Temperature-induced effects on development, reproduction, and predation of Harmonia axyridis fed on first instar larvae Spodoptera litura.

Abstract

Since metabolism, survival, and reproduction in hexapods are closely related to temperatures; changes in the mean and variance of temperature are major aspects of global climate change. In the typical context of biological control, understanding how predator-prey systems are impacted under thermal conditions can make pest control more effective and resilient. With this view, this study investigated temperature-mediated development and predation parameters of the predator Harmonia axyridis against the potential prey Spodoptera litura. The age-stage, two-sex life table of the predator was constructed at four temperatures (i.e. 15, 20, 25, and 30°C) by feeding on the first instar larvae of S. litura. Our results showed that the mean generation time (T) decreased but the intrinsic rate of increase (r) and the finite rate of increase (λ) increased with increased temperature. The mean duration of the total preadult stage decreased with higher temperatures. The T and r were 70.47 d and 0.0769 d^-1 at 15°C; 58.41 d and 0.0958 d^-1 at 20°C; 38.71 d and 0.1526 d^-1 at 25°C; and 29.59 d and 0.1822 d^-1 at 30°C, respectively. The highest net reproductive rate (R₀) and fecundity were obtained at 25°C. The highest λ (1.1998 d^-1) and lowest T (29.59 d) were obtained at 30°C, whereas the maximum net predation rate (C₀) was at 25°C. Total population and predation rates projections were the highest at 30°C. Based on these findings, we anticipate that biological control strategies for this predator release against S. litura should be attuned to warming scenarios to achieve better biocontrol functions.