Whiteflies (Bemisia tabaci, Biotype B, Homoptera: Aleyrodidae) are pests of cotton crops, affecting the yield of the crop both indirectly and directly. These pests feed on the leaves of cotton plants and produce "honeydew," a sticky liquid excretion which covers the lint of the open cotton boll creating problems during the processing of the lint. High densities of these pests also can decrease the productivity of the cotton plant by stripping it of vital nutrients. The primary objective of this research was to screen 116 converted cotton race stocks for resistance to sweetpotato whiteflies. Responses of converted race stocks to whiteflies are compared to that of known susceptible commercial cultivars PSC 355 and Delta Pearl. Screens for antibiosis resistance to whitefly were established using excised leaves placed in a nutrient solution (¼ strength Hoagland's). Cohort populations of whiteflies were established on these leaves and followed daily to determine differences in developmental time as well as percent survival. Resistant candidates were determined using a chi-squared test comparing the ranked sums of leaf averages for the two selection criteria, whitefly developmental time and percent whitefly survival, of each cotton race stock to that of the putative known susceptibles (KS). These tests showed 6 converted race stocks to be significantly different (P ≤ 0.1) from the KS for at least one of the two selection criteria. Of these converted race stocks, M-9044-0154 and M-9044-0156 showed to have lower whitefly survival than the KS, while M-9644-0188, M-9644-0195, M-0044-0221, and M-9644-0242 showed whitefly to have an increased developmental time. Retesting of these six converted race stocks along with several others identified another race stock line, M-0044-0171, which was significantly different from the KS. Retesting also indicated that M-9644-0188 was different for survival in addition to developmental time which was determined in the original screening. Additional tests were conducted in the greenhouse and field to examine these race stock lines. Greenhouse screenings indicated that M-9044-0156 and M-9644-0188 contained possible non-preference resistance characteristics. Field screenings conducted in Weslaco and College Station, TX in 2002 and 2003 failed to provide useful data due to low densities of insects.

University, Diss., 2001--Bonn.

Orientador: Edson Luiz Lopes Baldin / Banca: João Roberto Spotti Lopes / Banca: André Luiz Lourenção / Resumo: A soja, [Glycine max (L.) Merrill], é um dos cultivos mais importantes para o Brasil, com alta produtividade e intensa participação no mercado externo. Seus grãos representam importante fonte nutricional para o homem e seus derivados são usados para alimentação animal ou mesmo na fabricação de energia renovável, na forma de biodiesel. No entanto, a produção desta leguminosa pode ser comprometida pelo ataque de insetos-praga, como a mosca-branca, Bemisia tabaci (Gennadius) biótipo B (Hemiptera: Aleyrodidae). Atualmente, este inseto é apontado como importante praga para a cultura da soja, devido às crescentes infestações e dificuldade no controle. Seu manejo é feito principalmente através de aplicações sucessivas de inseticidas sintéticos, as quais favorecem à rápida seleção de indivíduos resistentes. Desta forma, torna-se importante avaliar alternativas menos agressivas, alinhadas ao manejo integrado de pragas (MIP), com destaque para o uso de cultivares resistentes e indutores de resistência, como o silício. O monitoramento da alimentação de insetos sugadores por meio da técnica de EPG (Electrical Penetration Graph) tem auxiliado na caracterização de categorias e fatores de resistência de plantas frente ao ataque de insetos. Assim, neste trabalho, avaliou-se o comportamento alimentar de B. tabaci biótipo B em genótipos resistentes e suscetíveis de soja na presença e ausência de silício, utilizando-se EPG. Na primeira etapa, foram avaliados quatro genótipos de soja portadores ... / Abstract: Soybean, [Glycine max (L.) Merrill], is one of the most important crops for Brazil, with high productivity and strong participation in the foreign market. Soybeans represent important nutritional source for humans and their derivatives are used in animal nutrition or even renewable energy production, as biofuel. However, production of this crop may be affected negatively by the attack of insect pests, such as the whitefly, Bemisia tabaci (Gennadius) biotype B (Hemiptera: Aleyrodidae). This insect is currently indicated as an important pest for the soybean crop, due to the increasing infestations and difficulty in control. Its management is mostly done with successive spraying of synthetic insecticides that promote rapid selection of resistant individuals. Thus, it is important to evaluate less aggressive alternatives, aligned with the integrated pest management (IPM), with emphasis on the use of resistant cultivars and resistance inducers, as silicon. Monitoring sucking insects feeding using the EPG technique (Electrical Penetration Graph) has been helping in the characterization of categories and resistance factors of plants against insect attacks. In this study, the feeding behavior of B. tabaci biotype B was assessed in resistant and susceptible genotypes of soybean in the presence and absence of silicon using EPG. In the first stage, four genotypes of soybean bearers of different categories of resistance against the whitefly were assessed (KS-4202, tolerance; IAC-19, antixenosis; UX-2569-159, antibiosis e PI-227687, susceptible). At the same time, the types of trichomes present on the abaxial surface of the leaflets were characterized, in order to establish possible correlations with the feeding behavior of the whitefly. The results confirm the presence of antixenotic factors in the genotype IAC-19 (low duration of feeding in the phloem phase). ... / Mestre

The Bemisia tabaci (Gennadius) sibling species group is known to comprise several morphologically undistinguishable mitotypes which can be separated into seven major phylogeographic clades using the 3' half of the mitochondrial cytochrome oxidase I gene. B. tabaci is the only vector of begomoviruses; it transmits the complex of viruses that cause the cotton leaf curl disease, which has rapidly spread from Pakistan to the Philippines, at southeast of Asia, in the last decade. The study of B. tabaci mitotypes has been limited to variants of worldwide distribution and those associated to agroecosystems, however, the study of indigenous mitotypes has been scarce. This dissertation provides a comprehensive study of the phylogeography and population biology of mitotypes belonging to two major phylogeographic clades, the Asia II and the Americas. The Asia II major clade contains the highest number of mitotypes, in contrast, there is a large gap in knowledge about mitotypes associated to highly endemistic niches in the Americas. To study the population biology of mitotypes belonging to the Asia II major phylogeographic clade, two fragments of the mtCOI gene were amplified by polymerase chain reaction (PCR) for adult whiteflies sampled from mono and multi-cropping systems in the provinces of Punjab and Sindh in Pakistan. Phylogenetic analyses suggested that three indigenous mitotypes were distinctively distributed across ecosystems of Pakistan. The Asia II-5 and II-7 were found restricted to multi-cropping systems of Lahore, while the Asia II-1 was found widespread throughout the cotton growing region of Pakistan. Moreover, population analyses suggested the Asia II-1 is undergoing demographic expansion following a recent selective sweep or bottleneck. This event explains the predominance of Asia II-1 in Pakistan and its spread towards the southern province of Sindh. Additionally, differences in DNA polymorphism and diversity between mtCOI fragments derived in dissimilar evolutionary pairwise distances, suggestive of future implications in the “species” delimitation at a global scale when choosing one fragment over the other. The endosymbiotic bacteria assemblages associated to indigenous mitotypes Asia II-1, II-5 and II-7 were studied by analysis of 16S rRNA profiles. Besides the primary symbiont Portiera, Arsenophonus was detected almost fixed in the studied populations and several unique strains of Arsenophonus were detected in Asia II-5 and II-7, suggesting possible unique environmental adaptation capacities of these mitotypes. Hierarchical clustering of 16S rRNA profiles, proposed host-based and environmental-related differentiation. Additionally, the disruption of parallel cladogenesis between the primary symbiont and B. tabaci, disallows rejection of the hypothesis that gene flow among B. tabaci mitotypes occurs. To study the population biology of indigenous mitotypes belonging to the Americas major clade, adult whiteflies were sampled from ecosystems of nine provinces in Ecuador. Based on phylogenetic analyses, three indigenous and one invasive mitotype were detected. Among the indigenous, a previously unrecognized mitotype, named ECU3, was found. Moreover, mitotypes were found coexisting in five locations, and the invasive B is thought to have displaced endemic mitotypes to the northern and eastern coastal habitats of Ecuador.

Orientador: Marcelo Agenor Pavan / Coorientador: Mônika Fecury Moura / Coorientador: Marcelo Agenor Pavan / Coorientador: Renate Krause Sakate / Banca: Antonio Carlos Maringoni / Banca: Regiane Cristina Oliveira de Freitas Bueno / Banca: Valdir Atsushi Yuri / Banca: Julio Massaharu Marubayashi / Resumo: A família Solanaceae é uma das mais importantes na agricultura, pois engloba culturas economicamente expressivas no Brasil e no mundo. Dentre os fatores que podem prejudicar a produção de solanáceas, destacam-se as viroses e a infestação por insetos. Diante dos aspectos de grande importância descritos acima a tese foi dividida em dois capítulos. O capítulo 1, trata-se do primeiro relato de groundnut rigspot virus em jiló Brasil, na qual, anormalidades foram observadas em campos de produção de jiló (Solanum aethiopicum L.) no interior de São Paulo região de Itápolis. Sintomas de anéis necróticos e concêntricos foram observados em folhas e frutos, típicos da infecção por vírus. As plantas foram submetidas a extração de RNA total e RT-PCR. Os amplicons foram purificados e sequenciados, confirmando a identidade de 99% com GRSV vírus foi identificado como groundnut ringspot virus (GRSV). Testes biológicos foram realizados em Solanum melongena cv. Napolitana, S. melongena cv. Napoli, S. melongena cv. Roma, S. aethiopicum cv. Morro Grande, S. aethiopicum cv. Comprido Verde Claro, Datura stramonium, S. lycopersicum Mariana, Nicotiana tabacum "TNN", N. tabacum Virgínia, Capsicum annuum 'Magali R' e S. americanum. Ao final de 30 dias, todas as espécies testadas apresentaram sintomas sistêmica, evidenciando a infecção viral. No capítulo 2 foi abordado o desempenho de espécies crípticas de Bemisia tabaci em cultivares de pimentão. Com a introdução da espécie Mediterranean no Brasil, tamb... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The Solanaceae family is one of the most important in agriculture, since it encompasses economically expressive cultures in Brazil and in the world. Among the factors that may impair the production of solanaceous we can cite the viruses and the insect infestations. Faced with the aspects of great importance the thesis was divided into three chapters. Chapter 1, we describe the first report of groundnut rigspot virus in scarlet eggplant Brazil, in which abnormalities were observed in fields of scarlet eggplant (Solanum aethiopicum L.) in the interior of São Paulo region of Itápolis. Symptoms of necrotic and concentric rings were observed on leaves and fruits, typical of virus infection. The plants were submitted to extraction of total RNA and RT-PCR. The amplicons were purified and sequenced, confirming the 99% identity with groundnut ringspot virus (GRSV). Biological tests were performed in Solanum melongena cv. Napolitana, S. melongena cv. Napoli, S. melongena cv. Roma, S. aethiopicum cv. Morro Grande, S. aethiopicum cv. Comprido Verde Claro, Datura stramonium, S. lycopersicum Mariana, Nicotiana tabacum "TNN", N. tabacum Virgínia, Capsicum annuum 'Magali R' e S. americanum. At the end of 30 days, all species tested had systemic infection. In chapter 2, the performance of critical species of Bemisia tabaci in sweet pepper cultivars was addressed. With the introduction of the Mediterranean species in Brazil, also known as Q biotype, and having the information that it is very adapted to the pepper crop and has low susceptibility to different insecticides, pepper genotypes were tested for the performance and attractiveness of MEAM1 species. and MED. The accessions IAC 1549, IAC 1551 and IAC 1544 showed tolerance to Mediterranean species, because they exhibit low hatching of eggs, little adult emergence, and lower insect survival. In addition, IAC 1549 and IAC 1551 were unattractive to MED ... / Doutor

Made available in DSpace on 2016-08-12T19:18:24Z (GMT). No. of bitstreams: 1 ALAN MARTINS DE OLIVEIRA.pdf: 1485830 bytes, checksum: 11c6b8c6119b924bac2704d8a0abf2f0 (MD5) Previous issue date: 2008-02-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work aims to analyze technical and environmental aspects of the production of melon in the Homogeneous Zone in Mossoró emphasizing the fitosanitary control of the whitefly and Leaf Miner Fly. It is divided in two parts. In the Chapter I, an experiment was installed in Baraúna-RN, using delineation in blocks at random, in pieces subdivided in the time 6 x 5. There were six treatments in the piece: 1-physical control (blanket) chemist; 2-physical control (manta) + natural (oil of neem); 3-physical control (manta) + chemist + natural + peat (oil of neem); 4-physical control (manta) + chemist + peat + biological (trichoderma); 5-chemical control; 6-testifies. There were five times of evaluation in the sub piece of pest infestation: 20°, 28°, 36°, 44° and 52° DAT Days After the transplanting. Quantitative characteristics were analyzed: counting of nymphs and adults of whitefly and, larvae and adults of Leaf Miner Fly; qualitative characteristics in the fruits: mass, soluble solids, pulp firmness and pH. The use of alternative methods: biological, physical, natural control and peat have positive effects when used in the associate form. So, it is possible to reduce the use of pesticides in the melon. In the Chapter II, it was used like methodological proceedings the exploratory and descriptive search. There were valued data of questionnaires devoted to the owners or managers of the producing enterprises of melon, through probabilistic sample. It was checked that the short cycle of the culture, the model based on the monoculture, the agricultural mechanization, the elevated consumption of energy and the use of pesticides and chemical fertilizers associated to the marketing demands of qualitative and quantitative characteristics of the results, are affecting the sustainability of the culture of melon. In the final considerations, we realize that the technologies and the developed methods of production, aiming to pay attention to the growing demand of the result, especially of the rich countries, are untenable in the environmental optics; besides proposing larger searches aiming the sustainability: economical growth with ecological care and social equity / Este trabalho objetiva analisar aspectos técnicos e ambientais da produção de melão na Zona Homogênea Mossoroense, com ênfase ao controle fitossanitário das mosca-branca e mosca-minadora. Está dividido em duas partes. No Capítulo I, instalou-se um experimento em Baraúna-RN, usando delineamento em blocos ao acaso, em parcelas subdivididas no tempo 6 x 5. Na parcela constaram seis tratamentos: 1- controle físico (manta) + químico; 2- controle físico (manta) + natural (óleo de nim); 3- controle físico (manta) + químico + turfa + natural (óleo de nim); 4- controle físico (manta) + químico + turfa + biológico (trichoderma); 5- controle químico; 6- testemunha. Na subparcela constaram cinco tempos de avaliação de infestação de pragas: 20º, 28°, 36°, 44° e 52° DAT Dias Após o Transplantio. Analisaram-se características quantitativas: contagem de ninfas e adultos de mosca-branca e, larvas e adultos de mosca-minadora; características qualitativas nos frutos: massa, sólidos solúveis, firmeza de polpa e pH. O uso de métodos alternativos: controle biológico, físico, natural e turfa têm eficiência quando usados de forma associada. Assim, é possível reduzir o uso de agrotóxicos no melão. No Capítulo II, utilizou-se como procedimentos metodológicos a pesquisa exploratória e descritiva. Avaliou-se dados de questionários aplicados aos proprietários ou gestores das empresas produtoras de melão, por meio de amostragem probabilística. Verificou-se que o ciclo curto da cultura, o modelo baseado na monocultura, a mecanização agrícola, o elevado consumo de energia e o uso de agrotóxicos e fertilizantes químicos, associados às exigências mercadológicas de características quali-quantitativas dos frutos, estão afetando a sustentabilidade da atividade meloeira. Nas considerações finais, destaca-se que as tecnologias e os métodos de produção desenvolvidos, visando atender à crescente demanda do fruto, notadamente dos países ricos, são insustentáveis na ótica ambiental; além de propor pesquisas mais abrangentes quanto aos princípios norteadores da sustentabilidade: crescimento econômico com prudência ecológica e eqüidade social

Les invasions biologiques ont des conséquences écologiques telles que l'émergence de pathogènes et de ravageurs. Les populations invasives font face à de nouvelles conditions biotiques et abiotiques qu'elles doivent surmonter. Ces invasions biologiques sont des systèmes modèles pour étudier l'évolution sur de courtes échelles de temps car elles nécessitent une adaptation rapide qui fait intervenir différents processus (sélection naturelle, dérive, plasticité phénotypique). Du fait des introductions multiples et de l'hybridation, une augmentation de la variabilité génétique nucléaire peut-être observée dans ces populations, support d'une réponse adaptative plus rapide. De plus, chez les insectes, les symbiotes peuvent jouer un rôle important dans l'adaptation, contribution encore largement inconnue. Le ravageur de culture Bemisia tabaci est un complexe d'espèces dont les barrières reproductives sont peu connues et dont les différentes entités --- les cytotypes --- présentent des cortèges symbiotiques qui leur sont spécifiques. Grâce à une description de la dynamique spatio-temporelle de ces cytotypes, en contexte invasif en France et plus largement dans le bassin méditerranéen, nous avons constaté la présence simultanée de deux de ces entités et nous nous sommes interrogés sur un éventuel remplacement ou une coexistence. Cette situation originale nous a permis de tester leurs limites reproductives grâce à des microsatellites et des tests comportementaux, ainsi que la possibilité de transferts horizontaux de bactéries. Transferts que nous avons tenté de reproduire en laboratoire. Nous avons aussi développé des marqueurs RADSeq pour de futures analyses génomiques / Biological invasions have ecological consequences such as the emergence of pathogens and pests. Invasive populations face new biotic and abiotic conditions that they have to overcome.These biological invasions are model systems to study the evolution over short time scales because they require rapid adaptation that involves different processes (natural selection, drift, phenotypic plasticity).Because multiple introductions and hybridization, an increase in the nuclear genetic variability may be observed in these populations, supporting a faster adaptive response.Moreover, in insects, symbionts can play an important role in adaptation, a contribution largely unknown yet.Bemisia tabaci crop pest is a complex of species whose reproductive barriers are poorly known and whose different entities --- the cytotypes --- have symbiotic associations specific to them.Through a spatio-temporal dynamics description of these cytotypes in invasive context in France and more widely in the Mediterranean bassin, we found the simultaneous presence of both of these entities and we wondered about a possible replacement or coexistence.This peculiar situation has allowed us to test their reproductive boundaries with microsatellites and behavioral tests, as well as the possibility of horizontal transfer of bacteria. Transfers that we tried to reproduce in the laboratory. We have also developed RADSeq markers for future genomic analyzes

Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) biotype B is a cosmopolitan, devastating insect pest due to their direct damages and transmission of plant viruses. Entomopathogenic fungi comprise the most diverse group of pathogens regulating arthropod pest populations in agroecosystems. Anamorphic fungal entomopathogens, including Beauveria bassiana, Isaria fumosorosea, and Lecanicillium spp., are among the main biocontrol agents of whitefly populations. Advances in research focusing on virulence, mass production, formulation, and storage stability of fungal propagules are imperative for the development of efficient mycopesticides toward whiteflies and other soft-bodied insects. Therefore, this study placed emphasis on screening for virulent fungal strains, enhancement of efficacy using nonionic surfactants in spray tank-mix, development of liquid culture conditions for rapid production and stabilization processes of single-yeast like cells known as blastospores. Firstly, we selected virulent strains of B. bassiana and I. fumosorosea displaying fastest speed of kill and inciting highest mortality levels of whitefly nymphs and adults along with their ability to produce high numbers of conidia on moistened parboiled rice. Secondly, insecticidal performance was enhanced by combining nonionic surfactants with spore suspensions rendering additive or synergistic effects. These surfactants also allowed reducing the volume application rate without altering fungal bioefficacy. Results from liquid fermentation studies using B. bassiana and I. fumosorosea revealed that appropriate amounts of inexpensive ingredients, such as cottonseed flour and glucose, are suitable for the rapid production of high yields of blastospores (3 days pre-culture and 2-3 days culture). The resultant blastospores of various strains survived well to desiccation and remained viable for more than one year under refrigeration. Moreover, these air-dried blastospores of both fungal species showed higher virulence against whitefly nymphs when compared with solid-substrate produced conidia. Optimized liquid culture production for B. bassiana blastospores was also achieved through the manipulation of oxygen rates and osmotic pressure in the liquid media. Furthermore, these blastospores produced in highly aerated and hyperosmotic liquid medium containing 140 g glucose L-1 were also more virulent to whitefly nymphs than those cells derived from low-osmotic medium amended with 40 g glucose L-1. These optimal conditions were also scaled up in 5-L bioreactor that yielded 1-2 × 1012 viable blastospores L-1 in 6 days at a cost of US$ 0.19 L-1. These blastospores were formulated with diatomaceous earth for air drying or for spray drying. Formulated blastospores of B. bassiana survived dehydration using both drying methods and showed improved shelf life when stored under vacuumpackaged at 4 °C rather than 28 °C. However, when these blastospores were actively packaged with dual action oxygen-moisture scavenging system, blastospores showed prolonged stability for up to 7 months at 28 °C and still remained virulent to whiteflies. Therefore, this low-cost production and stabilization method for the rapid production of shelf stable, virulent blastospores of B. bassiana and I. fumosorosea may expand the commercial use of mycopesticides for insect control in mainstream agriculture. / A mosca-branca, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) biótipo B, é uma praga cosmopolita e devastadora devido aos prejuízos oriundos dos seus danos diretos e transmissão de vírus. Fungos entomopatogênicos compreendem um grupo diversificado, que desempenha ação importante na regulação de populações de praga em agroecossistemas. Fungos ascomicetos anamórficos, como Beauveria bassiana, Isaria fumosorosea e Lecanicillium spp., constituem relevantes agentes de biocontrole de moscas-brancas. Avanços na pesquisa focando virulência, produção massal, formulação e estabilização de propágulos fúngicos são fundamentais para o desenvolvimento de micopesticidas eficientes contra moscas-brancas e outros insetos. Desta forma, este trabalho objetivou selecionar isolados fúngicos virulentos à mosca-branca; aumentar a eficácia mediante uso de surfactants não-iônicos em suspensões conidiais; desenvolver meios de cultura para produção rápida e estável por fermentação líquida submersa de células leveduriformes conhecidas por blastosporos. Na primeira etapa, isolados virulentos de B. bassiana e I. fumosorosea foram selecionados pela rápida e elevada atividade inseticida a ninfas e adultos de mosca-branca, bem como alto rendimento de conídios em arroz parboilizado. A adição de surfactantes organosiliconados permitiu a redução do volume de calda aplicado com resultados aditivos ou sinérgicos de controle. Foi ainda verificado que altos rendimentos de blastosporos tanto de B. bassiana como I. fumosorosea foram obtidos em curto tempo de fermentação líquida (3 dias de précultivo e 2-3 dias de cultivo) usando nutrientes de baixo custo, como glucose e farelo de algodão. Esses blastosporos foram tolerantes à dessecação e mantiveram viabilidade por mais de um ano sob refrigeração (4 °C). Os blastosporos foram mais virulentos que conídios aéreos, o que coloca esta estrutura como a mais indicada como ingrediente ativo em bioinseticidas para moscas-brancas. Mediante manipulação nutricional e física do ambiente de fermentação, a produção de blastosporos de B. bassiana foi optimizada mediante aumento da aeração e pressão osmótica do meio líquido. Blastosporos produzidos em meio líquido altamente aerado e hiperosmótico (140 g glucose L-1) mostraram-se mais virulentos à mosca-branca em relação àqueles produzidos em meio hipo-osmótico (40 g glucose L-1). Esse processo foi reproduzido em escala piloto usando biorreator de 5 L resultando numa produção de 1-2 × 1012 blastosporos viáveis L-1 em apenas 3 dias a um custo de US$ 0,19 L-1. Blastosporos de B. bassiana formulados com terra de diatomáceas e secados em fluxo de ar contínuo, ou secados em spray dryer tiveram estabilidade extendida por até 8 meses a 4 °C e superior em relação a 28 °C. Durante empacotamento, o uso de sachês absorventes de oxigênio e umidade prolongou consideravelmente a viabilidade de blastosporos armazenados a 28 °C por até 7 meses sem afetar sua eficiência contra mosca-branca. Em suma, esses resultados demonstram a viabilidade técnica e econômica de produção de blastosporos virulentos de B. bassiana e I. fumosorosea, tolerantes à dessecação e estáveis durante armazenamento. Esta tecnologia é uma nova opção que pode contribuir para expansão comercial de bioinseticidas à base de fungos entomopatogênicos.

Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) biotype B is a cosmopolitan, devastating insect pest due to their direct damages and transmission of plant viruses. Entomopathogenic fungi comprise the most diverse group of pathogens regulating arthropod pest populations in agroecosystems. Anamorphic fungal entomopathogens, including Beauveria bassiana, Isaria fumosorosea, and Lecanicillium spp., are among the main biocontrol agents of whitefly populations. Advances in research focusing on virulence, mass production, formulation, and storage stability of fungal propagules are imperative for the development of efficient mycopesticides toward whiteflies and other soft-bodied insects. Therefore, this study placed emphasis on screening for virulent fungal strains, enhancement of efficacy using nonionic surfactants in spray tank-mix, development of liquid culture conditions for rapid production and stabilization processes of single-yeast like cells known as blastospores. Firstly, we selected virulent strains of B. bassiana and I. fumosorosea displaying fastest speed of kill and inciting highest mortality levels of whitefly nymphs and adults along with their ability to produce high numbers of conidia on moistened parboiled rice. Secondly, insecticidal performance was enhanced by combining nonionic surfactants with spore suspensions rendering additive or synergistic effects. These surfactants also allowed reducing the volume application rate without altering fungal bioefficacy. Results from liquid fermentation studies using B. bassiana and I. fumosorosea revealed that appropriate amounts of inexpensive ingredients, such as cottonseed flour and glucose, are suitable for the rapid production of high yields of blastospores (3 days pre-culture and 2-3 days culture). The resultant blastospores of various strains survived well to desiccation and remained viable for more than one year under refrigeration. Moreover, these air-dried blastospores of both fungal species showed higher virulence against whitefly nymphs when compared with solid-substrate produced conidia. Optimized liquid culture production for B. bassiana blastospores was also achieved through the manipulation of oxygen rates and osmotic pressure in the liquid media. Furthermore, these blastospores produced in highly aerated and hyperosmotic liquid medium containing 140 g glucose L-1 were also more virulent to whitefly nymphs than those cells derived from low-osmotic medium amended with 40 g glucose L-1. These optimal conditions were also scaled up in 5-L bioreactor that yielded 1-2 × 1012 viable blastospores L-1 in 6 days at a cost of US$ 0.19 L-1. These blastospores were formulated with diatomaceous earth for air drying or for spray drying. Formulated blastospores of B. bassiana survived dehydration using both drying methods and showed improved shelf life when stored under vacuumpackaged at 4 °C rather than 28 °C. However, when these blastospores were actively packaged with dual action oxygen-moisture scavenging system, blastospores showed prolonged stability for up to 7 months at 28 °C and still remained virulent to whiteflies. Therefore, this low-cost production and stabilization method for the rapid production of shelf stable, virulent blastospores of B. bassiana and I. fumosorosea may expand the commercial use of mycopesticides for insect control in mainstream agriculture. / A mosca-branca, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) biótipo B, é uma praga cosmopolita e devastadora devido aos prejuízos oriundos dos seus danos diretos e transmissão de vírus. Fungos entomopatogênicos compreendem um grupo diversificado, que desempenha ação importante na regulação de populações de praga em agroecossistemas. Fungos ascomicetos anamórficos, como Beauveria bassiana, Isaria fumosorosea e Lecanicillium spp., constituem relevantes agentes de biocontrole de moscas-brancas. Avanços na pesquisa focando virulência, produção massal, formulação e estabilização de propágulos fúngicos são fundamentais para o desenvolvimento de micopesticidas eficientes contra moscas-brancas e outros insetos. Desta forma, este trabalho objetivou selecionar isolados fúngicos virulentos à mosca-branca; aumentar a eficácia mediante uso de surfactants não-iônicos em suspensões conidiais; desenvolver meios de cultura para produção rápida e estável por fermentação líquida submersa de células leveduriformes conhecidas por blastosporos. Na primeira etapa, isolados virulentos de B. bassiana e I. fumosorosea foram selecionados pela rápida e elevada atividade inseticida a ninfas e adultos de mosca-branca, bem como alto rendimento de conídios em arroz parboilizado. A adição de surfactantes organosiliconados permitiu a redução do volume de calda aplicado com resultados aditivos ou sinérgicos de controle. Foi ainda verificado que altos rendimentos de blastosporos tanto de B. bassiana como I. fumosorosea foram obtidos em curto tempo de fermentação líquida (3 dias de précultivo e 2-3 dias de cultivo) usando nutrientes de baixo custo, como glucose e farelo de algodão. Esses blastosporos foram tolerantes à dessecação e mantiveram viabilidade por mais de um ano sob refrigeração (4 °C). Os blastosporos foram mais virulentos que conídios aéreos, o que coloca esta estrutura como a mais indicada como ingrediente ativo em bioinseticidas para moscas-brancas. Mediante manipulação nutricional e física do ambiente de fermentação, a produção de blastosporos de B. bassiana foi optimizada mediante aumento da aeração e pressão osmótica do meio líquido. Blastosporos produzidos em meio líquido altamente aerado e hiperosmótico (140 g glucose L-1) mostraram-se mais virulentos à mosca-branca em relação àqueles produzidos em meio hipo-osmótico (40 g glucose L-1). Esse processo foi reproduzido em escala piloto usando biorreator de 5 L resultando numa produção de 1-2 × 1012 blastosporos viáveis L-1 em apenas 3 dias a um custo de US$ 0,19 L-1. Blastosporos de B. bassiana formulados com terra de diatomáceas e secados em fluxo de ar contínuo, ou secados em spray dryer tiveram estabilidade extendida por até 8 meses a 4 °C e superior em relação a 28 °C. Durante empacotamento, o uso de sachês absorventes de oxigênio e umidade prolongou consideravelmente a viabilidade de blastosporos armazenados a 28 °C por até 7 meses sem afetar sua eficiência contra mosca-branca. Em suma, esses resultados demonstram a viabilidade técnica e econômica de produção de blastosporos virulentos de B. bassiana e I. fumosorosea, tolerantes à dessecação e estáveis durante armazenamento. Esta tecnologia é uma nova opção que pode contribuir para expansão comercial de bioinseticidas à base de fungos entomopatogênicos.

Natural enemies provide critical population regulation of many pest species, though their effects are not commonly incorporated into agricultural management decisions. Conservation biological control is an important tool that can be implemented to minimize pest damage, but applying it requires appropriate understanding of pest and natural enemy relationships. Through experimental cotton field trials, I identified predator: prey ratios based on key arthropod predators as action thresholds of the whitefly pest Bemisia tabaci MEAM1 (Dinsdale et al. 2010; equivalent to Bemisia argentifolii Bellows et al. 1994 [Hemiptera: Aleyrodidae]), validated their efficacy, and promoted them to cotton pest managers. This dissertation begins with a multi-year field trial where whitefly and natural enemy populations were manipulated with a series of insecticidal treatments to identify key arthropod predators. The critical abundance of four key predators necessary to suppress whiteflies was estimated through predator: prey ratios. These ratios were refined for commercial pest management and developed to conform to the current whitefly IPM framework as a simple to use management-decision tool that would be readily adopted and used by pest managers. Predator: prey ratios were then validated in 1) a second field trial, 2) commercial fields in Arizona and northern Mexico and 3) historical field trials conducted from 1997-2010, where whitefly management decisions made with the standard threshold and ratios, were compared with the standard threshold alone. I found no difference in management outcomes when decisions were made with the standard threshold alone, or with predator: prey ratios in the field trial, but analysis of potential decisions on commercial farms and with historical trial data indicated that the majority of sprays could be delayed if control decisions incorporated ratio-based thresholds. Finally, an outreach program was developed and deployed to present ratios as decision-making tools for cotton pest managers that reduce uncertainty in control decisions and optimize spray outcomes. Pest managers indicated positive changes in knowledge and a gradual adoption of ratios for decision-making. The implementation of whitefly control decisions that incorporate predator: prey ratios may reduce pest managers' uncertainty in decision-making, as well as insecticide use and management costs.