Heterorhabditis indica and Steinernema siamkayai in central Thailand and their potential for controlling Aedes aegypti larvae in artificial container-breeding site

Abstract

Entomopathogenic nematodes (EPNs) have been extensively researched as biocontrol agents because of their effectiveness against various insect pests, including Aedes aegypti larvae, which are significant vectors of several serious diseases. While the efficacy of EPNs in killing mosquito larvae has been evaluated in laboratory settings, there are limited studies focusing on mosquito breeding containers. This study aims to isolate and identify EPN species in central Thailand and assess their effectiveness against Ae. aegypti larvae in artificial breeding sites. Forty-two isolates of EPNs were molecularly identified, revealing a close relationship to S. siamkayai and H. indica. Most EPNs were isolated from loam soils with temperatures ranging from 28–35 °C, a pH between 3.0–7.0, and soil moisture content of 1–8 %. The distribution of EPNs was linked to moisture content. All selected EPN isolates demonstrated significant mortality of Ae. aegypti larvae compared to the control, with H. indica (eCAT3.5_TH and eCNW14.5_TH) showing slightly higher efficacy than S. siamkayai (eCKP34.1_TH). The type of artificial-breeding container and water height did not significantly affect larval mortality. The highest mortality rates were recorded in ant traps, followed by vases and plastic pots. Additionally, both male and female adult EPNs were observed in larval cadavers. While melanized EPNs were found in both larval and pupal cadavers. The EPNs can grow and complete their life cycles, indicating their sustainability and efficacy for mosquito management by reducing adult emergence.