Seasonal Abundance of the Nearctic Gall Midge Obolodiplosis robiniae in Italy and the Impact of Its Antagonist Platygaster robiniae on Pest Populations

The Nearctic gall midge Obolodiplosis robiniae (Diptera Cecidomyiidae) infesting Robinia pseudoacacia was detected in Asia in 2002 and in Europe in 2003. Its distribution in Europe has been favored by extensive distribution of its host plant along the main routes. The results of a 3-yr study on the seasonal abundance of O. robiniae in Italy are reported. O. robiniae can complete 3-4 generations per year. Overwintering takes place as diapausing larvae. Two generations are completed on mature plants in spring and two additional generations can develop on root suckers in summer. Population densities can reach high levels in late spring. Parasitism by the platygastrid Platygaster robiniae is particularly significant and contributes to maintain pest densities at acceptable levels.