Enzymes mediating resistance to chlorpyriphos in Aphis fabae (Homoptera: Aphididae)

The black bean aphid, Aphis fabae (Homoptera: Aphididae), is a widespread pest that has more than 200 hosts in the world. Insecticide resistance (IR) due to frequent applications is the major limitation in integrated pest management programs. Biochemical resistance is a common type of IR in which the insecticide is detoxified by one or more enzymes of the pest before reaching its target site. In this study, the IR of A. fabae populations to chlorpyrifos was evaluated in two single sprayed fields (fields A and C) and one replicated spraying field (field B) in comparison with a susceptible population (field H) during 2015. After treatments, total protein content and the activity of two detoxifying enzymes, esterases (ESTs) and glutathione S-transferases (GSTs), and acetylcholinesterase (AChE) in the populations were determined. Results clearly showed higher total protein content for the field populations compared to the susceptible population. The total protein content in field B population was significantly more than other populations. The total protein contents in Field A, B and C were 2.81, 2.89 and 1.06-fold more than susceptible strain, respectively. Higher actives of enzymes were observed in fields A, B, and C populations compared to the susceptible population (field H). The highest activity of GSTs and ESTs was observed in the field B population. Taken together, the present study demonstrated a significant IR to chlorpyrifos in the sprayed populations of A. fabae that can be attributed to the higher activity of their detoxification enzymes.