Investigation into the use of entomopathogenic nematodes to control banded fruit weevil (Phlyctinus callosus) in apple and pear orchards

Very little research has been done on the use of EPN for the control of the banded fruit weevil (BFW), Phlyctinus callosus. The main reasons therefore is probably their sporadic occurrence in the field and the lack of suitable techniques for rearing large numbers of high quality larvae for laboratory and field experiments. In this study an artificial medium could not be successfully developed, but a technique, using mature carrots with the lofts intact, planted in pots and inoculated with weevil egg has been used to rear weevil larvae successfully. As large numbers of adults are more readily obtainable, this technique could be refined to culture large numbers of weevil larvae for future field trials with EPN.

Different bioassays performed in the laboratory showed a definite potential use of EPN for the control of the BFW. A nematode were selected and used in all other bioassays which include: the susceptibility of weevil adults and larvae; the effectively of nematode larvae to move downwards and infect weevil larvae; lethal dose and lethal time at different concentrations; the effect of temperature and the ability of the nematode to complete their life cycle in the larvae. Persistence has been tested in a highly infected BFW field showing infection for up to 84 days.

This study should be seen as pioneers work in the use of EPN for the control of the BFW. The next step should be to refine culturing of weevil larvae to obtain high numbers to use in field trials. As this insect is very difficult to study in natural conditions, cages with larvae should be planted in the soil, nematodes applied and evaluated for infection.