Dissertations / Theses on the topic 'Pyrgi'

Stephanitis pyri (Fabricius) (Heteroptera Tingidae), also known as “pear lace bug”, is a heavy fruit pest of Rosaceae common in Southern Europe. Its preferred host is Pyrus communis, a typical agricultural crop tree of high economical relevance in the region Emilia-Romagna (Northern Italy). The damages inflicted to leaves and fruits are marked yellowing and vanish-like tar spots, resulting into complete decline of untreated plants. The number of studies on Tingidae family is still limited, although several species are economically relevant in regions where pear tree orchards are widespread. A study to collect more information on behaviour and especially on feeding habits of the most relevant Tingidae species, S. pyri, was therefore initiated in 2006. The purpose of the study was to observe and record for the first time the feeding behaviour of S. pyri by Electrical Penetration Graph (EPG), to identify and analyze the different feeding phases and the interactions between the insect and the plant during the feeding process. The identification of EPG phases is based on waveforms, different in number and duration but typical of each species. To collect more information on feeding behaviour, the stylets of the insects were cut (stylectomy) during feeding phases and, after resin inclusion, the plant tissues containing the stylets were examined by optical and electron microscopy to match each stylet position to the typical waveform detected. These data allow to identify the plant tissues involved in feeding, establishing the degree of food specialization of the pest. Comparisons of duration and other parameters of feeding phases were then performed in different hosts, such as the pear varieties “William” and “Conference”, economically relevant cultivars, typical of Emilia Romagna. A study on feeding behaviour during host pre-contact and pre-penetration phases was also performed by choice tests, both in the field and in laboratory. Field experiments were also performed on S. pyri adult and nymph populations, to detect possible differences in development related the genotypes of the pear cultivars analyzed. The leaves of the two varieties are actually different from a morphological point of view: in Conference the leaves are more bended and often overlapping (thus offering a better hiding for insects), while in William they are flat and well separated. To exclude morphological factors in host choice, the experiments were repeated in laboratory on flat, round leaf disks. For field experiments, greenhouses with anti-aphid nets were prepared to restrain each individual S. pyri introduced and born, thus allowing a continuous time recording of insects and of their distribution on plants, and preventing the introduction of other species. The setting of laboratory conditions similar to the orchard ones allowed observations of typical features of behaviour and life cycle, such as orienteering, feeding choices, plant sensitivity or resistance to the pest, longevity, fitness, egg laying habits, etc. Besides choice tests, also no-choice tests were performed on the two pear cultivars to collect more information on development of S. pyri adult and nymph populations. The two cultivars were independently tested to avoid interferences in the host choice. The data collected could also be useful to increase information on the pear cultivar tested, to identify interesting traits for agronomical practices with low environmental impact. MATERIALS AND METHODS Insects Adult male and female individuals of Stephanitis pyri, progeny of individuals collected in orchards between the provinces of Ferrara and Rovigo (Northern Italy), were employed in all experiments. The parent individuals were collected by an entomological sheet on trees of wild pear, Pyrus pyraster (Burgsd.), common pear, Pyrus communis (L.) and apple, Malus pumila (Mill.). The insects were adult males and females of first, second and third generation, raised on P. communis cultivar “Abate” in full vegetative stage, in temperature-controlled rooms at 22 °C and 16:8 hours (day/night) photoperiod. Only for the choice test experiments on round-cut leaf portions, first generation S. pyri adults raised on Conference were employed, since this cultivar is considered more sensitive to the pest attack in comparison to William. Plants The plants employed in all experiments were one-year grafted plants of Pyrus communis belonging to the William, Abate and Conference cultivars, respectively grafted to Butyrra Hardi / BA29 (William and Abate) and on quince Sydo (Conference). All plants were free from chemical pest and fungus disease treatments, raised in plastic pots with standard, regularly watered soil for tree culture. Feeding habits and stylet position Technical equipments Many instruments were simultaneously employed: the Electrical Penetration Graph (EPG-DC, Wageningen University), a software for data reading (PROBE 3), an electric microknife (RF microcautery unit), a Faraday cage, a micromanipulator Narishige (Japan), a binocular Nikon 48161 microscope, an optical microscope Nikon Eclipse E200 (Tokyo, Japan), a Photoshop programs for image analysis, a transmission electron microscope (TEM) Hitachi H-800 (Electronic Microscopy Centre of the University of Ferrara), an ultramicrotome Reichart Om U2, (Germany). Semithin sections (about 1 μm thick) were observed at the optical microscope after staining with methylene blue; ultrathin sections (600 Å) for TEM were contrasted with uranyl acetate and lead citrate. EPG-DC parameters A comparison was performed between the cultivars Conference and William. For each 8-hr EPG-DC test, a different insect and a different plant were employed: all insects were placed on plants in standardized positions. A total of 20 trials with 20 different insects were performed for each cultivar. All results were validated, considering only those in which no interruptions were recorded in the trial period. The statistical analysis of all EPG parameters and the data obtained by comparison of the insect feeding behaviour in the two cultivars was performed by the Mann-Whitney test (p<0,05). Choice tests Choice test on leaves in laboratory. A total of 492 male and female S. pyri IIIrd generation adults were employed, raised on Abate. Each group of 6 individuals was placed inside a 15-cm Petri dish containing 6 leaves (3 from Conference and 3 from William), alternately arranged. The leaves were collected from different plants and immediately employed in the experiments. The insects were counted on each leaf every 5 minutes for 1 hour. Data were analyzed comparing the average insect number found on each cultivar by Student’s t test. These experiments were performed in September-October 2008. Choice test on leaf disks in laboratory. Each group of 6 individuals (male and female S. pyri IIIrd generation adults, raised on Abate) was placed inside a 15-cm Petri dish containing 3 leaf disks (2 cm diameter) per cultivar, alternately arranged. A total of 46 replicates were performed, for a total of 552 insects. The average number of insects found over the cultivar disks in each 5-minute interval was recorded and data were compared by Student’s t test, as previously described. Choice test on leaf disks in laboratory - insects raised on Conference. The experiments were performed as previously described, but employing male and female S. pyri IIIrd generation adults, raised on Conference cultivar (instead of Abate). A total of 46 replicates were performed, for a total of 552 insects. The average number of insects found over the cultivar disks in each 5-minute interval was recorded and data were compared by Student’s t test, as previously described. Choice test in field. A total of 15 plants for each cultivar (Conference and William) were employed, alternatively placing the grafted plants on two parallel rows, 40 cm apart. To isolate plants from attacks of other pests and from S. pyri parasites and predators, each row was covered by the anti-aphid net. The artificial infestation was performed with first generation S. pyri adults raised on Abate on 13 June 2007. Two adult insects were introduced for each plant and the infestation resulted uniform (relevant condition for experimental success). The observations started 3 days later and were performed at 3-day intervals by counting the number of adult insects on each plant and, later, also the number of nymphs derived from eggs laid by the adults initially introduced. At the end of tests the average number of insects found on each cultivar and sampling date was compared. The experiments ended on 25 July 2007 because of sharp plant decline due to heavy infestation by lace bugs. Statistical analyses were performed by Student’s t test as previously described. No-choice test in field camp. As in the previous experiments, a total of 15 one-year grafted plants of both cultivars Conference e William, arranged in parallel rows at a distance of 40 cm were employed. To isolate plants from attacks of other pests and from S. pyri parasites and predators, each row was covered by the anti-aphid net, that also prevented possible rain and wind damages. The artificial infestation was performed on 28 April 2008, employing first generation S. pyri adults raised on Abate: the infestation resulted uniform. RESULTS Feeding habits and stylet position This study performed on Stephanitis pyri allowed to record for the first time the feeding behaviour of the insect through EPG-DC recording. The data analysis allowed to characterize the EPG-DC waveform and identify the different phases. Two types of waveform were detected, waveform 1 and waveform 2, representing two different phases of insect feeding (respectively phase 2 and phase 3). Two other phases were identified: the initial one (phase 1), related to stylet penetration into leaf tissues, and the final one (phase 4), during which it is possible to observe at the stereomicroscope the stylet retrieval from the leaf tissues. Thus the EPG-DC of S. pyri is composed of four phases, two of which (phase 2 and phase 3), respectively identifiable by typical waveforms, waveform 1 and waveform 2. The total number of screenings performed and validated (including the data of comparison of phase duration between the two cultivars) was 85, each of them for a length of 8 hours. Correlation of stylet position with EPG-DC wave 1 and 2. The stylectomy in S. pyri to identify the stylet position in relation to the waveform type allowed to obtain in four experiments data on their position in relation to wave 2 (or feeding phase 3). In two cases the stylets penetrate until the borders of vascular bundles, and in the other two they penetrate the mesophyll, but do not go beyond the spongy parenchyma. These observations strongly support the hypothesis that during waveform 2 does S. pyri not perform a specialized tissue choice. Comparison of phases between Conference and William A total of 65 repeats (each lasting 8 hours) was performed using 31 adult f S. pyri or the Conference cultivar and 34 for the William one. The results of this series of experiments shows a significant difference (p = 0.014) in total duration of waveform 2, longer in William (average duration of 1906.65 seconds) in comparison to Conference (average duration 1275.73 seconds; standard error respectively 82.90 in William and 241.66 in Conference). Influence of Conference and William cultivars on S. pyri behaviour in pre-feeding phase and insect permanence on host plant Choice test on leaves in laboratory. S. pyri expresses a significant host preference for Conference leaves, already detectable after 10 minutes (an average of 1.32 individuals on Conference and of 0.8 individuals per leaf on William, p = 0.03). This difference increases with time. Choice test on leaf disks in laboratory. Again, a significant preference is expressed by S. pyri towards Conference from minute 35 to minute 40. The differences become non-significant from minute 41 to minute 55, then again are significant until the end of the experiment. Choice test on leaf disks – insects raised on Conference. The same series of experiments was repeated with insects raised on Conference cultivar. The results were very similar to those obtained in the previous experiments: Conference is the preferred host plant, with values similar to the previous ones. Choice test in field. The field experiments also support the preference of S. pyri towards Conference cultivar, with a significant difference (an average peak presence of about 65 individuals vs. about 35 in William). These results are also supported by the average number of nymphs on each plant, with a peak of almost 120 individuals per Conference plant, in comparison to about 40 individuals per William plant. No-Choice test in field. Towards the end of June a significant difference was noticed in the average number of individuals, in favour of William, but in July the significant difference favours Conference. The results also show that the peak of number of adults is reached after about five weeks on the William cultivar (average about 15 individuals per plant). The peak of the number of adult S. pyri on Conference appears later but reaches an average of almost 20 individuals per plant. Concerning the average number of nymphs per plant, it is always higher in William in comparison to Conference (respectively an average of 90 vs. 50). The average number rebalances in the last part of the experiment, reaching an average maximum peak of 120 individuals for both varieties. CONCLUSIONS - For the first time the EPG-DC waveform was recorded and characterized in all its phases in the pear leace bug, Stephanytis pyri (Fabricius) (Heteroptera, Tingidae). - Two economically relevant pear cultivars (“Conference” and “William”), common in orchards of Emilia-Romagna (Northern Italy) were analyzed for feeding habits and host choice in S. pyri. Significant difference were detected between the two cultivars in waveform 2 (feeding phase 3). - The stylet position was analyzed by optical and electron microscopy and was also determined in association to waveform 2 (feeding phase 3) - The choice tests on leaves, leaf disks and plants of both cultivars showed significant differences in host preference by. S. pyri. These difference are very likely related to morphological factors, the most relevant of which appears the leaf shape. - The field choice tests showed a host preference of to S. pyri towards Conference, when the cultivars are tested simultaneously. However, when plants are separately tested, the insects favour William for population development. The data collected in this study appear very interesting and require further investigations, especially concerning the complex relationships between S. pyri and the pear cultivar tested: these relationships may allow to identify interesting traits for agronomical practices with low environmental impact.

L'utilisation des insecticides dans la protection des vergers de poiriers, a ete conduite depuis des annees afin d'eradiquer le ravageur cle de ces cultures. Pourtant, le potentiel reproducteur du psylle reste un facteur important de son succes. Avec l'emploi abusif d'insecticides de plus en plus puissants, le ravageur s'est alors arme d'un moyen de lutte lui assurant une defense efficace contre les agressions xenobiotiques. Contrairement a la situation preoccupante de la resistance generalisee des psylles aux insecticides en amerique du nord, ce phenomene n'est pas encore en france un probleme d'actualite. La prise de mesures permettant de preserver l'efficacite des insecticides dans ce pays s'avere par consequent de toute urgence. La lutte chimique restant aujourd'hui le seul gage d'une production de qualite dans le verger commercial. Le present travail realise au laboratoire dans le cadre d'une lutte chimique raisonnee, montre, dans une premiere partie, que le rendement de l'amitraze, le dnoc et le monocrotophos dans la nature peut etre revalorise en tenant compte de la composition des populations de psylles presentes au moment des interventions phytosanitaires, et d'un facteur ecologique important, la temperature. Dans une deuxieme partie, le maintien d'une pression de selection d'un organophosphore, le monocrotophos, montre que le psylle possede un potentiel pour developper une resistance a cette famille d'insecticides. Une investigation basee a la fois sur l'etude de la resistance croisee au monocrotophos, le synergisme de sa toxicite par des inhibiteurs enzymatiques, et l'analyse d'activite de quatre enzymes, a permis de comprendre les mecanismes de resistance developpes dans la souche de psylles selectionnee a l'insecticide. La presence d'une acetylcholinesterase modifiee, moins sensible a l'inhibition du monocrotophos (70 fois) combinee avec une legere augmentation du metabolisme des monooxygenases a cytochrome p-450 (5 fois) etaient responsables du haut niveau de resistance developpe par les insectes resistants (150 fois)

La famille des phytoseiidae, acariens predateurs d'acariens phytophages, est caracterisee par un systeme de reproduction haplo-diploide a fecondation obligatoire, la pseudo-arrhenotoquie. La valeur adaptative de ce systeme est analysee chez un predateur de type generaliste, typhlodromus pyri scheuten, en relation avec les caracteristiques biologiques et ecologiques de cette espece. Le controle maternel de la sex-ratio est moins precis et la sex-ratio moins biaisee que chez les especes de type specialiste. Les differences de structure des populations sont essentiellement determinees par les comportements de ponte et d'accouplement et par l'ecologie nutritionnelle de ces especes. Ces comportements tendent a augmenter le taux d'heterogamie de t. Pyri. L'evolution de la pseudo-arrhenotoquie est egalement etudiee en recherchant les mecanismes impliques dans l'elimination des chromosomes paternels. Les effets physiologiques de l'age de la femelle a la premiere fecondation et d'un traitement des males a la tetracycline se traduisent par une augmentation de la proportion de males dans la descendance. Une etude complementaire sur l'heredite de marqueurs genetiques est entreprise par la technique des rapd (random amplified polymorphic dna). On met ainsi en evidence la transmission de materiel genetique paternel aux males hybrides issus de croisements entre deux souches de t. Pyri. Ces resultats suggerent l'intervention de facteurs cytoplasmiques et d'elements nucleaires dans les phenomenes d'empreinte genomique et d'heterochromatinisation conduisant a l'haploidie des males. Ce memoire conclut sur les perspectives de recherche emanant des travaux presentes

Le fenoxycarbe ro. 13-5223 ethyl (2-( p- phenoxy) ethyl ) carbamate, un regulateur de croissance des insectes (igr) a ete teste pour le controle des larves du dernier stade du psylle du poirier (psylla piry l. ), a la suite d'une application topique de differentes doses. La dl50 a ete determinee. Le fenoxycarbe s'est revele tres efficace, un fort % (60-80%) des individus meurt dans les jours qui suivent le traitement avec une dose de 5 ou 50 ug/larve. Le traitement provoque une perturbation de l'ecdysis et induit la formation d'individus intermediaires entre une larve et un adulte.

L'utilisation des insecticides dans la protection des vergers de poiriers a ete conduite depuis des annees afin d'eradiquer le ravageur cle de ces cultures. En raison de l'emploi abusif d'insecticides de plus en plus puissants et peu selectifs, des cas de resistance du psylle ont ete mentionnes dans de nombreux vergers commerciaux. Pour cette raison, les effets d'un produit non encore homologue en france contre le ravageur: le diflubenzuron, ont ete etudies. Le present travail realise au laboratoire pour l'etude des effets directs et indirects du diflubenzuron contre les ufs, les larves et les adultes montre, dans une premiere partie, que le produit n'est pas dote de proprietes ovicides. Quant a son action sur le developpement des larves issues des ufs traites, il apparait posseder une efficacite interessante. De plus, son application sur les differents stades larvaires donne de bons resultats notamment vis-a-vis des larves jeunes ; son efficacite a l'encontre des larves agees est plutot faible. Les doses letales obtenues pour les adultes sont sensiblement superieures a celles enregistrees chez les larves. Dans une deuxieme partie, l'etude des effets indirects du produit vis-a-vis des larves a confirme les resultats obtenus par contact direct. D'autre part, l'insecticide a manifeste des effets significatifs sur la fecondite des femelles. L'ensemble de ces resultats indique que lors d'une intervention phytosanitaire contre le psylle du poirier, le diflubenzuron peut etre preconise quand la population est constituee essentiellement de larves jeunes, son utilisation contre les larves agees et les adultes ne serait pas adequate. En raison de sa faible toxicite pour les mammiferes, de sa selectivite et de son innocuite pour les insectes utiles, le diflubenzuron pourrait jouer un role important dans la protection integree des vergers de poiriers

Le feu bactérien et le psylle causent d’importantes pertes économiques dans les zones de production du poirier dans le monde entier. Le développement de nouvelles variétés de poirier résistantes à ces bio-agresseurs constitue un enjeu majeur dans le cadre d’un programme de lutte intégrée. L’objectif de ce projet de thèse est l'étude du déterminisme génétique de la résistance vis-à-vis de ces deux bio-agresseurs. La thèse a été réalisée dans le cadre d’une collaboration internationale entre Fondazione Edmund Mach (Italie), Institut de Recherches en Horticulture et Semences (France) et Plant &amp; Food Research (Nouvelle-Zélande). Une descendance interspécifique de poirier T003 x ‘Moonglow’ a été développée avec pour objectif de cumuler les résistances au feu bactérien et au psylle provenant de variétés asiatiques et européennes de Pyrus. Deux cartes génétiques ont été élaborées pour T003 et ‘Moonglow’ sur la base de marqueurs SNP (Single Nucleotide Polymorphism) et SSR (microsatellite), et la cartographie de QTLs (Quantitative Trait Loci) a permis de démontrer le déterminisme polygénique de la résistance à ces bio-agresseurs. Une sélection assistée par marqueurs (MAS) peut donc être engagée pour ces deux caractères. Des incompatibilités génétiques ont aussi été observées dans une partie de la descendance, ce qui a permis de cartographier pour la première fois chez le poirier les zones du génome liées au phénomène de « nécrose hybride ». Le développement de marqueurs liés aux gènes létaux devrait permettre aux sélectionneurs d’éviter les combinaisons incompatibles en croisement qui peuvent impacter certains caractères agronomiques co-ségrégant avec ces gènes létaux<br>The goal of this PhD project was to study the genetic architecture of pear resistance to two of its most significant diseases and pests, fire blight and psylla, which cause severe yield losses in all the main pear production regions worldwide. The development of new pear varieties with resistance against these two biotic stresses is of major interest for Integrated Pest Management. This project was designed in a joint collaboration among Fondazione Edmund Mach (Italy), Institut de Recherches en Horticulture et Semences (France) and Plant &amp; Food Research (New-Zealand). The interspecific pear F1 progeny T003 x ‘Moonglow’ was developed with the purpose of cumulating resistances to fire blight and psylla deriving from Asian and European pear cultivars. Single nucleotide polymorphism (SNP) and simple sequence repeat (SSR)-based genetic maps were built for T003 and ‘Moonglow’. Quantitative Trait Loci (QTLs) were detected for the resistances, demonstrating their polygenic nature. Marker-assisted selection (MAS) can now be applied for these two traits. Furthermore, the segregating population exhibited genetic incompatibilities, and the genomic regions associated with hybrid necrosis were mapped for the first time in pear. Development of molecular markers linked to the lethal genes should allow breeders to avoid crosses leading to incompatible combinations that could affect the expression of important agronomic traits co-segregating with these genes

Face aux problemes de regulation des populations de psylles du poirier (psylla pyri), nous avons teste l'efficacite d'un nouvel insecticide, l'avermectine b1, d'une part sur le terrain (un verger a toulouse, un autre a valence et un troisieme a barcelone), et d'autre part au laboratoire de maniere plus approfondie. Cet insecticide a ete teste a differentes doses avec et sans adjonction d'huile blanche (2000 ppm), mais nous n'avons pas detecte d'eventuelle augmentation de toxicite due a cette derniere. A titre de reference, l'amitraze, qui est actuellement l'insecticide le plus frequemment utilise contre le psylle du poirier, a ete teste a la dose actuellement preconisee (600 ppm), et s'est revelee nettement moins active que l'avermectine b1. Les actions ovicide, larvicide et adulticide de l'avermectine b1 ont ete testees au laboratoire dans des conditions bien definies. Le calcul des doses letales 50 (dl 50) pour les divers stades de l'insecte a permis de comparer l'efficacite de l'avermectine b1 a celle d'autres insecticides precedemment etudies au sein du laboratoire. De plus, ce travail a permis la mise au point de protocoles de tests insecticides au laboratoire, notamment sur les ufs et les jeunes stades larvaires de p. Pyri

Le psylle du poirier cacopsylla pyri (l. ) est l'un des principaux ravageurs du poirier en france. Les etudes fondamentales et appliquees son nombreuses. Toutefois les observations de plein champ se limitent essentiellement a la surveillance. Nous presentons une etude de la dynamique des populations en relation avec la phenologie et la structure de la plante-hote dans le cadre de la bioecologie de l'espece. Nous exposons et discutons une synthese bibliographique mondiale sur les psylles du poirier et c. Pyri. Apres un expose critique des methodes d'etude et de notre strategie d'approche, nous presentons les donnees relatives a la phenologie et a la structure du poirier necessaires a une etude detaillee de sites d'installation. Nous developpons les aspects numeriques, structuraux (criteres de renouvellement des populations) et spatiaux de la dynamique des populations aux differentes echelles de l'espace ecologique (feuille, rameau, arbre, verger) et abordons les inter-relations du verger avec son environnement (migration, allochtonie). Ces donnees fournissent un panorama nouveau de la bioecologie de l'espece. Les particularites de la maturation ovarienne en plein champ sont precisees. L'importance du brassage des populations notamment est a prendre en compte dans la strategie de lutte et la gestion de la culture

Les effets de l'amitraze ont été d'abord testés contre les populations estivales de P. Pyri en vergers de poiriers dans trois régions différentes : l'efficacité est plus élevée dans les vergers d'Espagne que dans ceux de Toulouse et de la vallée du Rhône. Le produit exerce une action à court terme sur les adultes et à court et à long terme sur les larves. Il est peu efficace sur les oeufs. De plus la sensibilité des larves augmente avec la température.

Les haies plantées en bordure des cultures hébergent une entomofaune d'une grande diversité et leur fonction de réservoirs d'entomofaune auxiliaire n'est plus à démontrer. Dans le contexte actuel de développement d'une agriculture systémique basée sur la durabilité des systèmes de production, leur utilisation en protection intégrée entre dans le cadre des méthodes de protection dites de conservation de la biodiversité. L'objectif de ce travail est d'évaluer la fonctionnalité des haies dans la maîtrise des ravageurs des vergers, la culture choisie est celle du poiri (Pyrus communis L. ) et le ravageur visé est le psylle Cacopsylla pyri L. (Hemiptera, Psyllidae), ravageur clé des vergers de poiriers. Les résultats obtenus durant trois années sur un verger expérimental montrent que la haie influence la distribution des prédateurs dans la parcelle aux périodes de pullulation du ravageur, que cet effet n'est pas simplement un effet de lisière et que des déplacements d'auxiliaires ont lieu entre la haie et le verger en relation avec les effectifs de la proie. Cependant dans un contexte appliqué, les résultats obtenus sur cinq parcelles conduites en agriculture conventionnelle et biologique montre que l'impact des pratiques culturales, caractérisées par les traitements phytosanitaires est prépondérant surtout dans la composition du peuplement d'arthropodes des vergers et diminue grandement le rôle fonctionnel de la haie observé en verger expérimental<br>Hedgerows host a great of invertebrate species and play a great role as reservoirs of beneficial arthropods, which is not to be demonstrated any more. In the current context of a systemic agriculture based on the durability of the systems of production, their use in integrated protection management enters within the scope of the methods called "conservation biological control". The objective of this work is to estimate the hedge functionality in the control of the psylla Cacopsylla pyri (L. ) (Hemiptera, Psyllidae, key pest of the pear orchards, Pyrus communis (L. ). Our results, obtained in an experimental orchard during three consecutive years, show that the hedge influences the distribution of predators in the field during C. Pyri proliferation. This effect is not simply a border effect as movements of beneficials are observed between the hedge and the orchard in connection with prey density. In an applied context, the impact of chemical treatment is major on the composition of arthropods populating orchards and decreases the functional role of hedgerows observed in our experimental orchard

Le psylle commun du poirier psylla pyri (l. ) est le ravageur-cle de cette culture en france et dans de nombreux pays d'europe. Ce travail a recours au controle visuel des rameaux et au frappage des arbres pour suivre le niveau des populations du phytophage et des predateurs. Deux methodes d'isolement de larves de l'hote au laboratoire sont utilisees afin d'evaluer le taux de parasitisme. La dynamique des populations de p. Pyri est influencee par les facteurs climatiques, l'etat vegetatif de l'arbre et la faune auxiliaire mais aussi par les modes de gestion de la culture. La parasitofaune est constituee de micro-hymenopteres parasites et hyperparasites de larves de quatrieme et cinquieme stades de psylle. Trechnites psyllae ruschka et dans une moindre mesure prionomitus mitratus dalman sont les parasites primaires qui assurent la regulation des la premiere generation du ravageur. L'hyperparasitisme, essentiellement du a syrphophagus mamitus, apparait plus tard sur les hotes-relais entre la premiere et la deuxieme generation de p. Pyri (psylla pyrisuga foerster en verger et psylla melanoneura foerster dans l'aubepine). Le verger apparait etre un ecosysteme ouvert en inter-relation avec l'environnement

The goal of this PhD project was to study the genetic architecture of pear resistance to two of its most significant diseases and pests, fire blight and psylla, which cause severe yield losses in all the main pear production regions worldwide. The development of new pear varieties with resistance against these two biotic stresses is of major interest for Integrated Pest Management. This project was designed in a joint collaboration among Fondazione Edmund Mach (Italy), Institut de Recherches en Horticulture et Semences (France) and Plant & Food Research (NewZealand). The interspecific pear F1 progeny PEAR3 x ‘Moonglow’ was developed with the purpose of cumulating resistances to fire blight and psylla deriving from Asian and European pear cultivars. Single nucleotide polymorphism (SNP) and simple sequence repeat (SSR)-based genetic maps were built for PEAR3 and ‘Moonglow’. Quantitative Trait Loci (QTLs) were detected for the resistances, demonstrating their polygenic nature. Marker-assisted selection (MAS) can now be applied for these two traits. Furthermore, the segregating population exhibited genetic incompatibilities, and the genomic regions associated with hybrid necrosis were mapped for the first time in pear. Development of molecular markers linked to the lethal genes should allow breeders to avoid crosses leading to incompatible combinations that could affect the expression of important agronomic traits co-segregating with these genes

The aim of this study was to investigate the usefulness of image analysis for studying mite behaviour. Image analysis was used to convert video recordings of mites' locomotory behaviour into a series of x,y coordinates that, when joined, closely resemble the paths of mites. The coordinates were also used to calculate walking speed, direction of travel, turning frequency, turn bias and tortuosity. Two experimental arenas were developed and used to study the movement of three mite species: 1) a leaf disc arena for two-spotted spider mite, Tetranychus urticae Koch and European red mite, Panonychus ulmi (Koch); and 2), a cover-slip/tack-trap arena for Typhlodromus pyri Scheuten. Two-spotted spider mite exhibited a change in locomotory behaviour through a 48 minute period. Mites exhibited a significant decline in distance travelled, whereas the mean stationary time (per four minute interval) more than doubled, and the duration of stationary events increased steadily over the same period. A reduction in sampling frequency of mite coordinates from one per second to one every two seconds and every four seconds produced a 5% and 12% 'loss' in path length respectively. Sample period length was shown to greatly influence the results produced for some of the mean parameters calculated, however, a reduction in sample length from 3000 to 1500 coordinates was not considered to cause a major loss in information. The influence of the inherent mite movement could not be ignored and made it difficult to make decisions on the 'best' sample length to use. Some strong correlations were found between parameters used to analyse mite locomotory behaviour. In particular, arithmetic mean vector length, speed, total stationary time and total distance travelled were significantly correlated with each other. Mean angular deviation and weighted mean vector length, which both measure the degree of clustering around the mean heading angle, were strongly negatively correlated. Parameters which differentiated between 'straight' and 'tortuous' mite movement were found to be mean meander, absolute mean turn and fractal dimensions. Mean meander was thought to be the most 'powerful', while coefficient of a straight line, a commonly used parameter for measuring tortuosity, did not significantly differentiate between the two different behaviours. Frequency distributions of turns and standard deviations of the three mite species were very similar. All three species had a slight bias to turning right (clockwise) rather than to the left (counter-clockwise) and for each species certain angles occurred more often than would be expected in a 'perfect' normal distribution. A similar pattern also occurred with the frequency distribution of two-spotted spider mite heading angles, in that angles which were expected to occur more often, did not, and vice versa. The potential to use saturated salt solutions to control relative humidity on the arena was` demonstrated and indicated that relative humidity is likely to have an important influence on mite behaviour. Two-spotted spider mites appeared to move more quickly in an attempt to escape the unfavourable, extreme (10% and 95% R.H. at 25°C) moisture conditions. All three mite species displayed a characteristic edge-walking behaviour around the arenas. However, when 'edge' and 'non-edge' behaviours were compared, mean meander was the only parameter (of the parameters tested) which gave a significant difference. Behavioural responses of European red mite and T. pyri to sub-lethal (field rate) esfenvalerate were investigated and the results indicated that these mites did not seek the unsprayed halves of the arenas during the first 48 minutes. However, significant differences in most behavioural parameters to esfenvalerate residues were found with European red mite when whole arenas were compared. Image analysis is an extremely useful research tool for studying mite behaviour because of its ability to measure many parameters quickly. Careful choice of the environmental conditions, the sampling framework, and interpretation of data is essential for meaningful results.

Chapter 2 In solution, py(mi)ridinols 1.33, 1.34 and 1.35 are 2-, 5- and 28-fold more reactive antioxidants, respectively, than α-TOH (the most potent lipid-soluble antioxidant in nature). In order to develop a highly-reactive fluorescent indicator of lipid peroxidation in cells, we sought to couple these antioxidants with boron-dipyrro- methene (BODIPY) dyes, such that the resulting conjugates will display a significant fluorecence enhancement upon oxidation. This chapter details efforts towards the synthesis of these compounds. Chapter 3 Lipoxygenases are a family of important enzymes that catalyze the dioxygenation of arachidonic acid to yield a variety of potent lipid mediators that have been implicated in the pathogenesis of numerous degenerative conditions. We have undertaken a preliminary study of the effect of replacing the unsaturation in the related polyunsaturated lipid linoleic acid with cyclopropane rings on both the oxidizability of the lipid, as well as lipoxygenase’s ability to utilize it as a substrate. We anticipate that these analogs will be useful in co-crystallization studies with the enzyme that will provide unique insight into substrate acquisition, binding and the necessary conformation for catalysis.<br>Thesis (Master, Chemistry) -- Queen's University, 2011-11-10 16:15:05.643

Interspecific predation and cannibalism and associated rates of oviposition were assessed for adult female Metaseiulus occidentalis (Nesbitt) and Typhlodromus pyri Scheuten when provided non-limiting amounts of either eggs, larvae, protonymphs, or deutonymphs. Tests with all four stages of phytoseiids and larvae of Tetranychus urticae Koch were carried out at 25°C. At 15 and 12.5°C only larvae of phytoseiids and larvae of T. urticae were prey items. Predation by T. pyri was higher than M. occidentalis at 12.5 and 15°C, but more similar at 25°C. M. occidentalis did not feed appreciably on phytoseiid larvae at 15° and 12.5°C. Neither phytoseiid oviposited at 12.5°C when fed phytoseiid larvae, but T. pyri did at 15°C. We concluded that T. pyri was a more active predator at low temperatures and early-season predation on M. occidentalis immatures by T. pyri could contribute to displacement of M. occidentalis from apple orchards in western Oregon. The effects of prey species and prey density on the rates of inter- and intraspecific predation and oviposition of the two phytoseiid mite predators Metaseiulus occidentalis (Nesbitt) and Typhlodromus pyri Schueten were investigated through a series of laboratory experiments. Adult female predators were given mixed populations of phytoseiid larvae and larvae of a more preferred prey, the spider mite, Tetranychus urticae Koch, at different rates and proportions. T. pyri, more of a generalist predator, consistently showed higher rates of predation and cannibalism on phytoseiid immatures at most prey populations and proportions. Manly Preference Indices indicated that T. pyri switched to feed on phytoseiid immatures at higher population levels and proportions of T. urticae than did M. occidentalis. This ability to readily utilize phytoseiid immatures as prey indicated that maintaining both predators in a biological control program at low prey densities may require the use of active selective techniques that favour M. occidentalis. The differential impact of Zetzellia mali on the phytoseiids Metaseiulus occidentalis and Typhlodromus pyri was studied in laboratory experiments and by analysis of population data from experimental orchard plots containing either of the phytoseiid species, similar numbers of prey mites, and high or low populations of Z. mali. Five hypotheses were evaluated to explain why Z. mali had more impact on M. occidentalis in the field than on T. pyri.. Given equal opportunity, Z. mali adult females did not consume greater numbers of M. occidentalis eggs than T. pyri eggs nor did adult females of either phytoseiid species inflict greater mortality on Z. mali eggs or larvae through attack or consumption. There was no difference in the within tree association of Z. mali adult females with the eggs of either phytoseiid species nor were there differences in the way prey mites (all stages) were spatially partitioned between adult female Z. mali as compared with adults and deutonymphs of either of the two phytoseiids. The foraging area of adult female Z. mali and the oviposition locations of the two phytoseiids from both field and laboratory assessments were compared using spatial statistical procedures. M. occidentalis laid significantly more eggs in the primary foraging area of adult female Z. mali than did T. pyri. This spatial difference was the only factor tested which might explain the observed greater impact of Z. mali on M. occidentalis. Impact of these interspecific interactions and competition on the persistence of predatory mite guilds for the biological control of plant-feeding mites are discussed.<br>Graduation date: 1995

Genetics, gene flow, and distribution of pesticide resistance traits were examined for organophosphate (OP) resistance in three beneficial phytoseiid mites. Levels and genetics of OP resistance in Amblyseius andersoni were examined first. Laboratory strains from Italy and Oregon, USA, were compared in susceptibility to insecticides used in western Oregon fruit crops. The Italian strain was 80-100 times more resistant to the OPs azinphosmethyl, diazinon, malathion, and phosalone, as well as carbaryl, a carbamate. Significant differences were not found between strains for endosulfan or fenvalerate. Using backcross analysis, response of F1 hybrids to azinphosmethyl indicated OP resistance was semidominant. Through novel statistical analysis, backcross of F1 to parent strains revealed resistance was polygenic, with at least two loci. Reciprocal crosses demonstrated the presence of maternal effects, with increased variation associated with progeny of Oregon females. In the next set of experiments, electrophoresis of allozymes was used to estimate gene flow for Typhlodromus pyri. Ten populations from two apple growing valleys of Oregon were compared. Subpopulations were collected from in and around commercial apple orchards. Four loci unaffected by pesticide use were examined. FST was calculated at 0.115, and Nm as 2.08. No allelic patterns could be discerned for populations among or within valleys; however, more variation was present for mite populations within valleys than between them. Some inbreeding was found within populations. While from dispersal studies one would conclude T. pyri is nondispersive, allozymic analysis indicates there is moderate gene flow. Factors affecting OP resistance distribution in T. pyri and Metaseiulus occidentalis were examined. A diagnostic concentration of azinphosmethyl was used to determine OP resistance frequencies for populations of each species, collected in and near commercial apple orchards in two valleys. OP resistance in T. pyri populations was localized: mites from 10 m or more outside orchards were OP susceptible, while those within orchards were resistant. This indicated limited gene flow. All M. occidentalis populations were resistant, indicating a regional resistance pattern and high gene flow. Factors which were not significant in the distribution of OP resistance were: valley, degree of orchard isolation, host plant, and seasonality.<br>Graduation date: 1994