Monitoring of the exotic fly Drosophila suzukii in stone, pome and soft fruit orchards in NW Italy

Abstract

After its introduction in Europe, Drosophila suzukii Matsumura (Diptera: Drosophilidae), an invasive pest native to South-East Asia, has rapidly spread into many European countries, including Italy, causing several economic losses on stone fruits and berries. Therefore, monitoring of fly adults and fruit damage was carried out in stone, pome and soft fruit orchards in two areas in NW Italy in 2011–2012. In 2012, different types of vinegars and traps [apple cider vinegar (ACV), mixture of wine vinegar and ACV, rice vinegar in transparent traps; ACV in red traps] were also used in the field; moreover, the responses of females to these vinegars were evaluated in the laboratory through a two-choice olfactometer. In the two-year field surveys, adults of D. suzukii were trapped in all orchards. In both years, after few specimens were caught in early spring, adults were no longer found until June. The captures increased in late summer, reaching higher peaks in October and November. In winter, the population decreased severely, but a few adults were still caught. At harvest, no damage was found on stone and pome fruits. Instead, severe yield losses occurred on berries, especially on later cultivars. In the field, the numbers of adults sampled by the tested vinegars fluctuated highly during the season, but significant differences were found only between red traps and the other ones. In the laboratory, ACV was the most attractive substance for fly females in the two-choice olfactometer.