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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
321

Bee Shadow Recognition in Video Analysis of Omnidirectional Bee Traffic

Alavala, Laasya 01 August 2019 (has links)
Over a decade ago, beekeepers noticed that the bees were dying or disappearing without any prior health disorder. Colony Collapse Disorder (CCD) has been a major threat to bee colonies around the world which affects vital human crop pollination. Possible instigators of CCD include viral and fungal diseases, decreased genetic diversity, pesticides and a variety of other factors. The interaction among any of these potential facets may be resulting in immunity loss for honey bees and the increased likelihood of collapse. It is essential to rescue honey bees and improve the health of bee colony. Monitoring the traffic of bees helps to track the status of hive remotely. An Electronic beehive monitoring system extracts video, audio and temperature data without causing any interruption to the bee hives. This data could provide vital information on colony behavior and health. This research uses Artificial Intelligence and Computer Vision methodologies to develop and analyze technologies to monitor omnidirectional bee traffic of hives without disrupting the colony. Bee traffic means the number of bees moving in a given area in front of the hive over a given period of time. Forager traffic is the number of bees coming in and/or leaving the hive over a time. Forager traffic is a significant component in monitoring food availability and demand, colony age structure, impacts of pests and diseases, etc on hives. The goal of this research is to estimate and keep track of bee traffic by eliminating unnecessary information from video samples.
322

Molekularne osnove odgovora medonosne pčele (Apis mellifera, L.) nastres izazvan jonima teških metala / Molecular basis of honey bee (Apis mellifera, L.) response to heavy metal stress

Nikolić Tatjana 07 July 2017 (has links)
<p>Istraživanja&nbsp; u&nbsp; ovoj&nbsp; doktorskoj&nbsp; disertaciji&nbsp; su&nbsp; bila&nbsp; usmerena&nbsp; ka&nbsp; razumevanju<br />molekularnih&nbsp; mehanizama&nbsp; koji&nbsp; se&nbsp; aktiviraju&nbsp; kod medonosne pčele (<em>Apis mellifera, L</em>.)&nbsp; kao&nbsp; odgovor&nbsp; na&nbsp; stres&nbsp; izazvan&nbsp; jonima&nbsp; te&scaron;kih&nbsp; metala,&nbsp; &scaron;to&nbsp; zbog važnosti medonosne pčele kao opra&scaron;ivača&nbsp; ima&nbsp; poseban&nbsp; značaj&nbsp; i&nbsp; očekuje&nbsp; se da će doprineti očuvanju ove vrste. Istraživanja su bila podeljena u tri faze. U prvoj fazi za analize&nbsp; su&nbsp; kori&scaron;ćene populacije pčela sa lokaliteta sa različitim&nbsp; antropolo&scaron;kim uticajem&nbsp; i izmerena je koncentracija metala u pčelama, pergi i medu, kao i relativna genska ekspresija i aktivnost antioksidativnih enzima. U drugoj fazi&nbsp; pčele&nbsp; su&nbsp; u kontrolisanim laboratorijskim uslovima bile&nbsp; izložene subletalnim dozama jona te&scaron;kih&nbsp;metala&nbsp; (bakra,&nbsp; kadmijuma i olova), nakon čega&nbsp; su&nbsp; izmereni parametri koji ukazuju na redoks status i nivo oksidativnog stresa. Rezultati prve dve faze su pokazali&nbsp; da se ekspresija gena i aktivnost antioksidativnih enzima (superoksid dismutaze, katalaze i glutation&nbsp;<em> S</em>-transferaze)&nbsp; razlikuje u zavisnosti od stepena urbanizacije i industrijalizacije, dok je izlaganje bakru i kadmijumu u kontrolisanim uslovima u trajanju od 48 h dovelo samo do promene&nbsp; u ekspresiji gena&nbsp; i u većini slučajeva ekspresija je bila dozno zavisna od koncentracije metala.&nbsp; Olovo je uzrokovalo promene u koncentraciji glutationa i sulfhidrilnih grupa proteina, &scaron;to govori o tome da helacija olova može da bude prvi mehanizam odbrane od toksičnih efekata ovog metala.&nbsp; U trećoj fazi bioinformatičkom analizom je&nbsp; pronađen metalotionein medonosne pčele i ispitana je njegova funkcija u za&scaron;titi od toksičnih efekata jona te&scaron;kih metala.&nbsp; Utvrđeno je da pčele poseduju jedan&nbsp;gen za metalotionein, koji kodira mali protein sa regionima bogatim cisteinom za koje mogu da se vežu joni metala. Indukcija genske ekspresije metalotioneina medonosne pčele nakon izlaganja metalima i povećana tolerancija bakterija koje ekspresuju rekombinantni metalotionein na metale je potvrdila da metalotionein medonosne pčele ima ulogu u homeostazi bioelemenata i detoksikaciji potencijalno toksičnih metala.&nbsp; Dobijeni rezultati predstavljaju osnovu za buduća istraživanja uticaja&nbsp; jona te&scaron;kih metala na medonosnu pčelu i predstavljaju važan korak u sveobuhvatnoj proceni uticaja stresogenih faktora iz životne sredine na pčele.</p> / <p>Research in this doctoral thesis&nbsp; focuses&nbsp; on&nbsp; understanding the molecular mechanisms activated in the honey bee (Apis mellifera L.) as a response to stress caused by exposure to heavy metal ions. Because of the importance of honeybees as pollinators, this has special significance and is expected to contribute to the&nbsp; conservation of this species. Studies have been divided into three phases. In the first phase, bee populations from&nbsp; three localities under&nbsp; different anthropological influence were used and the concentrations of metals in the bees, honey and bee bread&nbsp; (perga), as well as relative gene expression and activity of antioxidant enzymes were measured. In the second phase, bees&nbsp; were exposed to sublethal doses of heavy metal ions (copper, cadmium and lead) under controlled laboratory conditions, after which parameters that indicate redox status and oxidative stress were determined. The results of the first two phases showed that&nbsp; gene expression and activity of antioxidant enzymes (superoxide dismutase, catalase, and glutathione&nbsp; S-transferase) varies depending on the degree of urbanization and industrialization, while exposure to copper and cadmium in controlled conditions for 48 h&nbsp; resulted only in a change in gene expression in the majority of cases, and the expression was dose-dependent on the concentration of the metal. Lead has caused changes in the concentration of glutathione and sulfhydryl groups of proteins, which indicates&nbsp; that chelation may be the first defense mechanism against&nbsp; the&nbsp; toxic effects of this metal. In the third stage, honeybee metallothionein was identified by bioinformatic analysis and its function in&nbsp; protection against the toxic effects of heavy metal ions was examined. It has been found that&nbsp; honeybees have one metallothionein gene, which encodes a small protein with cysteine-rich regions that may bind metal ions. The induction of metallothionein gene expression after exposure of honeybees to metals and increased tolerance of bacteria that express recombinant metallothionein confirmed that this protein plays a role in the homeostasis of bioelements and detoxification of potentially toxic metals. These results form the basis for future research on the impact of&nbsp; heavy metal pollution on the honey bee and represent an important step in the comprehensive assessment of the impact of stress factors from the environment on honey bees.</p>
323

Complementary sex determination in a solitary bee : Mapping candidate sex determination loci and associated genes

Magnusson, Sara January 2022 (has links)
The molecular mechanism of complementary sex determination in the haplodiploid organisms is poorly understood and has only been described in the honeybee Apis mellifera. In the haplodiploid system, males develop from unfertilized eggs and females from fertilized eggs. However, in some rare cases, diploid males develop from fertilized eggs. They can be distinguished from diploid and haploid males at the molecular level since they are heterozygous like females but are homozygous, like haploid males, at the sex determination locus. In this project, Osmia bicornis was chosen as the model organism, and the aim is to identify the complementary sex determination locus which should be homozygous in all diploid males. Bee nests were collected from the bees' natural habitat, and potential diploid males were identified. Data analysis of whole-genome sequencing on 17 potential diploid males was performed, which identified 80 candidate sex determination loci with 259 genes. Homologs of the Csd gene in A. mellifera were identified but not found in any candidate complementary sex determination loci.
324

Conserving urban pollinators: Local and landscape drivers of urban bee biodiversity, fitness, and trophic interactions

Turo, Katherine J. January 2021 (has links)
No description available.
325

Complementary Floral Resources for Honey Bees in a Midwestern Agroecosystem

McMinn-Sauder, Harper Bronwen Gilpin January 2022 (has links)
No description available.
326

Pollination biology of <i>Echinacea angustifolia</i> and <i>E. purpurea</i> (<i>Asteraceae</i>) in Saskatchewan

Wist, Tyler Jonathan 28 October 2005
The goals of this research project were to identify the various insects observed to visit inflorescences of Echinacea angustifolia DC, and to rank these visitors according to their importance as pollinators of E. angustifolia in Saskatchewan. Studying nectar and the nectary is essential to understanding the interaction of disc florets with pollinators. Nectar-sugar production by disc florets of E. angustifolia and E. purpurea (L. Moench) was quantified from anthesis to cessation with production per disc floret peaking in the afternoon of the staminate phase (191.7 µg) and at midday of the first day of the pistillate phase (156.6 µg), respectively. Morphology of the disc-like floral nectaries of both Echinacea species was studied, as well as the ultrastructure of the nectary of E. purpurea. Modified stomata on the nectary rim are the most likely exits for nectar, but creases in the epidermis may also participate. The nectary of E. purpurea is vascularized by phloem alone, which occurred adjacent to the epidermis. Companion cells possessed wall ingrowths, and these cells may unload arriving sugar destined for either an apoplastic or symplastic pathway. Lobed nuclei were a key feature of secretory parenchyma cells, as was a predominance of mitochondria, suggesting that energy-requiring eccrine secretion predominates in E. purpurea. E. angustifolia exhibited a generalist pollination system, with pollinating insects belonging to the orders Coleoptera, Diptera, Hymenoptera, and Lepidoptera. The pollination efficiency of visitors was determined by single insect visits to bagged, virgin inflorescences followed by quantifying pollen tubes at the bases of receptive styles and/or calculating the percentage of shrivelled styles. It was determined that bumble bees (Bombus spp.) were efficient pollinators, indicating that they would likely contribute much to the pollination of E. angustifolia. Grasshopper bee flies (Systoechus vulgaris Loew) were plentiful but individually were not efficient pollinators, but taken together, they provided much pollination. Golden blister beetles (Epicauta ferruginea Say) were efficient pollinators but where yellow-petalled flowers occurred, their numbers on E. angustifolia decreased. Honey bees (Apis mellifera L.) were efficient pollinators and were present in low numbers without managed introduction. Pierid (2003) butterflies were regular visitors and efficient pollinators, and likely contributed significantly to E. angustifolia pollination. When introduced, the alfalfa leafcutter bee (Megachile rotundata Fabr.) preferred not to forage on E. angustifolia and as such, these solitary bees were not suitable as managed pollinators. In large agricultural plantings of E. angustifolia, however, native insects may not be capable of providing sufficient pollination for seed production when floral competition occurs.
327

Pollination biology of <i>Echinacea angustifolia</i> and <i>E. purpurea</i> (<i>Asteraceae</i>) in Saskatchewan

Wist, Tyler Jonathan 28 October 2005 (has links)
The goals of this research project were to identify the various insects observed to visit inflorescences of Echinacea angustifolia DC, and to rank these visitors according to their importance as pollinators of E. angustifolia in Saskatchewan. Studying nectar and the nectary is essential to understanding the interaction of disc florets with pollinators. Nectar-sugar production by disc florets of E. angustifolia and E. purpurea (L. Moench) was quantified from anthesis to cessation with production per disc floret peaking in the afternoon of the staminate phase (191.7 µg) and at midday of the first day of the pistillate phase (156.6 µg), respectively. Morphology of the disc-like floral nectaries of both Echinacea species was studied, as well as the ultrastructure of the nectary of E. purpurea. Modified stomata on the nectary rim are the most likely exits for nectar, but creases in the epidermis may also participate. The nectary of E. purpurea is vascularized by phloem alone, which occurred adjacent to the epidermis. Companion cells possessed wall ingrowths, and these cells may unload arriving sugar destined for either an apoplastic or symplastic pathway. Lobed nuclei were a key feature of secretory parenchyma cells, as was a predominance of mitochondria, suggesting that energy-requiring eccrine secretion predominates in E. purpurea. E. angustifolia exhibited a generalist pollination system, with pollinating insects belonging to the orders Coleoptera, Diptera, Hymenoptera, and Lepidoptera. The pollination efficiency of visitors was determined by single insect visits to bagged, virgin inflorescences followed by quantifying pollen tubes at the bases of receptive styles and/or calculating the percentage of shrivelled styles. It was determined that bumble bees (Bombus spp.) were efficient pollinators, indicating that they would likely contribute much to the pollination of E. angustifolia. Grasshopper bee flies (Systoechus vulgaris Loew) were plentiful but individually were not efficient pollinators, but taken together, they provided much pollination. Golden blister beetles (Epicauta ferruginea Say) were efficient pollinators but where yellow-petalled flowers occurred, their numbers on E. angustifolia decreased. Honey bees (Apis mellifera L.) were efficient pollinators and were present in low numbers without managed introduction. Pierid (2003) butterflies were regular visitors and efficient pollinators, and likely contributed significantly to E. angustifolia pollination. When introduced, the alfalfa leafcutter bee (Megachile rotundata Fabr.) preferred not to forage on E. angustifolia and as such, these solitary bees were not suitable as managed pollinators. In large agricultural plantings of E. angustifolia, however, native insects may not be capable of providing sufficient pollination for seed production when floral competition occurs.
328

Varroa destructor chez l’abeille domestique (Apis mellifera) : impacts sur l’hémolymphe et les infections secondaires

Cournoyer, Antoine 11 1900 (has links)
L’abeille domestique (Apis mellifera) est un insecte qui contribue à l’agriculture par sa pollinisation. Le taux élevé des mortalités hivernales des colonies est préoccupant depuis des décennies au Canada. Plusieurs facteurs sont impliqués, particulièrement Varroa destructor; un parasite qui se nourrit du corps gras de l’abeille. Le développement d’outils adaptés permettrait un meilleur suivi des colonies. Le projet consiste à corréler l’infestation de varroa avec les concentrations en sucres sériques et les co-infections (virales et bactériennes). Cette étude compare dans le temps six ruches fortement infestées et six ruches traitées (témoins). Un prélèvement d’hémolymphe a été effectué pour mesurer les concentrations en sucres en utilisant un glucomètre humain préalablement validé. Les concentrations en sucres (glucose et tréhalose) dans l’hémolymphe étaient significativement plus faibles (p<0.001) dans les ruches fortement infestées que les témoins en septembre. L’analyse RT-PCR multiplexe de six virus (DWV A/B, BCQV, KBV, IAPV et ABPV) a démontré que les ruches fortement infestées présentent une infection simultanée virale avec des charges plus élevées que chez les ruches témoins (p<0.05) pour la majorité des virus, sauf pour ABPV. Chez les ruches fortement parasitées, les charges virales pour DWVA et BQCV sont plus élevées en septembre qu’en juillet (p≤0.0001). Serratia marcescens a été seulement détectée dans une ruche infestée et une ruche témoin. Une exposition continue et élevée à varroa occasionne, en automne, une augmentation des charges virales et une diminution des sucres, suggérant une altération de l’immunité, du métabolisme et des réserves. Ces paramètres provoquent une faiblesse et une mortalité des colonies. / The European honeybee (Apis mellifera) contributes to the agriculture by its pollination; however, the mean overwintering loss rate of colonies over the last decades in Canada is worrisome. Varroa destructor, which feeds on the fat bodies of honeybees, is considered one of the most important causes of bee colony declines. The development of adapted diagnostic tools would improve the monitoring of honeybee health. This project aims to correlate the infestation by varroa to the hemolymph sugar concentrations (trehalose and glucose) and bacterial and viral coinfections. Six highly infested and six treated hives were compared over time. Pooled hemolymph of honeybees was collected for sugar concentration measurements using a previously validated portable glucometer. The hemolymph samples were also submitted for bacteriology. Multiplex RT-PCR analyses were performed on pooled honeybees for six viruses: Deformed wing virus A and B (DWV-A/B), Bee Queen Cell Virus (BQCV), Acute Bee Paralysis Virus (ABPV), Kashmere Bee Virus (KBV), Israeli Acute Paralysis Virus (IAPV). The results show that, in September, sugar concentrations in hemolymph were significantly lower in highly infested hives (p<0.001). Infested hives showed markedly higher viral loads (p<0.05), except for ABPV. Viral loads were significantly higher (p≤0.0001) in September than in July for DWV-A and BQCV. Serratia marcescens was only detected in one infested hive and one control. Overall, a continued and severe exposure to varroa leads to increased viral charges and decreased sugar concentrations, suggesting alterations in immunity, metabolism and reserve mobilization. All these parameters contribute to the weakening and mortality of the colonies.
329

Factors and considerations in black economic empowerment deals in the small and medium size enterprises market

Smal, Charles 12 1900 (has links)
Thesis (MBA (Business Management))--Stellenbosch University, 2008. / ENGLISH ABSTRACT: Business persons engaging in BEE deals, pertaining to ownership, encounter many obstacles and challenges relating to the formulation of appropriate structures and solutions during the deal process. The SMME market is arguably one of the most critical contributors towards the SA GDP and a sector of the economy with the most growth potential as noted from recent history, especially relating to BEE ownership. It is in the above frame of reference that the research report attempts to follow a logical flow of events that the business persons in the SMME market would encounter. The report therefore has a holistic approach to this market and although many of the concepts could be applied to a variety of industries and even to other market segments, based on size, the primary objective and research has been centred around SMME’s. The core concepts that are covered relate to: - Understanding the essence of BEE and BBBEE as well as Government’s role as conduit to empowerment. The various elements under the BEE scorecard will also be a prominent factor as ownership only accounts for a portion of the entire BBBEE rating. - Aligning the BEE deal to strategy is a crucial consideration and entails attracting the right partner and ensuring that the BEE transaction is directed at value creation, growth and sustainability of the business. The transaction should make strategic and economic sense. - Determining firm value is in all probability one of the most complex issues and business owners should merely attempt to understand and interpret the vastly complicated process that may be presented by business brokers or valuers that facilitate the BEE deal. The fair value concept and required adjustments could be influential in the valuation process as well as choosing the correct valuation methodology. - Business tax structure. This is also a complex process that may vary significantly from business to business. Certain legislative impediments are influential and various amendments may also influence future structuring of BEE deals. The use of SPV’s is a prominent theme highlighted in this research report as it is very often the most preferred structure. - The BEE deal. This may have to consider hybrid financial solution from various sources, such as senior debt, franchise funding, mezzanine debt including venture capitalists, non-traditional lending sources and alternative supporting or indirect funders to the business. The lending criteria principles relating to cash conversion cycle, free cash flow and sustainable growth rate have also briefly been covered. BEE transactions inevitably enter an area of uncertainty for business persons when it comes to drafting business plans, determining the BEE scorecard, structuring the new shareholding and many other factors. In other words, they may not have the necessary business or financial acumen to prepare a satisfactory business proposal to attract lenders to the deal. It is therefore crucial to understand the different elements of the BEE deal formulation process, which is exactly the intent of this research report. / AFRIKAANSE OPSOMMING: Besigheidspersone wat SEB-transaksies met betrekking tot eienaarskap aangaan, ondervind baie struikelblokke en uitdagings in verband met die formulering van toepaslike strukture en oplossings wanneer die transaksie aangegaan word. Die KMMO-mark is stellig een van die mees kritieke bydraers tot die SA BBP en ’n sektor van die ekonomie met die meeste groeipotensiaal, soos die onlangse geskiedenis ons geleer het, veral met betrekking tot SEB-eienaarskap. Dit is met bogenoemde in gedagte dat hierdie navorsingsverslag poog om ’n logiese vloei van gebeure te volg wat die sakepersone in die KMMO-mark sal teëkom. Die verslag het dus ’n holistiese benadering tot hierdie mark en hoewel baie van die konsepte op ’n verskeidenheid nywerhede en selfs op ander marksegmente, gegrond op grootte, toegepas kan word, is die primêre doelwit en navorsing op KMMO’s gerig. Die kernkonsepte wat behandel word, het betrekking op: - Begrip van die kern van SEB en BBSEB asook die Regering se rol as geleibuis tot bemagtiging. Die verskillende elemente van die SEB-telkaart is ook ’n belangrike faktor aangesien eienaarskap net ’n gedeelte van die algehele BBSEB-aanslag verteenwoordig. - Die inlynstelling van die SEB-transaksie met die strategie is ’n kritieke oorweging en behels die lok van die regte vennoot en die versekering dat die SEB-transaksie tot waardeskepping, groei en volhoubaarheid van die besigheid gerig is. Die transaksie moet strategiese en ekonomiese sin maak. - Die bepaling van stewige waarde is in alle waarskynlikheid een van die mees komplekse kwessies en besigheidseienaars moet bloot probeer om die enorme gekompliseerde proses te verstaan en te interpreteer wat deur besigheidsmakelaars en waardeerders wat die SEB-transaksie fasiliteer, voorgelê word. Die billikewaarde-konsep en die vereiste regstellings kan invloedryk op die waardasieproses asook die keuse van die korrekte waardasiemetodologie wees. - Besigheidsbelastingstrukturering is ook ’n komplekse proses wat aansienlik van besigheid tot besigheid verskil. Sekere wetlike struikelblokke is invloedryk en verskeie wysigings kan ook toekomstige strukturering van SEB-transaksies beïnvloed. Die gebruik van SDV’s is ’n prominente tema wat in hierdie dokument uitgelig word aangesien dit in die reël die verkieslikste struktuur is. - Die SEB-transaksie sal moontlik hibridiese finansiële oplossings van verskeie bronne soos seniorskuld, franchise-befondsing, tussenskuld insluitend waagkapitaliste, nie-tradisionele uitleenbronne en alternatiewe ondersteunende of indirekte befondsers van die besigheid moet oorweeg. Die uitleenkriteriabeginsels met betrekking tot kontantomskeppingsiklus, vry kontantvloei en volhoubare groeikoers word ook kortliks gedek. SEB-transaksies betree onvermydelik ’n gebied van onsekerheid vir sakepersone wanneer dit kom by die opstel van besigheidsplanne, die bepaling van die SEB-telkaart, die strukturering van die nuwe aandeelhouding en baie ander faktore. Met ander woorde, hulle kan moontlik nie die nodige besigheids- of finansiële vernuf hê om ’n bevredigende besigheidsvoorlegging op te stel wat uitleners na die transaksie sal aantrek nie. Dit is dus kritiek om die verskillende elemente van die formulering van die SEB-transaksie te verstaan, wat presies die doel van hierdie navorsingsverslag is.
330

BIOCHEMICAL AND TOXICOLOGICAL IMPACT OF INSECTICIDE SYNERGISTS ON THE HONEY BEE APIS MELLIFERA L.

TODESCHINI, VALERIA 31 May 2017 (has links)
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.

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