Biological control of chestnut insect pests by means of entomopathogenic nematodes

A study was carried out on the chestnut fruit insect pests on Mount Etna (Italy) and on the possibility of controlling them by means of entomopathogenic nematodes belonging to the genera Steinernema and Heterorhabditis. The field research was conducted in two small, uncultivated chestnut groves on Etna; the most abundant insect parasite was Pammene fasciana, but a few specimens of balaninus (Curculio elephas and C. glandium) were also found. The percentage of damaged nuts was rather high, reaching in some cases 67% of the crop. A survey of autochthonous entomopathogenic nematode species, more suitable to be used in the treatments, was conducted in many chestnut groves of Etna and various populations of nematodes, mainly belonging to Steinernema, were found. Laboratory tests were made on insect larvae infestation ability by several entomopathogenic nematode species and stocks: most entomopathogenic nematode species showed to be effective against most insect larvae extracted from the nuts. In particular, H. bacteriophora showed a great efficacy both against the tortricids and balaninus. Soil insemination with different entomopathogenic nematode 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 soil insemination, i.e. for a sufficiently long period of time to permit these nematodes to find and kill the insect larvae in the soil.