Seleção de Metarhizium anisopliae (Metsch.) Sorok. (Deuteromycotina: hyphomycetes) para o controle de Mahanarva fimbriolata (Stal, 1854) (Hemiptera: cercopidae) da região de Mato Grosso do Sul

Abstract

The objective of this research was to select isolates of Metarhizium anisopliae (Metsch.) Sorok. Deuteromycotina: Hyphomycetes) and determine their production and viability for the control of spitlebugs Mahanarva fimbriolata (Stal, 1854) (Hemiptera: Cercopidae). The selection was carried out in laboratory conditions, using nymphs collected in the field were sprayed with the fungus and kept in an incubator at 25 ± 1 ºC, RH 70±10 and 12 h photophase. Samples of nymphs of spitlebugs were separated in groups of ten insects and inoculated in suspension of spores containing 1.0 x 109; 0.5 x 109; 1.0 x 108; 5.0 x 108 e 1.0 x 107 conidia/mL. In the stage of production the selected isolates of Metarhizium anisopliae were placed in polypropylene bags measuring 35 cm long and 22 cm wide 100 g of rice pre-cooked and immediately autoclaved at 120 °C for 25 min. After cooling, the rice was inoculated with 1 mL of a suspension containing 1,0 x 109 conidia/mL, packed an incubator at 25±1 °C, 70±10% RH and 12h photophase. Plastic bags containing rice+fungus were incubated for 10 days. After this period, rice+fungus was packed in plastic trays to promote conidia of the fungus, within the climatic chamber at 25±1 °C, 70±10% RH and 12h photophase. The trays were stacked in 4 days, crossing them for another 4 days. Was observed the total mortality, mortality corrected by Abbott's formula and confirmed mortality. Overall, it was observed that the concentration of 1.0 x 109 conidia/mL showed the greatest effect on M. fimbriolata among the other concentrations. The value of TL50 (2.75 days) provided by the concentration of 1.0 x 109 conidia/ml is lower among the other TL50 analyzed. Among the 24 isolates of M. anisopliae evaluated, seven isolates (UFGD 425, UFGD 22, PL 43, IBCB 348, UFGD 28, UFGD 05 e UFGD 03) caused the highest percentage of confirmed mortality of nymphs after the seventh day after inoculation, showing potential as control agents of spitlebugs sugarcane, killing at least 70.0% of the population. IBCB 425 isolate was the most produced conidia on rice with 1.82 x 109 conidia/g rice pre-cooked by the tray method. Regarding the viability of the isolates, the IBCB 425 also showed a higher germination of conidia, with 94.84%.