Storage Capacity of Entomopathogenic Nematodes in Barricade^® Gel and Potassium Polyacrylate Hydrogel

Entomopathogenic nematodes (EPNs) used as biocontrol agents are sensitive to ultraviolet (UV) light, high temperature, and desiccation. Thus, formulations have been developed to protect EPNs during application. However, the ability of these formulations to enhance storage capacity has not been investigated. This study analyzed storage capacity (survival and efficacy) of EPN species, Heterorhabditis bacteriophora (SGI 245), Steinernema tophus (ROOI 352) and Steinernema innovationi (SG I35) produced either in vivo or in vitro and formulated in 2% gel of either Barricade^® or potassium polyacrylate hydrogel (PPH). The formulations were stored at 10°C and survival of the infective juvenile nematodes (IJs) was evaluated at two-weeks intervals for eight weeks. The efficacy of formulated nematodes was evaluated using Tenebrio molitor. After two weeks, all control treatments had 0% IJ survival for all the three isolates, whereas the gel formulations exhibited 58-76% survival. The three isolates in both the Barricade^® gel and PPH formulations exhibited 37-69% IJ survival at six weeks, which declined to 0-13% after eight weeks. Both formulations of the three isolates were 60-90% effective at six weeks. The in vitro-produced IJs had a higher survival than the in vivo-produced IJs for S. innovationi and H. bacteriophora. However, the in vivo-produced IJs were more effective at killing T. molitor than the in vitro-produced EPNs for H. bacteriophora but not the Steinernema spp. In conclusion, Barricade^® and PPH gel formulations substantially increased survival of the three EPN species during storage.