Abstract

The virulence of Beauveria bassiana to overwintering Sunn pest adults was determined in the laboratory using micro-application techniques. Five microliter of 2 × 10³, 2 × 10⁴, 2 × 10⁵, 2 × 10⁶, 1 × 10⁷, 2 × 10⁷, 1 × 10⁸ conidia/ml^-1 were used in  November, January and March. Applications were made to the mesosternum of adults. Mortality was recorded every 2 days for 16 days. Isolates were efficacious to Sunn pest at the higher concentrations. The cumulative corrected mortality after 12 days varied from 2.3% (SPT22) at 2×10³ conidia/ml^-1, when treatment was conducted in November, to 100% (SPSR2) at 1×10⁸ conidia/ml^-1 in March. The LC₅₀ for SPSR2 decreased from 1.1×10⁷ to 3.7×10³ conidia/ ml^-1 when treatment was conducted in November and March, respectively. The 50% lethal time (LT₅₀) varied from 17.07days for GHA (the commercial fungal isolate – in BotaniGard), to 9.31 days for SPSR2 in November. The most efficacious isolate was SPSR2.    

Key words: Sunn pest, Eurygaster integriceps, Beauveria bassiana, LC₅₀, LT₅₀.