The efficacy of spindor dust (0.125% spinosad) in controlling the kola weevil, Balanogastris kolae (Desbr) infesting kolanuts in storage

Abstract

The efficacy of Spindor dust for the control of the kola weevil, Balanogastris kolae (Desbr.) was investigated in the laboratory at ambient temperature of 27 ±2^oC; 70±5 relative humidity and 12:12 h photoperiod. The insecticide was tested at three concentrations 2.5, 5 and 10g powder/kg of cured kolanuts. These were compared with the untreated nuts (control). Spindor dust was toxic to B. kolae, especially at 5 and 10g/kg concentrations. At 5g/kg and 10g/kg concentrations, Spindor dust caused high mortality of 93% and 100% on introduced weevils after 7 days whereas a total mortality was recorded 14 days after treatment. The level of weevil damage decreased with increase in concentration of Spindor dust. The mean number of feeding holes observed on nuts treated with 2.5g/kg, 5g/kg and 10g/kg concentration were 48.25, 17.13 and 4.55, respectively.  No significant difference was observed between values obtained for the 5g/kg and 10g/kg concentrations in terms of percentage larval mortality. Spindox applied at the three different concentrations was found no to taint the kolanuts as the taste of the nuts were not affected. Therefore, spindor is an insecticide that could be explored by farmers to control B. kolae during primary processing and in storage of kolanuts.