Historically, most twospotted spider mite, Tetranychus urticae Koch, infestations occurred during the late season near maturity, but since 2005, infestations of cotton have become more common throughout the entire season. Several factors may have contributed to the increasing frequency of mites in seedling cotton, one of which is a shift in production practices from furrow applied aldicarb to neonicotinoid seed treatments for thrips control. Another factor that may impact T. urticae densities in seedling cotton is a shift from pre-plant tillage to conservation tillage or no-till cropping systems. Although the literature confirms that T. urticae can cause extensive cotton yield losses, there is a need to further refine potential late-season yield loss. From 2007 to 2009 a series of experiments were conducted to address these issues. In a series of 12 field experiments, neonicotinoid seed treatments resulted in twospotted spider mite densities greater than those in the untreated check, aldicarb, and acephate treatments. Untreated check and aldicarb treatments had the lowest mite densities. Only aldicarb controlled mites compared to the untreated check. A twospotted spider mite host survey determined that henbit, Lamium amplexicaule L., was the most consistent and preferred host. Carolina geranium, Geranium carolinianum L., cutleaf geranium, Geranium dissectum L., vetch, Vicia spp., volunteer soybean, Glycine max L., purple deadnettle, Lamium purpureum L., and spiny sowthistle, Sonchus asper (L.) Hill, were other frequently infested dicotyledonous species. Herbicide burndown timing in reduced tillage cotton production was not critical, given all weeds were killed before cotton was planted. The herbicide glufosinate was efficacious against T. urticae, providing control equal to low- to mid-rates of labeled acaricides. Including glufosinate in a herbicide burndown program was only beneficial for mite control if living weeds were present at planting. Artificial infestation experiments were adversely affected by unseasonably wet and cool weather. Infestations established at the third true leaf resulted in an average yield loss of 44.7%. It is difficult to make any conclusions about infestations made from first bloom and later because of the difficulty in establishing mite populations later in the season.

The twospotted spider mite, Tetranychus urticae Koch, is a serious pest of many ornamental plants (Johnson and Lyon, 1991). Pesticide resistance, the high cost of pesticides and loss of production time have raised interest by growers to introduce predatory phytoseiid mites to manage twospotted spider mites and reduce their need for acaricide applications (Sabelis, 1981). The predatory mite Phytoseiulus persimilis Athias-Henriot has been used successfully in integrated pest management programs for T. urticae suppression. Despite the success of P. persimilis in reducing populations of T. urticae, acaricide applications may still necessary due to limitations associated with the effectiveness of P. persimilis introductions. The objectives of this study were to; 1. Measure the effects of acaricides on the density and age structure of T. urticae populations. 2. Determine the compatibility of acaricides in an IPM program by measuring the toxicity of residues to P. persimilis and T. urticae adults. 3. Study the feeding behavior of P. persimilis on T. urticae. 4. Measure the effects of combinations of acaricides followed by release of P. persimilis on T. urticae populations using greenhouse trials. The effects of ten acaricides on T. urticae populations were measured on infested Buddleia x davidii 'White Profusion' cuttings. Acaricides did not alter age structure in predictable manner. Initial analysis of results demonstrates that cuttings treated with acaricides had age structures that were different from control treatments. However, these differences were not distinguishable from natural fluctuations in the age structure. Chlorfenapyr may have changed the age structure of T. urticae. Azadirachtin, pyridaben and spinosad did not suppress T. urticae populations at the rates and formulations tested in this trial. Abamectin, bifenthrin, chlorfenapyr, Gowan 1725,oil and neem oil suppressed T. urticae populations. Hexythiazox suppressed T. urticae populations but these results were not seen until two weeks after application. The effects of acaricide residues were tested on adult P. persimilis and T. urticae 1, 3, 7, and 14 days after application using a leaf disk system. Abamectin, Gowan 1725, hexythiazox, horticultural oil, neem oil, pyridaben and spionsad were not toxic to P. persimilis adults while bifenthrin and chlorfenapyr residues were toxic to P. persimilis. Tetranychus urticae mortality from chlorfenapyr residues was significantly greater than the control 1,3,7 and 14 days after application. Tetranychus urticae mortality from bifenthrin and abamectin residues was significantly greater than the control 3, 7, and 14 days after application. Tetranychus urticae mortality caused by Gowan 1725, horticultural oil, and neem oil residues was significantly greater than the control 1 day after application, while mortality from hexythiazox and spinosad residues was not significantly greater than the control at any of the times tested in this study. Phytoseiulus persimilis feeding behavior studies examining life stage preference tests and functional response studies were conducted on bean leaf disks. We found P. persimilis functional response to be a type II response for both eggs and adults with handling times of 0.079 hours for eggs and 3.399 hours for adults. The effects of a combination of acaricides followed by release of P. persimilis on T. urticae populations was tested using greenhouse studies conducted on infested Buddleia plants. In the first trial, severe plant damage occurred despite a reduction in the mean number of mites per leaf in treatments with oil+ predator treatments 7 days after release. Results from the second greenhouse trial produced plants with less visual damage compared to those in the first greenhouse trial. Treatments with predators alone and predators + acaricides produced similar results. However, treatments with predators had a mean numbers of mites per leaf that were significantly less than treatments with acaricides alone. The results demonstrate that the acaricides tested in the second greenhouse trial allowed the predators to provide suppression of T. urticae populations. A high release rate was used in the second greenhouse trial and lower release rates as well as different acaricide predator combinations need be tested to explore the possibility of new management techniques. Our results suggest that the number of pest mites present in the crop may be the most important factor affecting the success of biological control with predators. Combinations of oil applications followed by introduction of P. persimlis 3 days after release provided suppression of T. urticae populations in a meaningful time frame. I was not able to shape the age structure of T. urticae populations in a predictable manner with acaricide applications. Phytoseiulus persimilis does not have a prey-stage preference when feeding on T.urticae, but the shorter handling time for eggs may indicate that they are better able to suppress populations with higher proportions of eggs. However, we cannot determine if P. persimilis can keep T. urticae populations composed of predominately of eggs below threshold levels because our greenhouse trials did not test this hypothesis. Phytoseiulus persimilis feeding on adult T. urticae may suppress T. urticae populations below threshold levels because a reduction in the number of adults will lead to a reduction in the number of T. urticae eggs deposited on a plant. Our research suggests that abamectin and oil are two acaricides that would be less detrimental to the survival of P. persimilis. Additional greenhouse trials with compatible acaricides should be conducted as well as research on the threshold density of T. urticae that will allow P. persimilis to provide adequate control. / Master of Science

The aims of this study were to develop a detailed record of the tetranychid mites of Kenya and Tanzania, to assess the diversity of tetranychid mites in the east African biodiversity hotspots and to determine female characters that can be used to identify the species of the economically important Tetranychus species found in these countries. The genetic diversity of the most abundant Tetranychus species (Tetranychus evansi Baker & Pritchard) was also assessed. The Tetranychidae (Acari) contain some of the most important pest species of phytophagous mites worldwide. Out of the almost 1,300 species in this family, 256 species are known to occur in Africa. Before this study, ten species had been reported from Kenya and only three in Tanzania. The genus Tetranychus to which most of the pest species belongs to, can only be identified to species level by the use of the male aedeagus that is often difficult to visualize. The natural habitat, the Eastern Arc Mountains and East African Coastal Forests in Kenya and Tanzania is recognized as biodiversity hotspots but prior to his study, information on Tetranychidae in these hotspots was lacking. Thus, no information on the natural mite fauna composition was available. In Kenya, 18 tetranychid mite species from various plant hosts have been recorded. Four of these species belong to the subfamily Bryobiinae and the other 14 to the subfamily Tetranychinae. Eight of the mite species identified belong to the genera Bryobia, Petrobia, Peltanobia, Paraplonobia, Duplanychus, Eutetranychus and Mixonychus and are being reported for the first time in Kenya while the other ten had already been reported before. For Tanzania, six species belonging to the genera Tetranychus, Eutetranychus and Mixonychus are being reported for the first time from Tanzania and other three had been reported before. A list of these species, their brief descriptions as well as a key for identification is provided. A redescription of Peltanobia erasmusi including previously undescribed male characters is given. Schizotetranychus kwalensis sp. nov. from Kenya and Brevinychus meshacki from Tanzania were collected on Omorcarpum kirkii (Fabaceae) from Matuga, Kwale district, Kenya and Philonoptera eriocalyx (Fabaceae) from Sangasanga, Mvomero district, Tanzania respectively and described. Revised keys of Brevinychus and of the African species of Schizotetranychus are also provided. Tetranychus evansi Baker & Pritchard ranked highest in abundance amongst all the tetranychid mites collected. It was found in four out of five fragments of the hotspot, and it survives in a wide range of altitudes from as low as 123 m to 1655 m. Molecular examination of T. evansi collected from Kenya and Tanzania and on different host plants revealed an identical DNA sequence of the mitochondrial COI fragment and 19 identical microsatellite alleles suggesting a single introduction of this species to this part of East Africa. Female characters of four Tetranychus species found in Kenya were explored using the scanning electron microscope. Differences in the distances between the duplex setae of species belonging to the desertorum group (Tetranychus evansi Baker & Pritchard and Tetranychus ludeni Zacher) and those grouped by Flechtmann and Knihinicki (2002) under group 9 (Tetranychus neocaledonicus Andre and Tetranychus urticae Koch) were observed. The dorsal striae of T. evansi, T. neocaledonicus and T. urticae have semicircular lobes whereas those on the dorsal striae of T. ludeni are triangular. / Thesis (PhD (Environmental Sciences))--North-West University, Potchefstroom Campus, 2012.

The aims of this study were to develop a detailed record of the tetranychid mites of Kenya and Tanzania, to assess the diversity of tetranychid mites in the east African biodiversity hotspots and to determine female characters that can be used to identify the species of the economically important Tetranychus species found in these countries. The genetic diversity of the most abundant Tetranychus species (Tetranychus evansi Baker & Pritchard) was also assessed. The Tetranychidae (Acari) contain some of the most important pest species of phytophagous mites worldwide. Out of the almost 1,300 species in this family, 256 species are known to occur in Africa. Before this study, ten species had been reported from Kenya and only three in Tanzania. The genus Tetranychus to which most of the pest species belongs to, can only be identified to species level by the use of the male aedeagus that is often difficult to visualize. The natural habitat, the Eastern Arc Mountains and East African Coastal Forests in Kenya and Tanzania is recognized as biodiversity hotspots but prior to his study, information on Tetranychidae in these hotspots was lacking. Thus, no information on the natural mite fauna composition was available. In Kenya, 18 tetranychid mite species from various plant hosts have been recorded. Four of these species belong to the subfamily Bryobiinae and the other 14 to the subfamily Tetranychinae. Eight of the mite species identified belong to the genera Bryobia, Petrobia, Peltanobia, Paraplonobia, Duplanychus, Eutetranychus and Mixonychus and are being reported for the first time in Kenya while the other ten had already been reported before. For Tanzania, six species belonging to the genera Tetranychus, Eutetranychus and Mixonychus are being reported for the first time from Tanzania and other three had been reported before. A list of these species, their brief descriptions as well as a key for identification is provided. A redescription of Peltanobia erasmusi including previously undescribed male characters is given. Schizotetranychus kwalensis sp. nov. from Kenya and Brevinychus meshacki from Tanzania were collected on Omorcarpum kirkii (Fabaceae) from Matuga, Kwale district, Kenya and Philonoptera eriocalyx (Fabaceae) from Sangasanga, Mvomero district, Tanzania respectively and described. Revised keys of Brevinychus and of the African species of Schizotetranychus are also provided. Tetranychus evansi Baker & Pritchard ranked highest in abundance amongst all the tetranychid mites collected. It was found in four out of five fragments of the hotspot, and it survives in a wide range of altitudes from as low as 123 m to 1655 m. Molecular examination of T. evansi collected from Kenya and Tanzania and on different host plants revealed an identical DNA sequence of the mitochondrial COI fragment and 19 identical microsatellite alleles suggesting a single introduction of this species to this part of East Africa. Female characters of four Tetranychus species found in Kenya were explored using the scanning electron microscope. Differences in the distances between the duplex setae of species belonging to the desertorum group (Tetranychus evansi Baker & Pritchard and Tetranychus ludeni Zacher) and those grouped by Flechtmann and Knihinicki (2002) under group 9 (Tetranychus neocaledonicus Andre and Tetranychus urticae Koch) were observed. The dorsal striae of T. evansi, T. neocaledonicus and T. urticae have semicircular lobes whereas those on the dorsal striae of T. ludeni are triangular. / Thesis (PhD (Environmental Sciences))--North-West University, Potchefstroom Campus, 2012.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Under natural conditions, plants release volatile organic compounds (VOCs) that can differ either qualitative or quantitatively from those induced by herbivory. Induced VOCs are specific, varying with the attacked plant species, with the herbivore, and the developmental stages and conditions from both species. Induced VOCs mediate important ecological interactions. They can attract predators and parasitoids, repel herbivores and mediate communication between neighboring plants and different parts of the same plant. Cassava (Manihot esculenta) is a native plant from Brazil cultivated in all regions, but mainly in the northeast region. It has an important role in animal and human feeding, manufacturing of industrial products and the creation of jobs and income. Several studies have been conducted to identify the volatile compounds induced by herbivory and observe their influence in the behavior of herbivores and their natural enemies, however, to date little is known about the VOCs emissions of cassava plants and their role in arthropod-plant interactions. This study aimed at identifying the volatiles induced by herbivory from the herbivorous mites Mononychellus tanjoa, Tetranychus urticae and T. gloveri in cassava plants, and how these herbivorous mites and the predatory mite Neoseiulus idaeus respond to induced VOCs blends. Twenty three compounds (monoterpenes, sesqueterpenes, aldehyde, alcohol, esters, oxime, phenylpropanoid and indole) were identified in the headspace of healthy and mite-damaged cassava plants. Herbivore-damaged plants released novel compounds that weren’t emitted by the healthy plants. Significant difference were found in the emission of methyl salicylate by M. tanajoa and T. gloveri infested plants, and (Z)-3-hexen-1-ol infested with T. urticae, when compared to healthy plants. The compounds (Z)-β-ocimene, 2-methyl propanol oxime, 2-methyl butanoloxime, indole, methyl anthranilate and (E)-nerolidol were only induced by herbivory from T. urticae, and may be involved in the attraction of N. idaeus, since the predator with experience in cassava significantly preferred plants infested with T. urticae compared to healthy plants. Tetranychus gloveri with cassava experience preferred healthy cassava plants compared to clean air, demonstrating that the plant produces volatiles that are attractive to herbivores. It can be concluded that after the herbivory cassava plants emit VOCs that differ qualitatively and quantitatively from those released by healthy plants and the total amount emitted increases with the density of mites in the plant. Despite the emission of VOCs known to attract predatory mites by plants infested with M. tanajoa and T. gloveri, N. idaeus did not prefer infested plants, suggesting that the level of induction was not sufficient or these herbivorous mites are not attractive to the predator. / As plantas constantemente liberam um conjunto de compostos orgânicos voláteis (COVs) para a atmosfera que pode diferir qualitativa e quantitativamente dos voláteis que são liberados quando são atacadas por herbívoros. A composição desses voláteis é específica, variando de acordo com a espécie de planta e do herbívoro, e com os estágios de desenvolvimento e condições dessas espécies. Os COVs são importantes na mediação de interações específicas, podendo atrair predadores e parasitoides, repelir herbívoros e mediar a comunicação entre plantas vizinhas e diferentes partes de uma mesma planta. A mandioca, Manihot esculenta, é uma planta nativa do Brasil, sendo cultivada em todas as regiões, destacando-se a região Nordeste, com importante papel na alimentação humana e animal, como matéria-prima para produtos industriais e geração de emprego e renda. Diversos estudos têm sido realizados com o objetivo de identificar os COVs induzidos por herbivoria e observar a sua influência no comportamento dos herbívoros e seus inimigos naturais, porém pouco se sabe sobre as emissões de COVs das plantas de mandioca e seu papel nas interações artrópodes-plantas. No presente estudo buscou-se identificar os voláteis induzidos pela herbivoria dos ácaros Mononychellus tanajoa, Tetranychus urticae e T. gloveri em plantas de mandioca, e como esses ácaros herbívoros e o ácaro predador Neoseiulus idaeus respondem aos conjuntos de COVs induzidos. Foram identificados 23 compostos (monoterpenos, sesquiterpenos, aldeídos, álcool, oximas, éster, indole e fenilpropanoide) liberados pelas plantas de mandioca sadias e submetidas à herbivoria. Plantas com herbivoria emitiram novos compostos que não foram liberados pelas plantas sadias. Foi encontrada diferença significativa na emissão de salicilato de metila pelas plantas com herbivoria de M. tanajoa e T. gloveri, e (Z)-3-hexen-1-ol pelas plantas com herbivoria de T. urticae, quando comparadas com as plantas sadias. Os compostos (Z)-β-ocimeno, 2-metil propanol oxima, 2-metil butanol oxima, indole, metil anthranilate e (E)-nerolidol foram induzidos apenas pela herbivoria de T. urticae e podem estar envolvidos na atração de N. idaeus, uma vez que o predador com experiência em mandioca preferiu significativamente as plantas infestadas com T. urticae em comparação às plantas sadias. Tetranychus gloveri com experiência em mandioca preferiu plantas de mandioca sadias em comparação ao ar limpo, demonstrando que a planta produz voláteis atraentes para os herbívoros. Pode-se concluir que após a herbivoria plantas de mandioca emitem COVs que diferem qualitativa e quantitativamente daqueles liberados pelas plantas sadias e a quantidade total emitida aumenta com a densidade de ácaros na planta. Apesar da emissão de COVs conhecidos por atraírem ácaros predadores pelas plantas infestadas com M. tanajoa e T. gloveri, N. idaeus não preferiu as plantas infestadas, sugerindo que o nível de indução não foi suficiente ou esses ácaros herbívoros não são atraentes para o predador.

A major goal of evolutionary developmental biology is to explore mechanisms and events underlying evolution of the myriad body plan morphologies expressed both genetically and phenotypically within the animal kingdom. Arthropods exhibit an astounding array of morphological diversity both within and between representative sub-phyla, thus providing an ideal phylum through which to address questions of body plan innovation and diversification. Major arthropod groups are recognised and defined by the distinct form and number of articulated appendages present along the antero-posterior axis of their segmented bodies. A great deal is known about the developmental genetics of limb development in the model insect Drosophila melanogaster, added to which, much comparative gene expression data and a growing body of functional genetic data is emerging for other arthropod species. Arthropod limb primordia are consistently marked by expression of the homeobox gene Distal-less (Dll), and the focus of this thesis is to compare signalling mediated by early Dll regulatory genes activity along antero-posterior and dorso-ventral embryonic axes during limb specification in Drosophila, with the activity of their orthologs in the widely disparate chelicerate, the spider mite Tetranychus urticae - interpreting new data with that available for other arthropods. Having made a detailed study of spider mite embryonic (and post-embryonic) development, to provide a basis for understanding mRNA transcription and protein activity patterns, I confirmed typical expression of Tetranychus Dll in prosomal limb primordia. I obtained limited results for the candidate antero-posterior positioning genes wingless and engrailed, although one of the two engrailed paralogs I identified is reportedly expressed in posterior segmental compartments, consistent with possible conservation of Engrailed-Wingless interactions in metameric patterning and positive regulation of Dll in arthropod limb specification. In Drosophila, wingless-dependent Dll transcription is restricted along the dorso-ventral axis by dorsal Dpp-mediated and ventral EGFR-mediated signalling gradients. Based on data from Tetranychus and other arthropods, neither dorsal nor ventral signalling regimes appear conserved outside the Drosophila system. Dll suppression in fly abdominal segments occurs due to powerful Hox (Ubx/AbdA) repression of the early Dll cis-regulatory element; this is discussed in relation to the independently evolved limbless chelicerate opisthosoma, informed by hypothetical scenarios of cis (regulatory DNA) and trans (coding sequence) evolution. Given practical difficulties and limitations encountered while working with spider mites, I offer a final assessment of the place of Tetranychus urticae as a non-model, and yet still valuable chelicerate species to consider carrying into the exciting future of evolutionary developmental biology.

O cultivo de flores iniciou-se no Brasil como atividade econômica em maior escala a partir de 1960. Atualmente, cerca de 5.000 produtores dedicam-se à floricultura em todo país. O setor gera um faturamento estimado em U$ 400 milhões/ano. No varejo, o faturamento é estimado em U$ 1,3 bilhões/ano. Acredita-se que a floricultura brasileira gera atualmente entre 120 a 160 mil empregos, caso seja considerada toda a cadeia produtiva que envolve o campo, a distribuição, o comércio varejista e os segmentos de apoio. O ácaro rajado, Tetranychus urticae Koch, é uma das principais pragas em plantas ornamentais, com destaque para o cultivo de gérberas e roseiras. O uso excessivo de acaricidas para o controle desta praga tem trazido sérios problemas ao ambiente e à saúde humana. Diversos trabalhos têm mostrado o potencial dos ácaros predadores da família Phytoseiidae para o controle de T. urticae. Alguns parecem ser promissores no controle daquela praga, sendo Neoseiulus californicus (McGregor) um deles. No Brasil, não há nenhuma informação sobre o potencial deste predador em cultivos comerciais de gérberas e roseiras. O objetivo do presente trabalho foi: estabelecer estratégias de manejo de T. urticae em cultivos de gérberas e roseiras; estabelecer um sistema de criação massal de N. californicus; determinar o ciclo de vida de duas espécies de ácaros predadores que pudessem ser eventualmente utilizadas em futuros estudos ou estratégias de manejo de pragas daquelas culturas. Uma metodologia para estimar a densidade populacional de T. urticae sobre Canavalia ensiformis (L.) DC foi determinada (para sistemas de criação massal de ácaros predadores) através da contagem de T. urticae em 3 regiões de 1 cm2 cada (base, meio e ápice). A maior precisão na determinação do número total de ácaros na folha foi obtida através da estimativa dos ácaros na região basal e do somatório das 3 regiões [coeficiente de determinação (r2) = 0, 63 e 0,85, respectivamente]. O sistema de produção massal de N. californicus mostrou-se satisfatório. A partir de uma estrutura simples e com um custo relativamente baixo foi possível produzir até 300.000 ácaros predadores a cada 15 dias nos períodos mais quentes do ano. Em relação às tabelas de vida dos predadores estudados, Proprioseiopsis cannaensis (Muma) e Neoseiulus barkeri Hughes não completaram o desenvolvimento quando alimentados com Phyllocoptruta oleivora (Ashmead). Os valores de rm de P. cannaensis foram -0,05, -0,09 e 0,002 alimentado com Brevipalpus phoenicis (Geijskes), T. urticae e pólen de Typha angustifolia L, respectivamente. Os valores de rm de N. barkeri foram -0,03, 0,139 e 0,141, alimentado com B. phoenicis, T. urticae e pólen, respectivamente. N. barkeri parece ter potencial no controle de ácaros Tetranychidae, embora situações de campo devam ser testadas. Em relação às liberações de N. californicus em cultivos de gérberas e roseiras, os resultados foram altamente satisfatórios. Além de menor impacto ambiental, a utilização deste predador associada às aplicações de acaricidas seletivos mostrou-se uma alternativa eficiente e economicamente viável no controle de T. urticae. / Flower growing on a large scale as an economic activity in Brazil started in 1960. Currently, approximately 5.000 farmers practice floriculture in the whole country. The sector generates an estimated income of U$ 400,000/year. Retail income is estimated at US$ 1.3 billions/year. It is currently believed that Brazilian flower industry generates between 120 and 160 thousand employment opportunities if all the productive chains are considered which involve field work, distribution, retail sales and support segments. The two spotted spider mite, Tetranychus urticae Koch, is one of the principal pests of ornamental plants and prominently attacking gerberas and roses. The excessive use of acaricides for the control of this pest poses serious problems on the environment and human health. Several studies have demonstrated the potential of predatory mites from the family Phytoseiidae in the control of T. urticae. Some of these predators seem to be promising for the control of this pest among them Neoseiulus californicus (McGregor). In Brazil, information about the potential of this predator in commercial crops of gerberas and roses is lacking. The objective of the current work was: establish management strategies of T. urticae in gerbera and rose flowers; establish a mass rearing system for N. californicus; determine the life cycle of the two predatory mite species that could be used in future studies or management strategies for pests on these crops. A method for estimating population density of T. urticae on Canavalia ensiformis (L.) DC was determined (for mass rearing system of predatory mites) through counting of T. urticae in 3 regions of 1 cm2 each (bottom, middle and apex). The highest precision in the determination of the total number of mites on leaves was obtained through mite estimates at the basal region and the summations of the 3 regions [coefficient of determination (r2) = 0. 63 and 0.85, respectively]. The mass production system of N. californicus was shown to be satisfactory. Starting with a simple structure and with a relatively low cost, it was possible to produce up to 300.000 predatory mites every 15 days during the hottest period of the year. In relation to the life tables of the studied predators, Proprioseiopsis cannaensis (Muma) and Neoseiulus barkeri Hughes did not complete their development when fed on Phyllocoptruta oleivora (Ashmead). The rm values of P. cannaensis were -0.05, -0.09 and 0.002 when fed on Brevipalpus phoenicis (Geijskes), T. urticae and pollen of Typha angustifolia L, respectively. The rm values of N. barkeri were -0.03, 0.139 and 0.141, when fed on B. phoenicis, T. urticae and pollen, respectively. N. barkeri seem to have potential for the control of tetranychid mites, however, field conditions should be tested. In relation to release of N. californicus in gerbera and rose flowers, the results were highly satisfactory. In addition to lower environmental impact, the use of this predator in combination with selective acaricides shows an efficient and economically viable alternative for the control of T. urticae.

O ácaro-vermelho do tomateiro, Tetranychus evansi Baker e Pritchard, tornou-se a praga mais importante do tomateiro, e de outras solanáceas na África, após a sua introdução naquele continente. Não se conhece nenhum inimigo natural nativo efetivo em associação com a praga na África, tornando necessária a busca de inimigos naturais em sua região de origem. T. evansi não é uma importante praga em grande parte da na América do Sul, sugerindo que este ácaro provavelmente tenha se originado nesta região. Buscas por inimigos naturais realizadas nesta região resultaram na coleta de diversos isolados de Neozygites floridana Weiser e Muma e do ácaro predador Phytoseiulus longipes Evans com potencial para introdução na África. Como parte das etapas preliminares, para introdução deste fungo patogênico na África, estudos foram conduzidos para determinar a compatibilidade de N. floridana com P. longipes, pois é desejável que estes dois inimigos naturais se complementem. Foi demonstrado que o fungo não é patogênico a P. longipes. O único efeito do fungo observado em P. longipes foi o incremento do comportamento de auto-limpeza (grooming) para remoção de capiloconídios do fungo aderidos ao corpo do ácaro. Alguns agrotóxicos empregados na produção de tomate foram testados quanto aos seus efeitos sobre N. floridana, a fim de determinar a seletividade e a adequação destes para uso em programas de MIP em tomateiro. Dois inseticidas, dois acaricidas e dois fungicidas foram testados em duas concentrações: a dosagem comercial recomendada (TC) e metade da dosagem comercial (TC / 2). Os fungicidas captana and mancozebe afetaram a esporulação e a germinação de N. floridana em ambas as concentrações, enquanto propargito não teve efeito sobre a esporulação, mas afetou a germinação dos conídios primários. Metomil e abamectina foram os produtos com menores efeitos sobre N. floridana. Adicionalmente, o efeito de plantas hospedeiras de T. evansi sobre N. floridana foi determinado em relação à contaminação, infecção, mortalidade e mumificação. A oviposição de T. evansi foi usada para determinar a adequação dos ácaros às plantas hospedeiras e esta foi correlacionada com a suscetibilidade dos ácaros ao fungo e subseqüente mumificação. O efeito dos aleloquímicos acumulados pelos ácaros sobre o fungo foi avaliado acompanhando-se o desenvolvimento da doença em ácaros que haviam sido criados nas diferentes plantas hospedeiras, mas que foram infectados e mantidos até a morte em tomate. Houve uma associação direta entre a oviposição, adequação de T. evansi às plantas hospedeiras medido pela taxa de oviposição e os parâmetros de desempenho avaliados do fungo, exceto para T. evansi sobre maria-preta e T. urticae sobre pimenta e algodão. A oviposição foi baixa onde, também, a esporulação foi baixa, sugerindo que a antibiose da planta pode afetar tanto a reprodução do ácaro como a atividade do fungo. A mortalidade e a mumificação variaram com a espécie de planta, provavelmente, indicando que estes processos são modulados pela composição química da planta. O efeito da temperatura sobre a esporulação, infecção e mumificação dos ácaros foi comparado entre três isolados de N. floridana, dois do Brasil (de Recife e de Piracicaba) e um da Argentina (Vipos-Tucumán) objetivando selecionar isolados potenciais para liberar em diferentes locais na África. Estes parâmetros foram avaliados sob vários regimes de temperatura constantes entre 13ºC e 33ºC. Também foi avaliado o efeito de seis regimes de temperaturas alternadas, 17-13°C, 21-13°C, 29-13°C, 33-13°C, 33-23°C, 33-29°C, sob fotoperíodo de 12:12h, luz e escuro, respectivamente, sobre a virulência dos três isolados contra T. evansi. Os perfis de temperatura em conjunto com os dados de infectividade podem ser úteis na seleção de isolados apropriados para uma determinada região com características térmicas particulares. / The tomato red spider mite, Tetranychus evansi Baker and Pritchard, became one of the most important pests of tomatoes and other solanaceous plants in Africa after its introduction in this continent. No native natural enemies are known to be associated with the pest in Africa making search for natural enemies necessary. T. evansi is not an important pest in South America suggesting that this mite probably originated from this region. Searches for natural enemy in this region yielded several isolates of Neozygites floridana Weiser and Muma and one potential predatory mite for introduction in Africa. As part of the preliminary steps for introduction of this fungal pathogen in Africa, studies were conducted to determine the compatibility of N. floridana with the predatory mite Phytoseiulus longipes Evans, because the two natural enemies are expected to complement each other. It was demonstrated that the fungus is not pathogenic to P. longipes. However, the presence of fungal capilliconidia on the leaf may alter the behavior of P. longipes by increasing grooming. Several pesticides used in tomato production were tested for their effect on N. floridana in order to determine their selectivity and adequacy for use in IPM programs for pest management in tomato. Two insecticides, two acaricides, and two fungicides were tested in two concentrations: the mean commercial rate (CR) and 50% of the mean commercial rate (CR/2). The fungicides Captan and Mancozeb affected sporulation and germination at both concentrations while Propargite had no effect on sporulation but affected germination of primary conidia. Methomyl and Abamectin had minimal effects on N. floridana. In addition, the effect of host plants of T. evansi on N. floridana was determined in relation to contamination, infection, mortality and mummification. Oviposition was used to determine host plant suitability to the mites and this was correlated to their susceptibility and subsequent mummification after infection by the fungus. Host-switching was used to determine the in vivo effect of accumulated allelochemicals to the fungus. There was a direct association of oviposition, plant suitability and the measured fungal parameters on all host plants with the exception of nightshade and pepper for T. evansi and cotton for T. urticae. Oviposition was also low on plants where sporulation was low suggesting that antibiosis may affect both mite reproduction and fungal activity. Mortality and mummification varied with plant species probably indicating that this processes are modulated by plant chemistry. The effects of temperature on sporulation, infection and mummification of mites was compared among three isolates of N. floridana, two from Brazil (from Recife and Piracicaba) and one from Argentina (Vipos-Tucumán) aiming to select potential isolates for release in different places of Africa. These parameters were measured at various constant temperature regimes from 13°C to 33°C. Six alternating temperature regimes of 17-13°C, 21-13°C, 29-13°C, 33-13°C, 33-23°C, 33-29°C at a photoperiod of 12:12h light and dark, respectively were also used to test their effect on the virulence of the three isolates against T. evansi. Temperature profiles in conjunction with infectivity assays can be useful in selecting appropriate isolates for a particular thermal environment.

At present, the global population is increasing, while soil and fresh water resources for crop production are declining. It is important to adopt sustainable practices to optimise the use of limited natural resources without compromising the environment, and to enhance continuous production in the long term. The rapid growth of UK strawberry industry has been achieved through the precision use of varieties, nutrients and polythene tunnels. This intensive production has caused significant environmental impacts especially Greenhouse Gas (GHG) emissions from the production. Strawberry powdery mildew (Podosphaera aphanis) is a major fungal disease affecting strawberry production worldwide particularly in polythene tunnels. The disease can result in yield losses of up to 70% of the crop. A ruleQbased system was used in the field trials to predict high risk days of P. aphanis development, taking into account the optimal environmental conditions conducive to conidial germination and disease development. The results (Chapter 3) showed that the use of this prediction system achieved satisfactory control of P. aphanis in commercial strawberry production, with reduced fungicide applications compared with commercial spray programme. The results were consistent in two consecutive years and on different varieties. In addition, it was suggested that the use of the prediction system may also lead to lower GHG emissions associated with fewer fungicide applications, thereby benefit strawberry growers both environmentally and economically. Results from 2014 & 2015 silicon fertigation trials showed that the use of a silicon nutrient via the fertigation system reduced the strawberry susceptibility to P. aphanis and twoQspotted spider mites (Tetranychus urticae Koch) in two consecutive years on different varieties (Chapter 4). In both years, crops received the silicon nutrient only without fungicides had both lower rate of epidemic (r) and lower value of Area Under the Disease Progress Curve (AUDPC) (r = 0.0036, AUDPC = 475 in 2014; r = 0.001, AUDPC = 267 in 2015) compared with the untreated control (r = 0.0042, AUDPC = 662 in 2014; r = 0.0011, AUDPC = 281 in 2015). Silicon also delayed the epidemic buildQup in the silicon nutrient only treatment for approximately two weeks compared with the untreated control. Crops from the silicon nutrient plus fungicides treatment had lower susceptibility (r = 0.0012 in 2014; r = 0.0004 in 2015) than those from the fungicides only treatment (r = 0.0017 in 2014; r = 0.0005 in 2015) suggesting that the silicon nutrient may also enhance fungicides performance in reducing the epidemic buildQup when used together. Moreover, the presence of T. urticae on strawberry leaves was significantly lower (P < 0.001) in plants treated with the silicon nutrient than those without. In addition, initial results suggested that silicon may play a positive role in raising °Brix of strawberry leaf petiole, improving pollen viability, and influencing the length of flower receptacle and stamens. Maltmas Farm has a wide range of semiQnatural habitats that provide food and nesting resources for wild pollinators. Hoverflies, bumblebees and solitary bees were found to be the main wild pollinators that pollinate commercial strawberries at Maltmas Farm (Chapter 5). The number of pollinators in tunnels or open fields significantly correlated with the abundance of strawberry flowers (P < 0.05). Pollinator presence also differed between groups throughout the day and over the seasons. Hoverflies appeared early in the day and were abundant in summer months; bumblebees and solitary bees were present most of the day and throughout the season, whereas honeybees were only active in sunny days. Temperatures, relative humidity and cloud coverage also affected pollinator presence. In addition, pollinator activity was not significantly (P > 0.05) affected by the application of the silicon nutrient via the fertigation system. The integrated use of the prediction system (to reduce fungicide applications and subsequent GHG emissions), the silicon nutrient (to reduce crop susceptibility to P. aphanis and T. urticae), and sustainable farmland management (to encourage the presence of wild pollinators) could help strawberry growers to achieve a more sustainable production.

O cultivo de flores iniciou-se no Brasil como atividade econômica em maior escala a partir de 1960. Atualmente, cerca de 5.000 produtores dedicam-se à floricultura em todo país. O setor gera um faturamento estimado em U$ 400 milhões/ano. No varejo, o faturamento é estimado em U$ 1,3 bilhões/ano. Acredita-se que a floricultura brasileira gera atualmente entre 120 a 160 mil empregos, caso seja considerada toda a cadeia produtiva que envolve o campo, a distribuição, o comércio varejista e os segmentos de apoio. O ácaro rajado, Tetranychus urticae Koch, é uma das principais pragas em plantas ornamentais, com destaque para o cultivo de gérberas e roseiras. O uso excessivo de acaricidas para o controle desta praga tem trazido sérios problemas ao ambiente e à saúde humana. Diversos trabalhos têm mostrado o potencial dos ácaros predadores da família Phytoseiidae para o controle de T. urticae. Alguns parecem ser promissores no controle daquela praga, sendo Neoseiulus californicus (McGregor) um deles. No Brasil, não há nenhuma informação sobre o potencial deste predador em cultivos comerciais de gérberas e roseiras. O objetivo do presente trabalho foi: estabelecer estratégias de manejo de T. urticae em cultivos de gérberas e roseiras; estabelecer um sistema de criação massal de N. californicus; determinar o ciclo de vida de duas espécies de ácaros predadores que pudessem ser eventualmente utilizadas em futuros estudos ou estratégias de manejo de pragas daquelas culturas. Uma metodologia para estimar a densidade populacional de T. urticae sobre Canavalia ensiformis (L.) DC foi determinada (para sistemas de criação massal de ácaros predadores) através da contagem de T. urticae em 3 regiões de 1 cm2 cada (base, meio e ápice). A maior precisão na determinação do número total de ácaros na folha foi obtida através da estimativa dos ácaros na região basal e do somatório das 3 regiões [coeficiente de determinação (r2) = 0, 63 e 0,85, respectivamente]. O sistema de produção massal de N. californicus mostrou-se satisfatório. A partir de uma estrutura simples e com um custo relativamente baixo foi possível produzir até 300.000 ácaros predadores a cada 15 dias nos períodos mais quentes do ano. Em relação às tabelas de vida dos predadores estudados, Proprioseiopsis cannaensis (Muma) e Neoseiulus barkeri Hughes não completaram o desenvolvimento quando alimentados com Phyllocoptruta oleivora (Ashmead). Os valores de rm de P. cannaensis foram -0,05, -0,09 e 0,002 alimentado com Brevipalpus phoenicis (Geijskes), T. urticae e pólen de Typha angustifolia L, respectivamente. Os valores de rm de N. barkeri foram -0,03, 0,139 e 0,141, alimentado com B. phoenicis, T. urticae e pólen, respectivamente. N. barkeri parece ter potencial no controle de ácaros Tetranychidae, embora situações de campo devam ser testadas. Em relação às liberações de N. californicus em cultivos de gérberas e roseiras, os resultados foram altamente satisfatórios. Além de menor impacto ambiental, a utilização deste predador associada às aplicações de acaricidas seletivos mostrou-se uma alternativa eficiente e economicamente viável no controle de T. urticae. / Flower growing on a large scale as an economic activity in Brazil started in 1960. Currently, approximately 5.000 farmers practice floriculture in the whole country. The sector generates an estimated income of U$ 400,000/year. Retail income is estimated at US$ 1.3 billions/year. It is currently believed that Brazilian flower industry generates between 120 and 160 thousand employment opportunities if all the productive chains are considered which involve field work, distribution, retail sales and support segments. The two spotted spider mite, Tetranychus urticae Koch, is one of the principal pests of ornamental plants and prominently attacking gerberas and roses. The excessive use of acaricides for the control of this pest poses serious problems on the environment and human health. Several studies have demonstrated the potential of predatory mites from the family Phytoseiidae in the control of T. urticae. Some of these predators seem to be promising for the control of this pest among them Neoseiulus californicus (McGregor). In Brazil, information about the potential of this predator in commercial crops of gerberas and roses is lacking. The objective of the current work was: establish management strategies of T. urticae in gerbera and rose flowers; establish a mass rearing system for N. californicus; determine the life cycle of the two predatory mite species that could be used in future studies or management strategies for pests on these crops. A method for estimating population density of T. urticae on Canavalia ensiformis (L.) DC was determined (for mass rearing system of predatory mites) through counting of T. urticae in 3 regions of 1 cm2 each (bottom, middle and apex). The highest precision in the determination of the total number of mites on leaves was obtained through mite estimates at the basal region and the summations of the 3 regions [coefficient of determination (r2) = 0. 63 and 0.85, respectively]. The mass production system of N. californicus was shown to be satisfactory. Starting with a simple structure and with a relatively low cost, it was possible to produce up to 300.000 predatory mites every 15 days during the hottest period of the year. In relation to the life tables of the studied predators, Proprioseiopsis cannaensis (Muma) and Neoseiulus barkeri Hughes did not complete their development when fed on Phyllocoptruta oleivora (Ashmead). The rm values of P. cannaensis were -0.05, -0.09 and 0.002 when fed on Brevipalpus phoenicis (Geijskes), T. urticae and pollen of Typha angustifolia L, respectively. The rm values of N. barkeri were -0.03, 0.139 and 0.141, when fed on B. phoenicis, T. urticae and pollen, respectively. N. barkeri seem to have potential for the control of tetranychid mites, however, field conditions should be tested. In relation to release of N. californicus in gerbera and rose flowers, the results were highly satisfactory. In addition to lower environmental impact, the use of this predator in combination with selective acaricides shows an efficient and economically viable alternative for the control of T. urticae.