Abstract:

Entomopathogenic nematodes (EPNs) (Rhabditida: Heterorhabditidae and Steinernematidae) are effective biocontrol agents for many insect pests and are generally stored for a period of time prior to their use in the laboratory or field. However, unfavorable storage conditions have a great impact on the survival and infectivity of EPNs. This study was conducted to determine the optimum storage conditions of infective juveniles (IJs) of four native EPN species (Heterorhabditis bacteriophora FLH-4H, H. indica 216-H, Steinernema feltiae KCS-S, and S. bicornotum MGZ-4S) under laboratory conditions. The survival capability of the IJs was tested at different concentrations (500, 1000, 1500, and 2000 IJs), temperatures (9 and 25 °C) and storage media [double-distilled water (ddH2O), tap water, and sterile Ringer solution]. In general, the survival of IJs of tested EPN species was the highest at the 1st month after treatment (MAT) at the concentrations of 1000 and 1500 IJs and gradually decreased with the increasing storage periods. The survival rates of the IJs of Steirnematids were generally higher than Heterorhabditid species. The highest survival of IJs was generally obtained after 1-month storage in Ringer solution at 9°C while tap water led to poor survival for the IJs at both temperatures tested. The IJs that were stored at 9°C induced higher mortalities on the larvae of Galleria mellonella (L.) (Lepidoptera: Pyralidae). The results showed that the IJs of tested EPN species can remain viable for a longer period of time in Ringer solution at 1000 and 1500 IJs concentrations at 9°C without losing much of their infectivity.

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