Abamectin Resistance in Tetranychus urticae Koch (Acari: Tetranychidae): Evaluation of Resistance Ratio, G326E mutation, Enzyme Activity and fitness costs

Tetranychus urticae Koch (Acari: Tetranychidae) is one of the most important pests feeding on many plants in agricultural production in the world. The aim of this study was to investigate the resistance mechanisms of the T. urticae (MER) population collected from cucumber production areas and the laboratory (GSS) population, which was used as a comparison group, against abamectin. Additionally, the study aimed to determine the effects of abamectin on the life tables of these populations. The LC50 values of GSS and MER populations were 0.0324 and 3.517 mg active ingredient per liter (mg a.i. L-1) for abamectin, respectively. The activities of detoxifying enzymes (EST, GST, and P450) in the MER population were statistically different from those in the GSS population for each of them. In order to investigate the presence of the G326E mutation in GSS and MER populations, DNA sequencing analysis revealed that none of the tested individuals exhibited this mutation associated with abamectin resistance. In addition, life table parameters were determined to identify the biological differences between the MER and GSS populations. Daily number of offspring, total number of offspring and intrinsic rate of increase (r), net reproductive rate (R0), finite rate of increase (λ) and fecundity (F) values of MER population were significantly lower than GSS population. In addition, the relative fitness value of the MER population was determined as Rf = 0.47. The findings indicate that the MER population exhibits disadvantaged reproductive characteristics compared to the GSS population. Future research should prioritize investigating the relationship between fitness costs and resistance to understand this effect better.