Drosophila (Sophophora) suzukii (Matsumura), new pest of soft fruits in Trentino (North-Italy) and in Europe

In September 2009, spotted wing drosophila (SWD), Drosophila (Sophophora) suzukii (Matsumura), was detected for the first time in Italy and Europe on raspberry (Rubus idaeus L.), highbush blueberry (Vaccinium corymbosum L.) and strawberry (Fragaria x ananassa Duch.) in several cultivated fields in Trentino (North-Italy). In 2010, an investigation was carried out with the aims to better understand the distribution of this species in the Province of Trento, to determine the hosts range (cultivated and spontaneous), to deepen the biology and behaviour of the pest and to set up a well-reasoned management plan. The results indicate that, in one year, D. suzukii colonised the whole territory. About 23,000 adults were caught from the beginning of July till the end of November in 82 apple cider vinegar traps placed in forest and cultivated sites located from 97 to 1458m a.s.l. Eggs and larvae were detected in fruits of sweet cherry, apricot, blueberry, strawberry, raspberry, blackberry, fig, wine grape and also in fruits of spontaneous hosts (Lonicera spp., wild blackberry, Sambucus nigra, Frangula alnus). Important crop losses (30-40%) were reported by Sant’Orsola local soft fruit growers association especially on highbush blueberry and blackberry. The efficacy of some insecticides was evaluated in open field trials; amongst the few chemicals registered on soft fruits in Italy, lambda-cyhalothrin gave satisfying results and a moderate effectiveness was obtained with spinosad. A spinosad-bait spray formulation (Spintor Fly®, Dow AgroSciences) was also tested and it achieved a modest efficacy. Severe damage might occur every season if insecticides and sanitation measures (removal and destruction of any overripe, rotting and infested fruit) are not applied during the ripening period. The increase in the use of pesticides might compromise the IPM on soft fruits (e.g. biological control of Tetranychus urticae on raspberry) and it is unsustainable over a long period for the negative impact on the environment. It is important to test as soon as possible alternative control methods (pheromones and other attractive substances, mass trapping, biological control methods, oviposition deterrents, physical barriers, etc.).