Evaluation of Steinernema carpocapsae survival and infectivity after cryopreservation

A cryopreservation protocol, with an optimum survival rate of 86.8 %, was developed for a strain of Steinernema carpocapsae (Weiser) ItSCAO1 isolated in a lagoon plain in Veneto Region (northern Italy). Some laboratory bioassays were carried out against Galleria mellonella (L.) (Lepidoptera: Pyralidae) larvae to determine the infectivity and stability of this strain after cryopreservation. Insect mortality was very high in different assays (sand column and penetration assays), while the percentage of penetrating infective juveniles was 59.4 and 33.8 respectively. Larval mortality in a one-on-one quality assay was 66.6 % while in an exposure time assay the exposure time to nematodes required to achieve 50 % insect mortality was lower than 20 min. With the results of infectivity assays we can evaluate the possibility to use cryopreservation for long-term storage of entomopathogenic nematodes for biological control programs.