Efficacy of endophytic and applied Metarhizium anisopliae (Metch.) Sorokin (Ascomycota: Hypocreales) against larvae of Plutella xylostella L. (Yponomeutidae: Lepidoptera) infesting Brassica napus plants
The
internal colonization of Brassica napus plants by Metarhizium
anisopliae was demonstrated and the endophytic and direct effects of the
fungus against Plutella xylostella larvae were assessed. Internal
colonization of the plant by the fungus was shown by re-isolating the
fungus from leaves, petioles and stems of the plant that were not the
initial site of inoculation. Results indicated that significant
differences (at P = 0.05) were obtained in mean % successful
re-isolation of the fungus from leaves, petioles and stems at 2, 3 and 4
weeks after inoculation. To assess the endophytic effect of the fungus,
larvae of P. xylostella were introduced onto plant leaves distant from
the initial site of inoculation with the fungus (one leaf per plant).
Results indicated that significant differences (at P = 0.05) were
obtained in mean % mortality of larvae that were introduced at 2, 3 and 4
weeks after inoculation compared to the non-inoculated control. Similar
significant results were obtained when the direct effect of the fungus
against the larvae was assessed. In conclusion, this research provides
evidence for the first time of the endophytic action of M. anisopliae
against P. xylostella larvae and the ability of the fungus to colonize
the internal tissues of B. napus plants.