The mite ectoparasite Varroa destructor, poses a serious threat for the survival of the Apis mellifera colonies. The intensive use of acaricidal products is one of the most common methods for defending bees from Varroa that can cause the contamination of the wax foundation used in beekeeping. The natural honeycomb management could provide a solution for this problem, because it involves the use of frames without wax foundation which allows the bees to build a complete comb ex novo. On the other hand, colonies which are free to build cells of their choice, usually build a number of drone cells higher than colonies managed with the wax foundation. This could potentially lead to several negative consequences because the V. destructor reproductive success is greater on drone broods than on worker broods. The aim of the present study was to examine the colony development, to evaluate the honey production and to monitor the growth of V. destructor infestations and associated virus infections in Apis mellifera colonies managed by using natural honeycombs compared with the conventional management. Several colony parameters were measured in spring and summer. The strength of the colony was used to estimate the worker and drone populations. In order to measure the V. destructor infestations were used several methods, such as the natural mite fall, the powdered sugar roll, the soapy water and the brood cell uncapping. Molecular analysis was performed in order to measure the viral load of five Apis mellifera viruses. The honey produced was measured by collecting the honey stored in the supers, which are boxes placed on a beehive for bees to store. The results showed that the higher presence of drone brood in the colonies managed using the natural honeycomb did not negatively affect the colony development nor the mite V. destructor population compared to control colonies. The molecular analysis showed that the DWV was the most common virus found in bee samples, and its viral load was more influenced from the mite infestation rate than from the treatment. The analysis carried out in this study showed that the natural honeycomb management can represent a valid alternative to the wax foundation. This kind of colony management thus appears to contradict our primary hypothesis which was that letting the bees build their own honeycomb would have led to a significant increase in the V. destructor infestation. Productivity data did not provide reliable results about the difference between the natural honeycomb and the conventional colony management due to climatic adversities. Further studies will be performed to better investigate this aspect. Data about the natural mite fall and the estimation of the mite population in the phoretic/reproductive phases provided a useful starting point for further studies on the correct timing to carry out acaricide treatments both in conventional and natural honeycomb managed colonies.

The brown marmorated stink bug (BMSB), Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is an invasive phytophagous species native to eastern Asia. Due to its wide host plant range, it is considered among the most harmful agricultural pests in the invaded areas, including Europe, North and South America. In addition to its impact on crops, this insect causes a nuisance in urban areas, by invading buildings for overwintering using their aggregation pheromones and emitting an unpleasant smell when disturbed. The current management of this species is mainly based on the use of chemical insecticides, which show efficacy when applied frequently, with consequent negative impact on beneficial insects in the agroecosystems. As a result, there is a desire for more environmentally friendly solutions for the management of BMSB. A valid alternative is the use of exotic and coevolved biocontrol agents, for instance, the Samurai wasp, Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae), which is already showing promising medium and long-term results against BMSB in classical biocontrol projects. Within the frame of the least-toxic alternatives, the use of the Sterile Insect Technique (SIT) in an Area-Wide management approach is potentially a valid strategy to be included in integrated control and eradication programs. The main objective of this research, therefore, was to develop a SIT for potential use in the eradication of BMSB in newly introduced areas and/or as an additional tool to reduce its impact in areas where invasive populations have been already established. However, the effective use of SIT requires producing a high number of insects, and mass rearing for such a species is considered too complicated and expensive. To overcome this limitation, we evaluated a harvest, irradiation, and release strategy using wild overwintering adults. New live traps baited with high-load pheromones have been developed for mass trapping, exploiting the natural phenomenon ruled behaviour of aggregation of BMSB in preparation for overwintering. The captures of the new pheromone traps were compared with those of identically baited sticky panels through daily services lasting 2 weeks. Following winter diapause, the collected males were irradiated with high-energy photons at four different dosages: 16, 24, 32 and 40 Gy. The effects of irradiation on the biology i.e., fertility, longevity, and mating behaviour of overwintering BMSB males were evaluated with respect to unirradiated males. To encourage the use of SIT, a linear accelerator from a hospital facility was used for irradiation instead of the classical method involving radioactive materials. A second control 0 Gy was adopted to evaluate the possible negative effects on the biology (longevity, fertility, and fecundity) of insects due to the preparation for the irradiation. Moreover, as part of an integrated pest management (IPM) strategy, the combined use of the egg parasitoid T. japonicus and SIT was considered. The suitability of sterile eggs as oviposition substrate for T. japonicus was evaluated by comparing irradiated BMSB eggs at 40 Gy, eggs obtained by fertile female mated with sterile males irradiated at 50 Gy, and refrigerated sterile eggs currently used for laboratory rearing and field monitoring. The results of the research are encouraging for SIT applications in IPM approach. 1) The new traps caught up to 15-times more adult BMSB than the sticky panels in the two weeks of collections. 2) The developed irradiation protocol that involved a 6 MV medical linear accelerator has allowed the achievement of a high level of sterility of overwintering males (over 95%) already at 32 Gy without compromising males’ longevity and mating behaviour (in no-choice conditions). No adverse effects due to the irradiation preparation protocol were observed. 3) Sterile eggs obtained by mating sterile irradiated males and fertile females (SIT eggs), showed a higher parasitoid emergence rate (%) than both those directly irradiated and refrigerated. The difference in the emergence rate is even more evident when the eggs are 20 days old, with a parasitoid emergence rate of (75.56 %) for SIT eggs compared to those irradiated (44.68 %) and refrigerated (37.57%). In conclusion: 1) the new live traps are effective in mass trapping, 2) wild harvested males of BMSB can be used in SIT, 3) the use of linear accelerators for irradiation of BMSB is a feasible alternative to classical radioactive sources and 4) sterile eggs obtained by mating sterile males and fertile females are a valid substrate for T. japonicus oviposition, supporting the potential use of SIT on BMSB.

This thesis treats mathematical models for host-parasitoid interactions. It is composed of three parts. In the first part, a class of such models is analyzed theoretically. It focuses on the phenomena of multiple coexistence equilibria of competing parasitoid species. The second part is about a model for determining how a parasitoid release should be timed to optimally control the invasive fruit fly Drosophila suzukii. The third part analyzes an experiment for releasing parasitoids in a greenhouse which is infested by D.suzukii. The models presented are used to discuss how to improve such biological control strategies.

Il sinergizzante piperonil-butossido (PBO) usato in combinazione con insetticidi è in grado di contrastare i parassiti resistenti inibendo temporaneamente i sistemi di detossificazione. Nuovi sinergizzanti sono stati sintetizzati a partire dalla struttura molecolare del PBO, ma anche gli insetti utili come le api possono risentire di una maggiore efficacia degli insetticidi. In questo studio abbiamo osservato l’attività enzimatica in vitro (esterasi, acetilcolinesterasi, glutatione S-transferasi e monossigenasi P450) di api operaie Italiane e Carniche in presenza del PBO e dei suoi nuovi derivati del benzodiossolo e 2,3-diidrobenzofurano mediante saggi spettrofotometrici, per determinare se i sistemi di detossificazione e altri sistemi enzimatici sono influenzati dai sinergizzanti. I nuovi derivati del PBO possono inibire parzialmente le esterasi in alcune popolazioni di api più sensibili. Altri sistemi enzimatici non sembrano essere inibiti dai sinergizzanti studiati. Studi di tossicità acuta orale e di contatto sono stati condotti in laboratorio presso il Bee Research Institute (Dol, Repubblica Ceca) su api operaie Carniche per verificare il possibile incremento di tossicità degli insetticidi imidacloprid e alfa-cipermetrina in combinazione con PBO e i suoi derivati del benzodiossolo. Gli studi hanno mostrato una differenza significativa tra la tossicità dei due principi attivi da soli e in combinazione con i sinergizzanti. / The synergist piperonyl-butoxide (PBO) has been proved to successfully control resistant pests when combined with insecticides by temporarily inhibiting the detoxification systems which lead to resistance. New synergists, starting from the molecular structure of PBO, have been developed but pollinators may also suffer from an increased efficacy of insecticides. In this study we observed in vitro enzyme (esterases, acetylcholinesterases, glutathione S-transferases and P450 mixed function oxidases) activity of Italian and Carniolan honey bee workers in presence of the synergist PBO and its novel benzodioxole and 2,3-dihydrobenzofuran derivatives through spectrophotometric assays, to determine if detoxification systems and other enzymatic systems are affected by synergists. This data show that novel PBO derivatives may partially inhibit esterases in some honey bee populations which are more sensitive. Other enzymatic systems seem not to be targeted by the studied synergists. Acute oral and contact toxicity studies were conducted in laboratory conditions at the Bee Research Institute (Dol, Czech Republic) on adult Carniolan workers to investigate the possible increase of imidacloprid and alpha-cypermethrin toxicity when combined with PBO and its benzodioxole derivatives. Tests showed some significant difference between the toxicity of the two active principles alone and combined with the synergists.

L’afide del pesco Myzus persicae rappresenta uno degli insetti più dannosi in agricoltura. Estremamente polifago e cosmopolita, viene combattuto principalmente con trattamenti insetticidi. Nel corso degli ultimi anni neonicotinoidi e piretroidi hanno rappresentato i componenti principali delle strategie di difesa contro questa specie, ma recenti programmi di monitoraggio condotti in Sud Europa hanno rivelato la presenza di popolazioni resistenti, mettendo in dubbio l’efficacia a lungo termine di queste classi di prodotti. Il presente lavoro prende in esame la diffusione dei principali meccanismi di resistenza agli insetticidi nelle popolazioni di M. persicae presenti sul territorio italiano. La prima parte si concentra sulle resistenze target-site e considera la distribuzione delle principali mutazioni che sono state associate alla resistenza a neonicotinoidi e piretroidi. La seconda parte riguarda le resistenze metaboliche e analizza le principali classi di enzimi associate ad attività di sequestro o detossificazione delle molecole di insetticida. Infine, il progetto si focalizza sulla caratterizzazione delle possibili interazioni tra tali enzimi detossificanti e molecole sinergizzanti quali il ben noto piperonil butossido (PBO). I risultati ottenuti consentiranno di migliorare le strategie di difesa per evitare trattamenti inefficaci e mantenere il più a lungo possibile l’efficacia dei prodotti oggi disponibili per il controllo di M. persicae. / The green peach aphid Myzus persicae is a globally significant crop pest, controlled mainly by chemical treatments. In recent years neonicotinoids and pyrethroids have been the main components of pest management strategies used by growers. However, recent monitoring programmes in Southern Europe have shown the widespread presence of resistant populations, posing a serious threat to the long-term efficacy of these insecticide classes. The present work aims to characterise the main biochemical and molecular mechanisms responsible for insecticide resistance in Italian populations of M. Persicae. The first part is focused on target-site resistance and consider the frequency and distribution of the main target-site mutations associated with neonicotinoid and pyrethroid resistance. The second part is related to metabolic resistance and analyses the involvement of detoxifying enzymes able to sequester or metabolise the insecticide molecules. Furthermore, the project aims to characterise possible interactions between those enzymes and synergistic compounds like the well-known piperonyl butoxide (PBO). Results obtained by this investigation will help to improve insecticide resistance management strategies, in order to avoid ineffective applications and maintain the long-term sustainability of chemical control against M. persicae.

Apis mellifera Linnaeus (1758) è un insetto eusociale conosciuto in tutto il mondo sia per la produzione di miele sia per il suo ruolo di impollinatore, uno dei servizi ecosistemici fondamentali per la biodiversità del pianeta. Durante la sua attività di foraggiamento, l’ape è esposta agli inquinanti ambientali tra cui il particolato atmosferico aerodisperso (PM). Il particolato atmosferico può depositarsi sul corpo dell’insetto e infine contaminare anche i prodotti apistici come polline e miele. Il PM può avere diverse dimensioni (es. PM10, PM2.5, PM0.1), composizione chimica, morfologia e fonti di emissione (naturale o antropica). Nel presente elaborato di tesi, tecniche di microscopia elettronica a scansione (SEM-EDX) sono state utilizzate per caratterizzare la contaminazione da PM di origine antropica del corpo dell’ape e dei suoi prodotti (Capitolo 2 e Capitolo 3) e analisi molecolari per studiare gli eventuali effetti sub-letali sul microbiota intestinale di api esposte ai PM per via orale (Capitolo 4). / Apis mellifera Linnaeus (1758) order Hymenoptera family Apidae, is a eusocial insect widely known for its role in pollination, a fundamental ecosystem service for plant biodiversity and ultimately for the planet. During flight and foraging activity, the honey bee can collect airborne particulate matter (PM) on their own body, especially on the forewings, and can also contaminate bee products as pollen and honey. Particulate matter can originate from natural or anthropic sources, and is characterised by size (e.g., PM10, PM2.5, PM0.1), chemical composition, and morphology. In this thesis, honey bee, pollen and honey were used as bioindicator of PM – from coarse to ultrafine – in industrial areas of the Po Valley, Italy (Chapter 2 and Chapter 3). The (sub-lethal) effects of Titanium dioxide – a widespread airborne PM1 pollutant – on the honey bee through oral exposure was then investigated (Chapter 4). The technique used to analyse the PM contaminating bees and bee products is the scanning electron microscopy (SEM) coupled with X-ray spectrometer (EDX). EDX spectra allowed us to obtain chemical information from specimens, while backscattered-electron (BSE) imaging and elemental mapping provided both compositional and topographic information of PM.