Efeitos de Beauveria bassiana (Bals.) Vuill. e Metarhizium anisopliae (Metsch.) Sorok. sobre parâmetros biológicos e fisiológicos de Diatraea saccharalis F.(Lepidoptera : Crambidae)

Abstract

The sugarcane borer Diatraea saccharalis F. is considered one of the main pests in America, being responsible for direct and indirect damages to this culture. The use of entomophatogenic fungi for the control of pests has been a lot intensified in the last decades, and the fungi Beauveria bassiana (Bals.) Vuill. and Metarhizim anisopliae (Metch.) Sorok were the most used. The objective of this research was to analyze the effects of these fungi, in different concentrations, on biological parameters of D. saccharalis and to analyze morphologically and quantitatively the types of hemocytes of that insect, on larvae of the 3th instar, challenged immunologically by the studied fungi, in different concentrations. It was analyzed period and viability larval and pupal, fecundity, viability of eggs and longevity of males and females of D. saccharalis, being sprayed concentrations of 103, 104, 105 conidia mL-1 on larvae. In relation to B. bassiana, the results showed that there was no difference for the larval and pupal period and pupal viability. The larval viability was reduced in the concentration of 105 conidia mL-1(56.6%). the fecundity, the viability of eggs and the longevity of males and females were affected, mainly in the concentration 105 conidia mL-1, where they presented averages of 237 eggs, 48.60%, 2.17 and 2.50 days, respectively. For M. anisopliae differences were observed in relation larval viability (56.67%), pupal period (7.86 days)pupal viability (53.33%), viability of eggs (52.34%) and longevity of males and females (2.17 and 2.50 days), in the concentration 105 conidia mL-1. The results relating to the analysis of the hemocytes revealed that the most frequent cells were the spherulocytes, plasmatocytes and granulocytes, with rates of 34.75%, 29.66% and 22.16%, respectively, while the least frequent hemocytes were the prohemocytes (8.33%), adipohemocytes (2.58%) and oenocytoids (2.41%). After inoculation with the fungus B. bassiana it was verified that differences happened only to the granulocytes in the concentration of 107 conídios mL-1 (24 and 36h) and to the plasmatocytes in the concentrations 105 conidia mL-1 (60h) and 107 conidia mL-1 (24 and 36h), where there was an increase of the granulocytes and a decrease of the plamatocytes in the largest concentration, and an increase of the plasmatocytes in the concentration 105 conidia/mL-1. M. anisopliae didn't interfere in the granulocytes and plasmatocytes. Relating to the spherulocytes a larger tendency to reduction of those cells was verified at an interval of 36h for both fungi. However a signicant difference only happened in the concentration of 105 conidia/mL-1 at an interval of 60h resulting in the smallest average for that type of hemocyte when challenged by the M. anisopliae. The obtained results indicated that B. bassiana and M. anisopliae, even being used in low concentrations, they have potential to be used in programs of control, considering that the same ones affected negatively indispensable biological parameters to the cycle of D. saccharalis.