentrations of fungal conidia) in three replications. The results showed that the egg stage and then the pupa are more sensitive to the fungus than the larval stages, and in different larval stages, young larvae are more sensitive to the application of the fungus than other larval stages. So the 50% lethal concentrations (LC50) of fungal conidia for different stages; egg, young larva, old larva and pupa was measured as 6×104, 1.16×106, 2×53.108 and 3.39 ×105 respectively. Also, the length of the larval and pupal periods of T. absoluta was affected by the application of B. bassiana, so that the length of the larval and pupal periods decreased from 51.31 to 44.12 days and from 6.64 to 5.33 days, respectively, by an increase in the concentration of fungal conidia. The results obtained in the investigation of the effect of B. bassiana on the mortality rate of different stages of T. absoluta showed that the mortality rate of all the different stages increased with the increase in the fungal conidia concentrations, so that at a concentration of 1010 conidia, the mortality rate of the different stages; egg, young larvae, old larvae, and pupae reached 89.65, 88.46, 60.71 and 90%, respectively. It was also found that by increasing the concentrations of fungal conidia, the survival rate decreased by passing of time in all stages of T. absoluta, and the survival rate increased with increasing age of larvae.