Dispersal of Steinernema scapterisci (Rhabditida: Steinernematidae) after Inoculative Applications for Mole Cricket (Orthoptera: Gryllotalpidae) Control in Pastures

The passive dispersal of Steinernema scapterisci Nguyen & Smart by its hosts was monitored and quantified after inoculative releases consisting of 1-ha applications in each of six pasture sites in Florida. Pitfall trap catches of Scapteriscus spp. mole crickets were used to determine levels of infection, dispersal of the nematode from release areas, and effects on mole cricket abundance for 2 years after the releases. The nematode was established at five of the sites and dispersed at least 150 m from release areas at three of them. Mean maximum cumulative distance dispersed (60 m) and cumulative area occupied (4.2 ha) by the nematode occurred within 21 months after application. The relationship between mean cumulative distance dispersed and time is described most accurately by the polynomial equation Y = 0.453 + 0.030X2 − 0.0002X3 where Y = mean cumulative distance dispersed (m) and X = number of weeks after treatment. Mean infection levels for mole crickets collected from within the treated area, on the edge of the treated area, and 50 and 150 m from the treated area were 14.6, 12.1, 5.0, and 2.8%, respectively. Twenty-four-hour trap catches, mole cricket tunnel estimates, and soap-flushes of mole crickets failed to reveal consistent effects of the nematode on mole cricket abundance. However, our study has shown that an entomopathogenic nematode species, in particular, S. scapterisci, can be used as a classical biological control agent. Inoculative release of this nematode is a viable alternative to inundative release for mole cricket suppression.