Abstract

The persistence and insecticidal activity of a commercial biological insecticide Spinosad, based on fermentation product of Actinomycetales bacterium, Saccharopolyspora spinosa (Actinomycetales: Actinomycetaceae) and two plant extracts, namely Neem (Azadirchta indica) and Kanair (Nerium oleander) were evaluated against Tribolium castaneum (Hbst) on stored wheat grains. Five concentrations, namely  0.5, 1.0, 1.5, 2.0 and 2.5% of each insecticide were used at different exposure times, that is, 24, 48, 72 and 168 h. Filter paper dip method was used. Results revealed that Spinosad (Tracer 240 SC) was the best against target pest, with maximum mortality, that is, 55% at 2.5% dose in 168 h exposure time and minimum 16.66% with 0.5% concentration at 24 h exposure time. Neem showed 45% mortality at 168 h exposure time with 2.5% concentration and 16.67% at 0.5% dose at 24 h exposure time followed by Kanair with 38% mortality at maximum application rate and exposure time, that is, 2.5% and 168 h and minimum 15% at minimum application rate, that is, 0.5% at 24 h exposure time. LC₅₀ values were also calculated using Probit analysis technique. LC₅₀ values of Neem, Knair and Spinosad after 24, 48, 72 and 168 h interval were determined. LT₅₀ values of these bioinsecticides interval were also calculated at 2.5% concentration. Results revealed that bio-pesticides are better ways to manage Red flour beetle infestation in stored wheat grains.

Key words: Tribolium castaneum, Spinosad, Azadirchta indica, Nerium oleander, efficacy, LC₅₀ and LT₅₀