Predation dynamics in susceptible and resistant Eriopis connexa populations

The ladybird Eriopis connexa (Germar, 1824), a voracious aphid predator, faces challenges from insecticide applications, compromising biological control. As a result, the number of studies analysing the resistance and susceptibility of ladybirds has increased. Some studies have found that resistant populations differ in predation and foraging behaviour from susceptible ones. This study modelled the population dynamics of resistant and susceptible E. connexa preying on Aphis gossypii Glover, 1877 and Myzus persicae (Sulzer, 1776). A logistic model with density dependence and type II functional response was constructed to analyse predation dynamics, incorporating bifurcation analysis of predation parameters (attack rate and handling time) and the mortality rate of susceptible ladybirds. This model was used to simulate scenarios that included or excluded insecticide application and aphid resistance. To simulate the effects of insecticide applications, the parameters related to the aphids’ intrinsic growth rate ( r 1 and r 2 ) were changed to reflect the responses of susceptible and resistant populations. The same approach was used for the mortality rate of ladybirds ( d 2 and d 3 ). The results demonstrated that mortality, attack rate, and handling time were critical in shaping predator–prey interactions. Temporal simulations revealed fluctuating abundances, highlighting the fragility of these interactions under insecticide stress. This study contributed to understanding the ecological implications of insecticides, which disrupt natural predation dynamics, and showed how changes in the rates of behaviours can impact prey control. This research demonstrated the importance of integrated strategies that balance insecticide applications with preserving natural enemies and causing sustainable agricultural practices. • A pest-biocontrol model with insecticide-resistant and susceptible strains was constructed. • Coexistence of susceptible/resistant predators aids biocontrol under insecticide stress. • Insecticides disrupt aphid-ladybird dynamics by reducing the abundance of the biocontrol agent. • Abrupt changes might occur if parameters are near bifurcation points. • The results collectively show the importance of integrated pest management for aphids.