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 (Haldeman, 1847) (Diptera Cecidomyiidae) infesting black locusts, Robinia pseudoacacia L. (Fabaceae), was detected in Asia in 2002 and in Europe (first in Italy) in 2003. Its distribution in Europe has expanded dramatically, probably 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 northern Italy are reported here. O. robiniae can develop three to four generations per year by exploiting plants of different ages and vigor. Overwintering takes place as diapausing larvae and adults emerge in spring. Two generations are completed on mature plants where populations decline in summer. Two additional generations can develop on root suckers from midsummer onward. Pest population densities reach their highest levels in late spring. Gall midge larvae were attacked by various predators, but parasitism by the platygastrid Platygaster robiniae Buhl & Duso was particularly significant. The impact of parasitism by P. robiniae is indicated as a key factor in reducing O. robiniae population densities

Invasive leafminers on woody plants: a global review of pathways, impact, and management

Leafminers are a taxonomically diverse group of endophagous insects. A number of them are pests in forestry, horticulture and agriculture, and some of them have become important invasive species. Here, we discuss the characteristics of invasive leafminers of woody plants. We first present 12 cases of invasive leaf-mining species belonging to four different insect orders. For each of them, we briefly describe their invasion, including pathways of introduction, their impact and management methods and their ecology. We then discuss various aspects of these invasions. Leafminers are introduced to new continents and spread through various pathways such as horticultural trade and accidental transport of adults and pre-imaginal stages in containers and vehicles. They may also spread long distances with air currents. A few species have serious economic impacts as orchard pests, such as the citrus leafminer, Phyllocnistis citrella, or as pests of ornamental plants, such as the horse-chestnut leafminer, Cameraria ohridella. The ecological impact of these species should be better studied, especially those killing native trees, such as the birch leaf-mining weevil, Orchestes fagi, in Canada. Compared to other insect groups, invasive leafminers are usually recruited by a range of native parasitoids, which may or may not succeed in controlling the invasive species. Biological control by introduction of parasitoids from the native range has often been successful to control invasive leafminers. The review ends by short discussions on taxonomic issues and on the use of leafminers as models to study invasion ecology