The efficacy of Steinernema feltiae in the control of Cydia pomonella in organic apple and pear orchards of Patagonia Argentina and its impact on local populations of entomopathogenic nematodes

This study evaluates the efficacy of the commercial product, Steinernema feltiae (NEMAPOM, e-nema GmbH, Germany), in controlling diapausing Cydia pomonella (Linneaus) (Lepidoptera: Tortricidae) (codling moth; CM) larvae in commercial organic orchards of pome fruits and in harvest bins in Rio Negro Valley, Argentina, subject to the attack of this pest. The infectivity of S. feltiae at different temperatures in the laboratory and the persistence in the field of this commercial product and of local entomopathogenic nematode (EPN) strains after application were determined. The field assay was carried out in winter, with an application dose of 1.5 billion infective juveniles (IJs) ha⁻¹ on a total surface of 0.5 ha. Mortality by S. feltiae in CM larvae was greater than 85% at two of the four test sites. Laboratory assays at 4 °C demonstrated its infectivity at this temperature, similar to field conditions at the times of release. In harvest bins, S. feltiae produced 10.58% and 60.37% mortality in sentinel traps at 100 and 200 IJs ml⁻¹, respectively. A local EPN, identified as Heterorhabditis bacteriophora, was detected in soil samples pre- and post-application (180 days) at all sites. S. feltiae failed to establish itself in the field and was found 24 h after application at only two sites in 20% and 80% of the samples taken (plots treated). Treatment with S. feltiae seems not to affect the occurrence of H. bacteriophora. S. feltiae was effective in controlling CM, given the environmental conditions of low temperatures and humidity in this fruit-growing region.