Phosphine resistance status in lesser grain borer Rhyzopertha dominica (Fab.) (Coleoptera: Bostrichidae) strains originating from the tropical countries

Abstract

Stored product beetles that are resistant to the fumigant phosphine (hydrogen phosphide) have been reported for more than 50 years in many places worldwide. The high levels of phosphine resistance in lesser grain borer Rhyzopertha dominica (F.) have been noted from several countries including Bangladesh. This study was designed to evaluate the status of resistance to phosphine in Bangladeshi R. dominica and to verify the possible comparison among other phosphine resistant strains from tropical countries viz. Burkina Faso and Malaysia. The data reported and summarized here showed varied levels of resistance compared to the laboratory phosphine susceptible strain (RDLAB). Rhyzopertha dominic/i>a strains originating from Bangladesh (RDBGD) and Burkina Faso (RDBKF) exhibited higher levels of resistance to phosphine compared to the Malaysian strains (RDMAL). Analysis of dose–response data indicated that the RDBGD and RDBKF strains were the most resistant to phosphine under different exposure periods. At LC50, these two strains were more than 80-fold more resistant at all exposures compared to the susceptible strain. Results also revealed that RDBGD and RDBKF strains required a relatively high concentration of 334.94 and 240.081 mg L-1 for 99% mortality. The mean survival time (MST) for the phosphine resistant and susceptible also varied significantly. The maximum MST was recorded for RDBGD and RDBKF strains. The present findings further confirmed that the Bangladeshi originated R. dominica strain contained higher resistance to phosphine compared to strains from other countries. This study could be useful in developing management strategies to prevent stored grain from being infested by resistant strains of R. dominica in tropical countries.

Keywords

• phosphine
• resistance
• grain borer
• tropical countries