Acute and residual concentration-dependent toxicities of some selected insecticides to adult Bactrocera invadens Drew, Tsuruta and White (Diptera: Tephritidae)

Abstract

Background

The high yield loss reported from the infestations of fruits by Bactrocera invadens Drew, Tsuruta and White in West Africa can impact negatively on the growth of horticulture in the region. Similarly, the shortage of insecticides specifically registered for the control of this pest in Ghana makes decision by farmers on which insecticide to use against this pest uncertain and risky.

Results

The result for the acute lethal toxicity shows that the lethal concentration (LC) values of the tested insecticides are 0.59 (diazinon (Diazol)), 0.81 (chlorpyrifos (Pyrinex)), 1.21 (cypermethrin+dimethoate (Cydim super)), and 3.12 (deltamethrin (Deltapaz)) ml L⁻¹ of water. The result for the residual toxicities of three concentrations for each of the tested insecticides shows that the lethal times LT (LT₅₀ and ₉₀) for the adult B. invadens differed significantly for all the ages of the residues. Some insecticides exhibited low lethal time even on panels that are up to 6 days old after treatment.

Conclusion

We concluded that the acute lethal toxicity of the insecticides from most-to-least toxic are diazinon (Diazol) > chlorpyrifos (Pyrinex) > cypermethrin + dimethoate (Cydim super) > deltamethrin (Deltapaz). The residual toxicity of the label rates of all the insecticides are equal to those of the higher doses but better than those of the least doses. The implication of these findings for the management of B. invadens has been discussed.