Bioinsecticidal effect of tagetes erecta (Asteraceae) on the pine sawfly zadiprion vallicola (diprionidae)

Abstract

The present study was carried out with the purpose of evaluating the bioinsecticidal effect of Tagetes erecta leaves on larvae of Zadiprion vallicola. Water, acetone and ethanol extracts of T. erecta leaves were extracted by maceration. The extracts were applied in concentrations of 250 mg/L, 500 mg/L, 750 and 1000 mg/L and distilled water used as control. Mortalities were corrected in proportion and an analysis of variance was performed. In addition, the LC50 was calculated for the various extracts obtained. There were differences in mortality in concentrations (F = 171.4, p < 0.001), between solvents (F = 1060, p < 0.001) and in their interactions (F = 7.3, p < 0.001). For the control group the mortality was null, due to the extracts; the greater mortalities were presented in applications greater than 500 mg/L. As concentrations increased, mortality marked a tendency to stabilize. Acetone and ethanolic extracts, with mortalities of 0.81 and 0.96, were highly effective compared to water extracts with a mortality of 0.64. The ethanol extracts produced an LC50 of 63.1 mg/L and the acetonic extracts of 64.5 mg/L, low concentrations compared to that produced by the water extracts of 398.1 mg/L. The effects of these extracts on the mortality of Z. vallicola are similar to those reported for the entomopathogenic fungus Metarhizium anisopliae, and therefore represent a valuable alternative for its control, especially in the case of ethanol extracts.