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

Abstract: 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.) inseveral cultivated fields in Trentino (North-Italy).In 2010, an investigation was carried out with the aims to better understand the distributionof this species in the Province of Trento, to determine the hosts range (cultivated andspontaneous), to deepen the biology and behaviour of the pest and to set up a well-reasonedmanagement plan.The results indicate that, in one year, D. suzukii colonised the whole territory. About 23,000adults were caught from the beginning of July till the end of November in 82 apple cider vinegartraps placed in forest and cultivated sites located from 97 to 1458m a.s.l. Eggs and larvae weredetected in fruits of sweet cherry, apricot, blueberry, strawberry, raspberry, blackberry, fig, winegrape 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 fruitgrowers association especially on highbush blueberry and blackberry. The efficacy of someinsecticides was evaluated in open field trials; amongst the few chemicals registered on soft fruitsin Italy, lambda-cyhalothrin gave satisfying results and a moderate effectiveness was obtainedwith spinosad. A spinosad-bait spray formulation (Spintor Fly®, Dow AgroSciences) was alsotested and it achieved a modest efficacy.Severe damage might occur every season if insecticides and sanitation measures (removaland destruction of any overripe, rotting and infested fruit) are not applied during the ripeningperiod. 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 periodfor the negative impact on the environment. It is important to test as soon as possible alternativecontrol methods (pheromones and other attractive substances, mass trapping, biological controlmethods, oviposition deterrents, physical barriers, etc.).