ABSTRACT
In order to select an isolate of Metarhizium anisopliae promising for the microbial control of Tibraca limbativentris and to evaluate its virulence in all stages of development of this insect, two bioassays were carried out. Five isolates of M. anisopliae were applied using fungal suspension with 108 conidia/mL, in the following treatments: 1) control, 2) isolate CG 041, 3) CG 144, 4) CG 167, 5) CG 835 and 6) CG 891. To evaluate the virulence in the stages of development, a suspension with 108 conidia/mL from the isolate CG 891 was prepared and applied over the eggs, small nymphs (2nd and 3rd instars), large nymphs (4th and 5th instars) and adults. In the first experiment, the calculated TL50 values showed that the isolate CG 891 was the most virulent, and about 11 days were necessary to control 50% of the tested population. In the second experiment, designed for eggs, the TL50 value was 5.53 days, when 83% of contamination was observed, and none of the hatched nymphs reached the second instar. In the other treatments, the TL50 values were 6.61, 8.76 and 8.82 days for small nymphs, large nymphs and adults. Eggs, nymphs and adults of T. limbativentris were susceptible to M. anisopliae (isolate CG 891).
KEY WORDS
Insecta; rice stem bug; entomopathogenic fungus; irrigated rice