The role of drought in the efficacy of some entomopathogenic nematodes

Entomopathogenic nematodes (EPNs) are endoparasitic organisms commonly used in the control of agricultural pests. There are several factors that determine the efficacy of EPNs on hosts, with one of the most significant being soil moisture. The aim of this study is to determine the effectiveness of some EPNs on hosts at different doses and under different soil moisture conditions. The study utilized 1 Hybrid Strain and 3 EPN isolates, Heterorhabditis bacteriophora Poinar, 1976 (Rhabditida: Heterorhabditidae) HBH hybrid strain, Steinernema carpocapsae Weiser, 1955 TUR-S4 isolate, and Steinernema feltiae Weiser, 1955 (Rhabditida: Steinernematidae) TUR-S3 and S-Bilecik isolates. These species were applied to Tenebrio molitor L., 1758 (Coleoptera: Tenebrionidae) larvae at 5, 10, and 15 Infective Juveniles (IJs) doses, under 1, 4, 7, 10, and 13% soil moisture conditions. The study was conducted in 2024 at Bursa Uluda & gbreve; University, Faculty of Agriculture, Department of Plant Protection, Nematology Laboratory. As a result, the highest mortality rates on T. molitor larvae were obtained at 13% soil moisture with 15 IJs, 100% for HBH, 93.33% for TUR-S4, 86.67% for TUR-S3, and 83.33% for S-Bilecik. This study carries important implications for understanding the relationship between EPN efficacy on hosts and soil moisture.