Managed honey bee colonies face severe winter losses in northern climates. In my studies, interactions between genotypes of bees (genetically selected stock and unselected stock) with different levels of resistance and tolerance to varroa mites were assessed under a variety of treatment combinations to quantify effects of queen pheromone, acaricide treatment, wintering method, ventilation condition and pathogen infection on the costs and benefits associated with mite removal and mite-tolerance behaviors. In most of the experiments, mite-resistance caused greater varroa mite mortality within selected stock relative to unselected stock. Artificial and natural sources of queen pheromone caused greater varroa mite mortality within honey bee colonies relative to queenless colonies. While mite resistance had significant benefits, I showed that when producers selected colonies containing some mite resistance traits, it was traits associated with mite-tolerance and not mite-resistance were maintained and contributed to wintering success. Tolerance was effective at two levels of mites as obtained by late autumn treatment of colonies with oxalic but treatment did not improve wintering performance of either stock. Selected stock showed greater colony size, survival and resulted in more viable colonies in spring in comparison to unselected stock with similar initial mite levels (0.16 mites per bee). Selected stock showed greater relative wintering success than unselected stock when wintered indoors than when wintered outdoors but indoor wintering improved colony survival in both stocks relative to outdoor wintering. Carbon dioxide level increased within the winter bee cluster when colonies were maintained under restricted-ventilation (mean 3.82±0.031%, range 0.43-8.44%) and restricted ventilation increased mite mortality by 138% relative to standard-ventilation (mean 1.29±0.031%, range 0.09-5.26%), but restricted-ventilation did not affect bee mortality in comparison to standard-ventilation. In a laboratory study, I showed that Nosema inoculation (with co-infections of N. ceranae and N. apis) suppressed the effectiveness of mite removal behavior within selected bees relative to unselected bees. N. ceranae was more abundant than N. apis. Bees with greater mite removal capacities had higher costs associated with varroa-resistance as indicated by greater bee mortality rates when inoculated with varroa but bee mortality was not affected in Nosema inoculated bees.

My dissertation encompasses five different studies that are linked by a common theme the investigation of transposable element (TE) contributions to eukaryotic gene sequences. A detailed analysis of exonization events of LTR elements in the human genome shows the preference towards the fixation of LTR elements in gene untranslated regions, which supports the existing concept of a major role of LTR elements as a natural source of regulatory sequences. The ability of different classes of sequence similarity search methods to detect TE-derived sequences was evaluated. In general, the different search methods are found to be complementary, and combined search approaches are needed to systematically check any data set for all potential TE-associated coding sequences. On average, TE-derived exon sequences have low protein coding potential. In particular, non-coding TEs, are frequently exonized but unlikely to encode protein sequences. Many of these non-coding exonized TEs may be actually involved in gene regulation via the formation of double stranded RNA complexes with complementary TE-derived exons. The investigation of the relationship between human miRNAs and TEs shows that 55 experimentally verified human miRNA genes (~12%) originated from TEs. Overall, TE-derived miRNA genes are less conserved than non TE-derived miRNAs. The potential regulatory and functional significance of TE-derived miRNAs was explored. An ab initio prediction algorithm I developed was used to discover putative cases of novel TE-derived miRNA genes. A miRNA gene family, hsa-mir-548, was found to be derived from Made1 family of MITEs. The palindromic structure of the Made1 elements, and MITEs in general, points to a specific mechanism by which these sequences can be recognized and processed by the miRNA biogenesis pathway. MITEs may also represent an evolutionary link between siRNAs and miRNAs. An original model for a siRNA-to-miRNA evolutionary transition mediated by DNA-type TEs is proposed. This model is supported by the presence of evolutionary intermediate TE sequences that encode both siRNAs and miRNAs in the Arabidopsis and rice genomes. The siRNA-to-miRNA evolutionary transition is representative of a number of other regulatory mechanisms that evolved to silence TEs and were later co-opted to serve as regulators of host gene expression.

Tez (Yüksek Lisans) - Süleyman Demirel Üniversitesi, Fen Bilimleri Enstitüsü, Bitki Koruma Anabilim Dalı, 2008. / Bibliyografya var.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2006. / Title from title screen (site viewed May 23, 2007). PDF text: iv, 165 p. : ill. (some col.) ; 1.95Mb UMI publication number: AAT 3237062. Includes bibliographical references. Also available in microfilm and microfiche formats.

Ce manuscrit présente des études expérimentales sur l'évaporation de gouttes et la chimiotaxie de la mite.Une première partie s'intéresse à l'évaporation de spray dense au moyen d'une nouvelle approche, par analogie avec le mélange scalaire. Dans cette limite de forte densité en gouttes, où il y a saturation en vapeur au sein des structures constituantes, l'évaporation est principalement fonction de l'étirement auxquelles ces structures sont soumises. C'est en effet celui-ci qui conditionne le taux d'évacuation de cette vapeur interstitielle, ce qui permet de mettre les gouttes en contact avec un environnement plus sec, déclenchant ainsi leurs évaporations.Une deuxième partie s'intéresse à une application de la compréhension de cette dynamique d'évaporation de spray dense à un contexte d'entomologie: la chimiotaxie de la mite. Il s'agit du processus par lequel l'animal va se repérer dans un champ de concentration, pour localiser la source d'une substance attractive par exemple (ici de la phéromone sexuelle). Cette partie a tendu vers l'obtention d'une visualisation conjointe de la trajectoire de l'animal et du champ de concentration sous-jacent par la visualisation des gouttes. / This thesis present some experiments on droplets evaporation and moth chemotaxis.In a first part, dense spray evaporation is explained through a new approach, drawing an analogy with scalar mixing. In this high density droplets limit, where vapor saturation is reached within the structures, evaporation is mainly controlled by the intensity at which these structures are stretch. It is indeed the stretching that controls the rate at witch interstitial vapor is evacuated: droplets are thus in contact with a dryer environment, so they can start to evaporate.A second part take an interest in applying dense spray evaporation dynamic understanding to an entomologist situation: moth chemotaxis. This is the process by which animals find their way in a concentration field, such at finding a chemoattractant source for instance (sexual pheromone in our case). This part tended towards visualizing animal trajectory and concentration field underlying through droplets visualization simultaneously.

Master of Science / Department of Plant Pathology / Erick D. DeWolf / Wheat streak mosaic (WSM) is a devastating disease of winter wheat (Triticum aestivum L.) in Kansas. Although WSM can cause heavy crop losses, the severity of regional and statewide losses varies by year and location. Wheat streak mosaic is caused primarily by the Wheat streak mosaic virus (WSMV) and is spread by the wheat curl mite, Aceria tosichella Keifer. To infect fall planted wheat, both the virus and mite require a living, grass host to survive the summer months. The first research objective was to determine the risk of different grass species to serve as a source of WSM. Published experiments and surveys were reviewed to determine the suitability of each host based on a set of criteria. An analysis of the reports from the reviewed literature found 39 species to host both pests. Categorical analysis of these observations suggested that well-studied grass species could be placed in four risk groupings with ten species at high risk of carrying both pests. Furthermore, results from controlled experimentation generally agrees with results from field survey results for both pests. The second objective was to determine the weather and cropping factors that are associated with regional epidemics of WSM in Kansas. Historic disease observations, weather summaries, soil moisture indices, and cropping statistics were collected from Kansas crop reporting districts from 1995-2013. Binary response variables (non-epidemic case vs epidemic cases) were developed from different thresholds of district losses attributed to WSM. Variables associated with WSM epidemics were identified by a combination of non-parametric correlation, classification trees, and logistic regression. This analysis indicates that the total acres of wheat planted per season was associated with the low frequency of epidemics in Eastern Kansas. Temperature during September appears to influence the yield losses caused by WSM. Wheat planting generally begins during September and continues through October in the state. Temperature during the winter months (December-February) was also identified as important with warm conditions favoring outbreaks of disease. Dry soil conditions in February was also associated with epidemics of WSM. Models combining these variables correctly classified 60 to 74% of the cases considered in this analysis.

Made available in DSpace on 2014-06-11T19:22:56Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-03-28Bitstream added on 2014-06-13T20:10:09Z : No. of bitstreams: 1 delarco_m_me_sjrp.pdf: 172067 bytes, checksum: ff3cc84d9b26229bb4e0fa1f887bc9a0 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Esse trabalho teve como objetivo estudar o ciclo biológico de T. heveae em folíolos de seringueira dos clones RRIM 600, PB 235 e GT 1. Inicialmente foi estabelecida uma colônia de manutenção de T. heveae. As arenas de criação e para estudos da biologia foram confeccionadas a partir de folíolos de seringueira dos clones acima citados sendo mantidas sob condições controladas em câmara climatizada do tipo BOD com umidade relativa de 70+10%, fotoperíodo de 12 h, 28+0,1oC na fotofase e 25+0,1oC na escotofase. Três observações diárias foram realizadas, acompanhando-se o desenvolvimento de 60 ovos em folíolos de cada clone para verificação do estágio de desenvolvimento em que o ácaro se encontrava, assim como a oviposição das fêmeas. A fase mais longa registrada nos três clones foi a de ovo e o período mais curto foi o protoninfal. Em todos os clones estudados a fase de maior viabilidade foi a deutoninfal, e a menor, a larval. Quatorze fêmeas e quatro machos atingiram a fase adulta no clone PB 235, sendo observada uma taxa média de oviposição de 1,2 ovo/dia/fêmea. No clone RRIM 600, nove fêmeas e dois machos foram observados, sendo registrada a taxa de oviposição de 0,7 ovo/dia/fêmea. No clone GT 1, sete fêmeas chegaram à fase adulta com taxa média de 0,51 ovo/dia/fêmea. O ciclo completo da incubação do ovo até a morte do adulto durou 25 dias, em média, nos clones RRIM 600 e PB 235. A taxa intrínseca de crescimento populacional (rm) foi de 0,09; 0,08 e 0,02 nos clones PB 235, RRIM 600 e GT 1, respectivamente. O clone PB 235 possibilitou um melhor desenvolvimento de T. heveae, seguido pelo clone RRIM 600. O clone GT 1 foi o menos favorável ao desenvolvimento. / This work aims to study the biological cycle of T. heveae in rubber tree leaflets of clones RRIM 600, PB235 and GT 1. Initially, a maintenance colony was established. The breeding arenas and those for the study of the biology were created using leaflets of the aforementioned rubber tree clones, which had been kept under controlled conditions in a climatic chamber. Three daily observations were done, following the development of 60 eggs in each clone to check the developmental stage and female oviposition. The egg was the longest-lasting phase registered and the protonymph was the shortest period. The deutonymph was the most viable phase in all clones, whereas the least viable was the larval stage. Fourteen females and four males reached the adult stage in the clone PB 235, an average oviposition rate of 1.2 egg per day per female. In the RRIM 600 clone, nine females and two males were viable, and an oviposition rate of 0.70 egg per day per female was observed. In the GT 1 clone, seven females reached the adult stage, the average ovoposition rate was 0.51 egg per day per female. The complete cycle of incubation of the egg until the death of the adult lasted, on average, 25 days in RRIM 600 and PB 235 clones. The intrinsic rate of population increase (rm) was 0.09; 0.08 and 0.02 in clones PB 235, RRIM 600 and GT1, respectively. The clone PB 235 allowed a better development of T. heveae, followed by RRIM 600. The clone GT 1 was the least favourable for the development of that mite species.

Submitted by PATRICE JACOB SAVI (savipatricejacob@yahoo.fr) on 2018-04-13T23:56:05Z No. of bitstreams: 1 Savi_pj_me_jabo.pdf: 5321539 bytes, checksum: 55c0543813b08023f4e1f48c3330cf33 (MD5) / Approved for entry into archive by Alexandra Maria Donadon Lusser Segali null (alexmar@fcav.unesp.br) on 2018-04-16T10:40:16Z (GMT) No. of bitstreams: 1 savi_pj_me_jabo.pdf: 5321539 bytes, checksum: 55c0543813b08023f4e1f48c3330cf33 (MD5) / Made available in DSpace on 2018-04-16T10:40:16Z (GMT). No. of bitstreams: 1 savi_pj_me_jabo.pdf: 5321539 bytes, checksum: 55c0543813b08023f4e1f48c3330cf33 (MD5) Previous issue date: 2018-02-26 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / O ácaro-vermelho-do-tomateiro, Tetranychus evansi Baker e Pritchard (Acari: Tetranychidae), foi introduzido em diversos países da África e da Europa a partir da América do Sul. Nesses países, este ácaro encontrou condições favoráveis ao seu desenvolvimento e se tornou uma das principais pragas do tomateiro, podendo causar perdas de produtividade de até 90%. Devido ao seu elevado potencial biótico, o controle desse ácaro é dificultado pela baixa eficiência dos produtos empregados e pelas populações resistentes aos acaricidas. Dessa forma, o uso de plantas resistentes se torna essencial como uma alternativa ideal de controle, uma vez que permite a manutenção da praga em níveis inferiores aos de dano econômico, minimizando o impacto ambiental do uso de acaricidas e diminuindo os custos de produção. Diante disto, o objetivo deste trabalho foi selecionar genótipos de tomateiro provenientes da África que confiram resistência ao ácaro T. evansi utilizando os genótipos sul americanos de tomateiros selvagens como testemunha. Foram avaliados cinco genótipos de tomateiros comerciais Solanum lycopersicum L. oriundos do Institut National des Recherches Agricoles du Bénin (INRAB), sendo var. AKIKON, var. TOUNVI, var. KEKEFO oriundos do Benin, var. TOML4 oriundo do Senegal, var. TLCV15 oriundo da República Democrática de Congo, e os genótipos selvagens sul americanos: Solanum pennellii Correll LA-716 e Solanum habrochaites Knapp e Spooner var glabratum (PI134417 e PI134418) oriundos do Instituto Agronômico de Campinas, SP-Brasil. Foram realizados experimentos de preferência para atratividade e para o oviposição com chance e sem chance de escolha em laboratório, assim como a relação com a densidade de tricomas foliares com a preferencia do ácaro foram realizados. Foi realizado também um experimento de resistência por antibiose mediante a duração dos estádios de desenvolvimento, oviposição, viabilidade de ovos, sobrevivência nesses genótipos mantidos em câmara climatizada. Os genótipos de tomateiro africanos (AKIKON, TOUNVI, KEKEFO, TOML4 e TLCV15) possuem maior densidade de tricomas não glandulares especialmente o tipo Va, o que proporcionou maior preferência para atratividade e oviposição do ácaro T. evansi ao comparar com os resultados dos genótipos sul americanos de tomateiros (LA-716 e PI134417). Nenhum dos genótipos africanos testados apresentou resistência por antibiose. De acordo com nível de resistência dos genótipos testados porém, os selvagens da América do Sul (PI134417 e PI134418) foram altamente resistentes ao ácaro, os genótipos de tomateiro africanos TLCV15 e TOML4 foram moderadamente resistentes, enquanto AKIKON foi suscetível e os genótipos TOUNVI e KEKEFO foram altamente suscetíveis ao ácaro vermelho. / The tomato red spider mite Tetranychus evansi Baker and Pritchard (Acari: Tetranychidae) was introduced in several countries of Africa and Europe from South America. In these countries, this mite found favorable conditions for its development and becomes one of the main pests of tomato, which can cause yield losses of up to 90%. Due to its high biotic potential, the control of this mite is dificultated by the low efficiency of the chemicals used and populations resistant to acaricides. Thus, the use of resistant plants becomes essentials as an ideal control alternative, since it allows the pest to be kept at levels below the economic threshold, minimizing the environmental impact of the use of acaricides and reducing production costs. Therefore, the aim of this study was to select African tomato genotypes that confers resistance to red spider mite using the South American tomato genotypes as a control. Five commercial tomato genotypes of Solanum lycopersicum L. from Institut National des Recherches Agricoles du Bénin (INRAB) were evaluated: var. AKIKON, var. TOUNVI, var. KEKEFO from Benin, var. TOML4 from Senegal, var. TLCV15 from the Democratic Republic of Congo, and two wild tomato genotypes from South America: Solanum pennellii Correll LA-716 and Solanum habrochaites Knapp & Spooner f. glabratum (PI134417 and PI134418) from the Instituto Agronômico de Campinas, SP, Brasil. No-preference bioassay for attractiveness and oviposition was conducted in free choice and no choice tests as well as the relationship of the density of leaf trichomes with the preference of the red spider mite were realized. It was also carried out the antibiosis resistance bioassay evaluating immature development time, oviposition rate, egg viability and survival of T. evansi in these genotypes maintened under controlled laboratory conditions. African tomato genotypes (AKIKON, TOUNVI,KEKEFO, TOML4 e TLCV15) have a higher density of non - glandular trichomes especially type Va, which provided higher attractiveness preference and oviposition of the T. evansi mite when compared to the results of the South American (LA-716 and PI134417) tomato genotypes. None of the African tomato genotypes tested showed antibiosis resistance. According to the resistance level of the genotypes tested, South American tomato genotypes PI134417 and PI134418 were highly resistants to the red spider mite, African tomato genotypes TLCV15 and TOML4 were less suitables hosts for T. evansi, while AKIKON was suitable host and TOUNVI and KEKEFO were most suitable hosts for red spider mite. / CNPQ- PEC-PG: 190160/2015-2

Resumo: Avaliou-se, em casa de vegetação, o desenvolvimento populacional do ácaro Brevipalpus phoenicis e severidade da leprose em plantas de laranja da variedade Pêra, enxertadas sobre limão Cravo e as tangerinas Cleópatra e Sunki, com aproximadamente 9 meses de idade, submetidas a diferentes condições de deficiência hídrica. Os tratamentos foram estabelecidos em função da Capacidade de Campo (CC) e da fração de esgotamento de água (p) do solo, como segue: T1=25%CC (p=0,25); T2=40%CC (p=0,40); T3=55%CC (p=0,55); T4=70%CC (p=0,70). Decorridos 60 dias da indução ao estresse, realizou-se a colonização das mudas com 25 ácaros infectados e não infectados com o vírus da leprose, procedentes de uma criação sobre frutos com e sem lesões da doença. Os ácaros permaneceram colonizando às plantas por 55 dias, findos os quais, avaliou-se, em laboratório, sua população, contando-se o número de ovos, larvas, ninfas e adultos. Durante a colonização do B. phoenicis, avaliaram-se os sintomas da leprose, iniciando-se 21 dias após a colonização das plantas, e a intervalos de 7 dias. Empregou-se uma escala de notas visual para avaliar a severidade da leprose com base no número de lesões de leprose nos ramos, folhas e desfolha. Conclui-se que a disponibilidade de água para a planta influencia no desenvolvimento de B. phoenicis, visto que, em plantas submetidas a 25%CC, o número de ácaros foi maior que nos demais regimes hídricos, decrescendo à medida que a disponibilidade de água foi maior, atingindo seu menor índice populacional aos 70%CC. Em relação à severidade da leprose, as plantas submetidas a 25 e 40%CC obtiveram notas mais altas, evidenciando maior suscetibilidade... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: It was assessed, in greenhouse, the interaction of the leprosis mite Brevipalpus phoenicis with orange plants Pêra grafted on lemon Cravo variety and on tangerines Cleopatra and Sunki, with about 9 months old, submitted on different condition of water deficits and mite infestation. The treatments were determinate in a function of both, Field Capacity (CC) and soil water drain fraction (p), as this: T1=25%CC (p=0,25); T2=40%CC (p=0,40); T3=55%CC (p=0,55); T4=70%CC (p=0,70). After 60 days of stress induction, was made the colonization of plants with 25 mites that were reared on oranges with and without leprosis symptoms. The mites stayed in the plants for 55 days, after what, its population, counting the number of eggs, grub, nymphs and adults were assessed, in laboratory. During the B. phoenicis colonization, were assessed the leprosis symptoms, starting 21 days after the plants colonization, at intervals of 7 days. To this was used a notes ranking basing in the number of leprosies symptoms in the branches, leaves and desfoliate. Was concluded that the water availability had influence in B. phoenicis development, foundation that the plants submitted on 25%CC, had mite population higher than the others treatments, decreasing with the increase water availability, hitting the lowest population index on 70%CC. In relation with leprosis symptoms, plants submitted on 25 and 40%CC had the highest notes, evidencing more susceptibility of this plants to the disease and faster evolution of the symptoms. The rootstock Cravo and Cleopatra were more susceptible to the mite, showing the biggest population, 134,8 and 125,9 mites respectively, while Sunki showed the lowest population... (Complete abstract, click electronic access below) / Orientador: Carlos Amadeu Leite de Oliveira / Coorientador: Mara Cristina Pessoa da Cruz / Banca: Arlindo Leal Boiça Júnior / Banca: Marineide Rosa Vieira / Banca: Renato Beozzo Bassanezi / Banca: Mário Eidi Sato / Doutor

O morangueiro, Fragaria x ananassa Duchesne, tem sido extensivamente cultivado no sul de Minas Gerais. O ataque de pragas e a incidência de doenças tem causado prejuízos aos produtores dessa região. O ácaro rajado, Tetranychus urticae Koch (Acari: Tetranychidae), tem sido considerado a principal praga do morangueiro nessa região, onde é controlado principalmente com o uso de acaricidas sintéticos, que nem sempre apresentam resultados satisfatórios, aparentemente devido à seleção de populações resistentes. Ácaros da família Phytoseiidae são os predadores predominantes de outros ácaros em plantas cultivadas e da vegetação natural. São hoje conhecidas em todo mundo cerca de 2.700 espécies, quase 200 das quais tem sido encontradas no Brasil. Também são encontrados no cultivo do morangueiro no sul de Minas Gerais, porém nada se sabe sobre sua ocorrência em plantas da vegetação natural que circundam estes cultivos. Alguns estudos tem sido realizados nessa região para a implementação das práticas de controle biológico de ácaros em cultivos de morango. Os objetivos do presente estudo foram: a) comparar os níveis populacionais do ácaro rajado em cultivos representativos dos sistemas de produção orgânico e convencional do sul de Minas Gerais; b) determinar a semelhança da fauna de fitoseídeos de morangueiro cultivados organicamente e da vegetação natural circundante c) demonstrar a possibilidade de produzir morangos sem a utilização de agrotóxicos nesta região. Para a primeira parte do estudo, foram selecionados dois produtores de morangueiro em cada um de três municípios, um deles adotando o sistema convencional e o outro, o sistema orgânico. Não houve diferença estatística entre as médias dos níveis populacionais do ácaro rajado nos cultivos orgânicos e convencionais. Neoseiulus califonicus (McGregor), Neoseiulus anonymus (Chant) e Phytoseiulus macropilis (Banks) foram encontrados em morangueiro e também em plantas da vegetação natural. Os resultados sugeriram que N. anonymus possa ser mais apropriado que N. californicus para o controle do ácaro rajado na região de Cambuí. Na segunda parte do trabalho, avaliou-se o efeito de diferentes tratamentos sobre a população do ácaro rajado em um plantio estabelecido em Inconfidentes, estado de Minas Gerais. Os tratamentos consistiram da aplicação dos fungos Isaria fumosorosea Wize e Beauveria bassiana (Bals.) Vuill, de N. anonymus, do adjuvante KBRAdj, de abamectina e de um tratamento controle. Apesar dos baixos níveis de ocorrência do ácaro rajado em todos tratamentos, o número de acaro rajado no tratamento correspondente à liberação de N. anonymus foi significativamente menor que no tratamento correspondente à aplicação de abamectina. A realização deste trabalho permitiu as seguintes conclusões: a) a densidade populacional do ácaro rajado é aproximadamente a mesma em cultivos orgânicos e convencionais; b) a diversidade de ácaros predadores no cultivo orgânico é maior que no cultivo convencional; c) a vegetação nas proximidades cultivos do morangueiro é importante como abrigo aos ácaros predadores encontrados naquele cultivo; d) é possível a produção de morangos no sul de Minas Gerais sem o uso de acaricidas sintéticos. / Strawberry, Fragaria x ananassa Duchesne, has been extensively cultivated in southern Minas Gerais. Pest and disease outbreaks have caused losses to growers in this region. Two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), has been considered a major pest of strawberry in this region, where it is mainly controlled with the use of synthetic acaricides, producing results not always satisfactory, apparently due to the selection of resistant populations. Mites of the family Phytoseiidae are the predominant predators of other mites in crops and on plants of the natural vegetation. About 2,700 phytoseiid species are presently known, of which nearly 200 have been found in Brazil. These are also found on strawberry in southern Minas Gerais, but nothing is known about their occurrence in plants of the natural vegetation surrounding these crops. Some studies have been conducted in that region for the implementation of practical biological control of twospotted spider mite on strawberry. The objectives of this study were: a) to compare twospotted spider mite population levels on representative plantations of organic and conventional production systems; b) to determine the similarity of the phytoseiid fauna on strawberry crops grown organically and in the natural vegetation surrounding them; c) to demonstrate the ability to grow strawberry without the use of pesticides in this region. For the first part of the study, two strawberry growers were selected in each of three municipalities, one adopting the conventional growing system and the other the organic producing system. Difference between mean two-spotted spider mite population levels in those systems was not statistically significant. Neoseiulus califonicus (McGregor), Neoseiulus anonymus (Chant) and Phytoseiulus macropilis (Banks) were found on strawberry plants and also in the natural vegetation. The results suggested that N. anonymus may be more appropriate than N. californicus for spider mite control in Cambuí. In the second part of the study, the effect of different treatments on spider mite population in were evaluated in crop established in Inconfidentes, state of Minas Gerais. The treatments consisted of the application of the fungi Isaria fumosorosea Wize and Beauveria bassiana (Bals.) Vuill , of N. anonymus , of the adjuvant KBRAdj , of abamectina and a control treatment. Despite the low levels of occurrence of mite in all treatments, the number of two-spotted spider mite in the plots where N. anonymus was released was significantly lower than in the plots treated with Abamectina. This work led to the following conclusions: a) the population density of the mite is approximately the same in plantations of organic and conventional production systems; b) the diversity of predatory mites in fields of organic cultivation is higher than in fields of conventional cultivation; c) the vegetation in the vicinity of strawberry fields is important as reservoir of the predatory mites found in strawberry fields; d) Strawberry production in southern Minas Gerais can be done without the use of synthetic acaricides.