Pathogenicity and field efficacy of the entomopathogenic fungus, Lecanicillium saksenae Kushwaha, Kurihara and Sukarno in the management of rice bug, Leptocorisa acuta Thunberg

A new indigenous isolate of Lecanicillium namely L. saksenae was tested for its efficacy against rice bug. Lecanicillium lecanii was non pathogenic to rice bug. Peculiar pre mortality symptoms like ataxis, aggregation, convulsions were exhibited by test insects upon infection. L. saksenae was characterized by it's quick kill effect, causing 100 per cent mortality of adults and nymphs within 72h after treatment with high spore doses of 10⁸ and 10⁷ spores mL^-1. Furthermore, probit analysis done at 6 days of treatment, revealed the LC₅₀ as 2.99 x 10⁴ and 1.72 x 10⁴ spores mL^-1 for nymphs and adults respectively. LT₅₀ (10⁸spores mL^-1) was 17.58 and 18.58 hours for nymphs and adults respectively. Although the quick kill effect was not exhibited in field, the count of rice bugs in plots treated with oil formulated L. saksenae were significantly lower (1.33 bugs per plot). Moreover, all the bioformulations applied as treatments were evidently safe to natural enemies present in rice ecosystem. The yield recorded from plots treated with oil formulated L. saksenae was also higher (3.48 kg per plot of 2 x 2 m). This study projects the prospect of utilizing L. saksenae, and its oil formulations as an effective biocontrol agent against rice bug which is a major sucking pest of rice.