Efeitos de Metarhizium anisopliae (Metsch.) Sorok. sobre a fase larval e características imunológicas de Diatraea flavipennella (Box) (Lepidoptera: Crambidae).

Abstract

Diatraea flavipennella (Box) is considered a major pest of economic importance to the culture of sugar cane in Northeast Brazil. Biological control with the fungus Metarhizium anisopliae (Metch.) Sorok., may be a viable alternative, as this pathogen is already used for other pests in this crop. This work aimed to evaluate the effects of this fungus at different concentrations, against the third instar larvae of D. flavipennella and to investigate the immune response, by analysing the types of hemocytes, and phenoloxidase, total protein and nitric oxide, tritation as well as the possible differences in the biochemical profile of hemocytes. It was observed the effect of M. anisopliae against larvae of D. flavipennella, sprayed at concentrations of 103, 104, 105 conidia/mL, which showed differences regarding to the larval period,which extended up to 72.0 days and 25.0 days in treatment the control, respectively The results for hemocytes revealed that the most common cells when sprayed at concentrations of 103, 105, 107 conidia/mL were prohemocytes, spherulocytes, plasma cells and granulocytes in relation to adipohemocytes and oenocytoids. The of nitric oxide titration was different between the control and the concentration 107 conidia/mL (24), while phenoloxidase activity was similar among treatments at 24h and was higher only at the concentration 107 conidia/mL after 60h. The total protein concentration in 107 conidia/ml (60h) was higher relatively to the control. In the biochemical profile of hemocytes there was an alteration in carbohydrates, lipids and total proteins contents at reating to the fungus. The results indicate that M. anisopliae may be used in Integrated Pest Management of D. flavipennella in northeastern sugar crops, because of the its pathogenicity and interfere with their development even when exposed to small concentrations.