Biological control of spittlebug (Mahanarva andigena) in sugarcane (Saccharum officinarum) with Metarhizium sp. (Fungi: Ascomycota: Clavicipitaceae)

Abstract

The use of chemical insecticides causes damage to the environment and human health, so as an alternative this study characterized and evaluated native fungal strains for biological control of spittlebug, the homopteran Mahanarva andigena in sugarcane, Saccharum officinarum. The strains of the native entomopathogen Metarhizium sp. were obtained from three sugarcane-growing sectors of canton Pastaza, and were grown in two culture media, Potato Dextrose Agar (PDA) and Sabouraud Dextrose Agar (SDA) with 10 repetitions. The C1 strain from the Las Americas sector grew the fastest, reaching 7,80 and 8,00 cm diameter in the Petri dishes at 624 hours following inoculation. Morphocultural differences exhibited between strains of the entomopathogen are attributed to the culture media and probably indicate the existence of different species of Metarhizium. The C1 strain was applied to 795 sugar cane plants infested with spittlebug in a completely randomized design with 5 replicates, and the biological effectiveness of the strain in the field was determined with three different titrations: 2,8x10 ⁷ , 4,8x10 ⁷ and 1,1x10⁸ conidio/ml. The best results were obtained with the titration of 1,1x10⁸ conidio/ml, resulting in an effectiveness of 90,95% with two doses of application at an 8-day interval. We suggest that the Metarhizium strain that originated in the area of Las Americas, which is held in the entomopathogenic collection at the Universidad Estatal Amazónica, be used as a biocontrol of M. andigena, a pest which causes great economic losses in the agricultural and agroindustrial sectors of the region.