Early and off-season biological control of medfly with entomopathogenic nematodes: From laboratory experiments to successful field trials

The Mediterranean fruit fly Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) is an important pest of citrus and other deciduous fruit trees. There is a need for sustainable pest management tools and the use of entomo-pathogenic nematodes have been explored for controlling the stages of medfly that occur in the soil. We have investigated further this approach by assessing the efficacy of commercially available entomopathogenic nem-atodes applied early season or off-season when the medfly populations are passing through their annual bottleneck period, aiming at reducing their population before the growing season. In laboratory experiments, the efficacy of commercial strains of Steinernema carpocapsae, Steinernema feltiae, Heterorhabditis bacteriophora and H. downesi at doses of 1.5 x 106 IJs/m2 and 2.5 x 106 IJs/m2, at 15C degrees and 25C degrees was assessed. Steinernema feltiae was found to result in up to 70 % reduction of adult medfly emergence at a dose of 2.5 x 106 IJs/m2 and lower temperatures, confirming its superiority over other commercially available species. Field trials in citrus groves in Corinthos, Greece in Spring 2021 (early season) and Autumn 2021 (off-season) showed that a single application of S. feltiae at moderate dose regimes can provide about 62-65 % suppression of adult medlfies. Therefore, a single, moderate dose application of entomopathogenic nematodes early or off-season, which is more economically feasible can provide significant suppression of overwintering medflies and can be safely integrated with other tools for medfly management.