Persistence of the entomopathogenic nematode Steinernema feltiae in a novel capsule formulation

• Post-application EPN efficacy is dependent on weather conditions. • EPN formulations enhance their use as biocontrol agents. • Sub-surface capsules improve EPN persistence compared to surface-applied capsules. • EPN capsules suppress pests for at least three weeks after initial application. The post-application persistence of entomopathogenic nematodes (EPNs) depends on environmental conditions, which affect their efficacy as biocontrol agents in the field. This study evaluated the persistence of the EPN Steinernema feltiae in a novel hydrogel/emulsion capsule formulation under laboratory and field conditions. The new formulation was compared to the traditional aqueous application, using the baiting method with Tenebrio molitor larvae. In laboratory experiments, the capsule formulation of S. feltiae ENO2 strain was compared with aqueous applications of ENO2 and SN strain at 23 °C for 0, 7, 14, 21, and 28 days after treatment (DAT) in soil cups. The ENO2 capsule formulation persisted longer than ENO2 aqueous, while SN aqueous also persisted better than the ENO2 aqueous application but was not different from the ENO2 treatment. In field trials, the capsule formulation (applied sub-surface) persisted longer than the aqueous application (applied on the surface) of ENO2 when applied in recommended methods; however, there were no differences between formulations when applied in-furrow (sub-surface) or on the soil surface. Comparing the application methods, the sub-surface application improved the persistence of capsules over the surface application while it did not affect the performance of the aqueous application. Overall, these findings suggest the capsule formulation buried in the soil improves EPN persistence.