Predation of Raoiella indica (Acari: Tenuipalpidae) by Stethorus tridens Gordon (Coleoptera: Coccinellidae)

Abstract

The red palm mite (RPM), Raoiella indica Hirst (Acari: Tenuipalpidae), is an invasive species in several American countries and has a wide range of hosts, causing significant damage, mainly to coconut and banana crops. Previous studies conducted in America have focused on the biological control of RPM through predatory mites and insects. Stethorus tridens Gordon (Coleoptera: Coccinellidae) is considered a promising biocontrol agent of phytophagous mites it has been observed on several cultures, and has a high predatory capacity. The aim of this study was to investigate S. tridens preferences among different developmental stages of RPM and estimating the functional and numerical responses of S. tridens over its most preferred prey-stage. Furthermore, the prey preference of S. tridents was examined between eggs of Tetranychus evansi Baker and Pritchard (its natural prey) and eggs of RPM through two-choice and non-choice experiments. The results showed that S. tridens prey on all developmental stages of RPM, with a marked preference for eggs over other stages of RPM. The functional response of this predator was type III, as consumption increased rapidly at intermediate egg densities. Predation on RPM eggs was unable to stimulate S. tridens reproduction, even at the highest densities. When we compared the food preference of S. tridens to eggs of T. evansi and RPM, we found that the predator preferred tetranychids. The results of this study suggested that RPM can be used as alternative prey to S. tridents, serving as a source of energy and allows for maintenance but not its reproduction.