Digital Theses Archive


Tesi etd-03302021-123353

Type of thesis
Conservation biological control of the Olive Leaf Gall Midge, Dasineura oleae (Angelini, 1831)
Scientific disciplinary sector
Istituto di Scienze della Vita - AGROBIOSCIENCES
  • Nessuna parola chiave trovata
Exam session start date
Dasinuera oleae is a monophagous Cecidomyiid that attacks the olive tree. Its economic importance has always been considered negligible, especially in the western part of the Mediterranean area. However, outbreaks of this pest have been registered since 2007 from several countries, including most of the largest olive producers. In Italy, massive infestations have been reported from numerous regions in the central and northern parts of the country, but there was little information on the pest status, the biological control and the parasitoid involved in the control. For this reason, we firstly investigated the life cycle of this pest, the infestation dynamics and the parasitoid species involved in its control.<br>Results show that in Tuscany, D. oleae performs one main generation in spring, with a peak of adult emergence in April. Part of the population also performs a second generation in autumn, if the host plant produces new leaves. The spring generation is the most harmful, indeed the infestation rate increases significantly in olive orchards where parasitism is lacking. <br>We detected four parasitoid species that attack D. oleae: two belonging to the Platygastridae family (Platygaster demades and Platygaster oleae) and the others to the Pteromalidae family (Mesopolobus aspilus and Mesopolobus mediterraneus). <br>In second place, we wanted to evaluate the relative abundance of D. oleae parasitoids and their period of flight by monitoring the parasitoid community in the orchard, involving Malaise traps. We found Platygastridae as one of the most abundant parasitoid families, P. demades was the dominant species whereas P. oleae was quite rare. Results from Malaise trap catches also evidenced that the flight activity of P. demades is narrowed in March and April, when D. oleae eggs and young larvae are present. We also evaluated the effect of seminatural habitat (SNH) proportion around the orchards, the type of seminatural habitats, the olive orchards size (landscape factors) as well as the influence of D. oleae density and the edge effect (local factors). Our results show that a higher proportion of SNH nearby the olive orchards positively influences the overall parasitoid community as well as the abundance of P. demades. Furthermore, we performed preliminary investigations on the effect of species composition of the orchard’s adjoining vegetation on D. oleae parasitism rate. Results support the thesis that a high abundance of plant species associated with alternative hosts of D. oleae parasitoids, such as Erica spp, may have enhanced the colonization of the olive orchard by parasitoids. <br>The estimation of the parasitism rate is a key point in the definition of Integrated Pest Management practices. Traditional methods such as laboratory rearing of infested material and visual estimation of parasitism rate, suffer from several limitations. In order to overcome these shortcomings and to provide an early evaluation of the parasitism rate, we developed a PCR-based molecular method, starting from primers design. Results showed that the actual parasitism rate estimated by the PCR- based technique almost double of the parasitism rate estimated by traditional methods. In the case of second instar larvae, the parasitism rate detected by the molecular method was tenfold times the one assed by visual inspection. <br>