Evaluating the efficacy of entomopathogenic nematodes for the biological control of crop pests: A nonequilibrium approach

The efficacy of entomopathogenic nematodes for biological control is assess ed using deterministic models. Typically, the examination of such models in volves stability analyses to determine the long-term persistence of control . However, in agricultural systems, control is often needed within a single season. Hence, the transient dynamics of the systems were assessed under s pecific, shortterm control scenarios using stage-structured models. Analyse s suggest that preemptive application may be the optimum strategy if nemato de mortality rates are low; applying before pest invasion can result in gre ater control than applying afterward. In addition, repeated applications wi ll suppress a pest, providing the application rate exceeds a threshold. How ever, the period between applications affects control success, so the econo mic injury level of the crop and the life history of the pest should be eva luated before deciding the strategy. In all scenarios, the most important p arameter influencing control is the transmission rate. These findings are a pplicable to more traditional biological control agents (e.g., microparasit es and parasitoids), and we recommend the approach adopted here when consid ering their practical use. It is concluded that it is essential to consider the specific crop and pest characteristics and the definition of control s uccess before selecting the appropriate control strategy.