NATIVE LARVAL PARASITOIDS ASSOCIATED WITH TUTA ABSOLUTA (MEYRICK) IN GREENHOUSE TOMATO CROPS OF SOUTHERN SARDINIA.

: Since its first detection in Sardinia (Italy), Tuta absoluta (Meyrick) has been reported as a major pest of greenhouse tomatoes. In recent years, however, a tendency toward a progressive reduction of tomato borer infestation levels has been observed. The reasons behind this decline are probably diverse, including both the increase in growers' ability to manage the pest and the adaptation of native predators and parasitoids to the new prey/host. In order to assess the species composition of the parasitoid complex associated with T. absoluta larvae in Sardinian greenhouse tomatoes, a two-year (2010/11) survey was conducted in one of the island's major horticultural areas (Pula, Cagliari). An estimate of the levels of parasitism caused by native wasps was also carried out. The occurrence of larval parasitoids of T. absoluta was detected in approximately half of the crops monitored. The average parasitism rate recorded in tomato plants infested by tomato borer larvae was 1.3%. Moreover, while no parasitism was observed in 76.4% of the samples collected, only 3.0% of the samples showed a parasitism rate exceeding 10%. The highest rates were recorded in spring and summer, with a peak in July (4.8%). Of 159 adult parasitoids recovered from infested leaves, 62.9% were found to belong to a Necremnus sp. near artynes (Walker), 34.6% to a Necremnus sp. near tidius (Walker), and 2.5% to Neochrysocharis formosa (Westwood) (Hymenoptera: Eulophidae). These results show that some native parasitoids have adapted to T. absoluta in the study area. Although parasitoid abundance in tomato crops appeared to be low, their contribution for the control of tomato borer infestation could possibly be enhanced through the application of conservation biological control measures.