Efficacy and environmental impact of entomopathogenic nematodes used against nut insect pests in some chestnut woods on Etna (Italy)

Investigations were carried out to test the possibility of controlling the main chestnut fruit insect pests (tortricid caterpillars and curculionid larvae) on Mount Etna (Italy) by means of entomopathogenic nematodes (EPN) belonging to the genera Steinernema and Heterorhabditis. A survey of autochthonous EPN species, which should more suitable to be used locally, was conducted in many chestnut groves of Etna and various populations of nematodes, mainly belonging to Steinernema, were found. Laboratory tests were made to evaluate the ability of several EPN species and strains to parasitize larvae: most EPN species were shown to be effective against most insect larvae extracted from the nuts. In particular, H. bacteriophora showed a great efficacy both against the tortricids and curculionids. Soil insemination with different EPN species was made to test their persistence ability in the soil. The most persistent species was H. bacteriophora, which was found in the soil for many months after the soil insemination, that is for a time sufficient to let these nematodes find and kill the insect larvae in the soil. The environmental impact of the EPN insemination on the soil fauna was also thoroughly studied and no significant differences were found in the soil fauna composition before and after the treatment.