Efficacy of the entomopathogenic fungi Beauveria bassiana and Lecanicillium muscarium in the control of the tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

Background: Among the phytosanitary problems, affecting tomato crops in greenhouses heated by geothermal water in southern Tunisia, the tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is gaining prominence from year to year. Results: This study determined the susceptibility of eggs, second-instar larvae of T. absoluta to commercial formulations of the entomopathogenic fungi (EPF) Beauveria bassiana and Lecanicillium muscarium at different doses (10(10), 10(9), 10(8), 10(7) and 10(6) spores/ml). Pathogenicity tests were carried out under controlled laboratory conditions at 27 +/- 1 degrees C, and RH of 75 +/- 5%, showed that the three commercial formulations of B. bassiana R444 (Bb-Protec (R)), B. bassiana ATCC 74,040 (Naturalis (R)) and L. muscarium Ve6 (Mycotal (R)) were effective against eggs and second instar larvae of T. absoluta. Mortality rates of eggs and larvae were high with increasing the concentrations of the fungi. B. bassiana ATCC 74,040 was the most effective one, with an egg mortality rate of (71.42%) and larval mortality was greater than (80%), at the highest concentration of 10(10) spores/ml. The lethal concentration required to kill 50% of eggs was 1.56 x 10(8), 1.73 x 10(9) and 1.09 x 10(10) conidia/ml for B. bassiana ATCC, B. bassiana R444, and L. muscarium, respectively. After 7 days, the median lethal concentration (LC50) values against larvae were the lowest for B. bassiana ATCC with 2.63 x 10(7) and 4.76 x 10(6) conidia/ml by way 1 and way 2 treatments, respectively. Thus, these three formulations affected the emergence of pest's adults. The fungi significantly reduced pupation and adult emergence. Only 50.25, 60.15 and 69.16% of T. absoluta adults emerged in the treatments with B. bassiana ATCC, B. bassiana R444, and L. muscarium, respectively. Conclusions: Biological performances of the EPF showed the role of a biological control agent that can be played against T.absoluta within the framework of an Integrated Pest Management program.

Automated summary

This study found that B. bassiana and L. muscarium have good insecticidal effects on eggs and larvae of T. absoluta, and can be used as biological control agents in integrated pest management programs.