Thesis (M.S.)--Oregon State University, 2005. / Printout. Includes bibliographical references. Also available on the World Wide Web.

M.Sc. / The possible resistance of the red spider mite, Tetranychus cinnabarinus, on cotton to the acaricides triazophos and profenofos was studied in the Groblersdal/Marble Hall area. During the 1980 and 1981 seasons T. cinnabarinus was collected from cotton in four districts where mite infestations had been controlled the preceeding two seasons with up to three triazophos sprays per year. A laboratory culture of T. cinnabarinus served as the control and the response of these mites to different concentrations of acaricides were compared with those of the four field cultures. The toxicity of triazophos and profenofos was evaluated by using the slide-dip technique and mortality readings were taken 24 hours after exposure to the acaricide solutions. The data were subjected to a pro bit analysis. Where pro bit lines could not be fitted second degree polinomial regressions were fitted through the log dose and empirical probits. During 1980 there was little difference between the susceptibility of the four field cultures to triazophos. However, the regression lines of all four cultures when compared with those of the control culture indicated resistance to triazophos. After these field cultures had been reared under controlled conditions and not exposed to pesticides for a year all signs of triazophos resistance disappeared. The four field cultures collected in 1981 showed great variability in their response to triazophos but no indication of resistance was observed. This may be because the recommended cotton pest control programme was more closely followed by the cotton producers in 1981 and fewer acaricide sprays were applied. The accuracy of the mortality readings made 24 hours after exposure to triazophos was investigated by taking readings at intervals of 8 hours. An analysis of the results indicated that the mortality curves calculated from all readings were not significantly different and consequently mortality readings were made every 24 hours after exposure to the acaricide solution. A second laboratory strain of T. cinnabarinus, obtained from the Fruit and Fruit Technology Research Institute in Stellenbosch, and regarded as susceptible to organo phosphates was also tested for resistance to triazophos. The regression lines obtained for this culture was similar to that obtained from the 1980 field cultures. This was taken as an indication of possible resistance and this culture was therefore not used as a con trol in this study. The control culture and the Groblersdal/Marble Hall field cultures did not differ significantly in their susceptibility to profenofos. However, profenofos is not widely used for the control of T. cinnabarinus on cotton and these results indicate that it can still be used effectively for the control of T. cinnabarinus. A third acaricide, amitraz, was also examined to determine its effect on T. cinnabarinus. The slide-dip technique was found to be unsuitable for the determination of mite resistance to amitraz. This acaricide is slow acting and an observation interval longer than 24 hours is required to obtain the necessary mortality data. It is difficult to exclude the effects of starvation when the slide-dip technique is used for prolonged periods and consequently amitraz was not tested further. An alternative method for the effective evaluation of this acaricide must be developed. From this study no definite evidence of resistance of T. cinnabarinus in the Grtoblersdal/Marble Hall cotton growing area to triazophos or profenofos was found. It was concluded that both can still be used effectively in the control programme for mites on cotton.

Economic losses caused by the two spotted spider mite (Tetranychus urticae Koch) in the agricultural industry prompted the initiation of this project to evaluate the potential of native and exotic Beauveria bassiana isolates as biocontrol agents against this pest. Before the selection of a potential mycopesticide for use at a commercial scale, several crucial criteria must be taken into consideration. The application of some of these criteria have been the focus of this study and include: production of virulent B. bassiana inoculum, an evaluation of the virulence of the fungus against T. urticae, monitoring of the fungal infection cycle in T. urticae and establishing a phylogenetic evaluation of B. bassiana isolates using rDNA sequence analysis. A two-stage in vitro diphasic fermentation process produced B. bassiana inoculum. In the first submerged phase the impact of nutrient treatments (carbon and nitrogen) at different concentrations (3% and 4%) in a 1:1 ratio was investigated for mycelium dry mass production and spore yield. The 4% nutrient concentration yielded a higher mycelium dry mass yield compared to the 3% and was therefore used in the second semi-solid phase to stimulate aerial conidia formation in response to low nutrient stress. The fungal structures produced during the first phase of the diphasic fermentation process were submerged conidia recognized as small, spherical structures with a smooth form. In comparison, inoculum of the second semi-solid phase produced aerial conidia with small, spherical, rough surfaces and a brittle appearance assumed to be related to nutrient deprivation. Nutritional parameters exploited in this study favoured conidia production for use as a potential mycopesticide. An in vitro bioassay compared the infectivity of exotic and native isolates of B. bassiana against T. urticae adults. All the isolates were pathogenic with mite mortality increasing over time. Differences in the virulence of the B. bassiana isolates were demonstrated suggesting host-specificity. With respect to the native isolates B. bassiana (PPRI 04305) was more virulent than the B. bassiana sensu latu isolates (PPRI 04304 and PPRI 04306). The differences in the virulence of the native isolates are reflections of genetic differences demonstrated in the phylogenetic analyses in this study. The results of the preliminary bioassay study suggest that B. bassiana has the potential as a biocontrol agent of T. urticae. Microscopy was used to morphologically visualise the post infection cycle of a native B. bassiana isolate (PPRI 04305) in the two-spotted spider mite. The infection cycle observed in the current study is in agreement with those described in a number of agricultural pests. However, aspects not observed before with T. urticae infection included limited hyphal growth on the cuticle surface before penetration, per os mode of entry, cuticular melanization, lateral hyphal development under the cuticle and aerial hyphal emergence through the setal annulum on the dorsal surface of the cadaver. These observations will stimulate further research in the development of B. bassiana as a mycoacaricide. rDNA analysis of the ITS1-5.8S-ITS2 regions of different Beauveria species was assessed for strain genotyping and population studies. Fitch parsimony and neighbour joining analyses displayed species differentiation and confirmed that B. bassiana was not a monophyletic group but a species complex. Distinct clades in the phylogenetic analyses in the current study were matched to four species of Beauveria: B. bassiana, B. cf. bassiana, Beauveria brongniartii and Beauveria caledonica species. Two South African isolates PPRI 04304 and PPRI 04306 morphologically assigned to B. bassiana, are assumed to be either B. caledonica or a close relative of B. caledonica based on the rDNA analysis. However, due to the lack of confirmation of the change of species identification of these native isolates, they are regarded as B. bassiana sensu latu. Results from this study demonstrated the importance of rDNA analysis in biocontrol studies for population studies and species differentiation. The material in this dissertation highlighted some important characteristics relevant for the biocontrol of T. urticae by B. bassiana. Aerial conidia produced by the cost-effective diphasic fermentation process were virulent against T. urticae and demonstrated high percentage mortalities. B. bassiana was shown to be a generalist pathogen with strain-dependent differences in nutrient preferences and virulence against the mite. Differences in the infectivity of the native isolates B. bassiana (PPRI 04305) and B. bassiana sensu latu (PPRI 04304 and PPRI 04306) were reflections of the genotypic separation of the isolates demonstrated by rDNA analysis. The results obtained from this research project are promising for the ongoing research and development of Beauveria isolates as efficient mycoacaricides against T. urticae for the South African agricultural market.

M.Sc. / The extent of economic damage caused to the cotton variety Acala 1517/70 by the feeding activities of Tetranychus cinnabarinus (Boisduval) has been studies at the Loskop Research Station, situated in the Transvaal Middleveld. Special attention is given to the relative importance of the occurrence of spider mite infestations during the various stadia in the development of the cotton plant. the common method by which the extent of mite infestations is calculated, namely the conversion of adult female counts to female-days / leaf is used, and this unit of measure is compared to the percentage of leaf surface area over which visible damage extends (trial 1) as well as to the actual damaged leaf surface area. An index system is used to determine the percentage of leaf surface area over which visible damage extends (trial 1). The effectiveness of this procedure in determining the actual damaged leaf surface area is found to be sufficient, and is recommended as it appears to be a rapid and accurate method for evaluation during field trials. In accordance with quoted literature it is determined that the regression of both the leaf surface area over which damage extends (as determined by the index system as described) and the actual damaged leaf surface area against the female-days I leaf at a specific stage, are highly significant. It is confirmed that the use of either the percentage of leaf surface area over which damage extends or the actual damaged leaf surface area is valid. A method that is based on the use of female-days) leaf, but which in addition takes into account the stage (in days after planting) at which a particular spider mite count has been present is developed for the purposes of this study. It has been confirmed that this particular unit (damagedays IleaO has practical application value. It is pointed out that even in the early stages of population buildup there exists a highly significant relationship between both the femaledays / leaf and the damage-days Ileaf,and the yield masses. Significant reductions of up to 16 percent in yield were found in spite of the fact that notable spider mite infestations had not occurred prior to the flowering peak. By taking the value of the cotton yield into account and comparing it with the cost of control, an economic evaluation of the specific treatments is made. The following important conclusions were reached: • The confirmation of the profitability of applying an acaricide (triazophos) as soon as the first signs of a red spider mite infestation is discovered. • the irrelevance of programme spraying regardless of the infestation present, • the decrease in relative importance of red spider mide infestations in the later stages of the development of the cotton plant, and • the probability of spider mites affecting both the yield mass and quality if heavy infestations prevail after 19 weeks (133 days) after planting.

No description available.

La araña roja, Tetranychus urticae Koch (Acari: Tetranychidae) es una de las plagas más perjudiciales que afectan los huertos de clementinos en España. En los clementinos, T. urticae habita en el envés de las hojas, donde produce tela y colonias densas. Absorbe el contenido de las células, causando manchas cloróticas en el lado superior de las hojas. Al final del ernao T. urticae puede provocar en los frutos icatrices características y en consecuencia, pérdida de su valor comercial. Hasta la fecha, el control de T. urticae se ha basado, principalmente, en el control químico. sin embargo, este método no es siempre eficaz. Los artrópodos beneficiosos se eliminan, y se crean condiciones favorables para la proliferación incontrolada de T. urticae y otras plagas. En la actualidad, los programas de gestión integrada de plagas en cítricos, tienen como objetivo maximizar el uso de control biológico. en este sentido, el objetivo general de esta tesis ha sido la mejora del control biológico de T. urticae en los huertos de clementinos. El control biológico no es común en los viverso de cítricos donde el coontrol químico es frecuente. El neonicotinoide sistémico imidacloprid aplicado vía riego es eficaz contra tres de las cujatro principales plagas de plantones de clementino en España - áfidos, minador y cocchinillas. Sin embargo, los ácaros, la cuarta-la plaga clave, no se controlan con imidacloprid, pero podrían regularse mediante sueltas de los ácaros depredadores fitoseidos Phytoseiulus persimilis Athias-Henriot y Neoseiulus californicus (McGregor). El objetivo de este estudio fue evaluar los efectos de imidacloprid aplicado vía riego en los parámetros demográficos de P. persimilis se vieron afectados por imidacloprid. Sin embargo, su efecto combinado sobre la tasa intrínseca de incremento fue neutro. Por el contrario, imidacloprid afectó negativamente los parámetros demográficos de N. californicus. Los resultados de campo demostraron que los plantones dfe clementino podría / Sá Argolo, P. (2012). Gestión Integrada de la araña roja Tetranychus urticae Koch (Acari: Tetranychidae): optimización de su control biológico en clementinos [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17804

Gorse, Ulex europaeus, is a serious weed of agriculture and forestry in New Zealand. The mite Tetranychus lintearius feeds on gorse in Europe and was released in New Zealand during autumn 1989 as a potential biological control agent. The aim of my laboratory study was to increase available knowledge on its development and aggregation. As the quality of gorse declined as a food resource (as indicated by chlorophyll content) a significant decline in egg production, and an increase in development time of mites was found. Mean egg production at 15℃ ranged from 37.8 to 45.2 eggs/female over 10 days in the experimental treatments and development time from 39.2 to 43.3 days. Density of adult female mites (1, 2, 5, 10, 15, 20/spine) also had a significant effect on the number of eggs produced/female over ten days (mean daily egg production/female, 0.78-0.88). Mean development time from egg to adult decreased from 40.6 to 39 days as density increased from 1 to 50 mites/spine. The resident New Zealand strain of T lintearius, imported originally from Cornwall, is now widely established but has not established successfully on the west coast of the South Island or in the north of the North Island. Four new strains recently introduced from coastal Portugal and Spain, areas climatically similar to these New Zealand regions, may be more successful. Thus, although egg production and survival of all strains were significantly reduced when subjected to daily periods of simulated rainfall in laboratory experiments, those of the newly introduced strains were least affected. Laboratory experiments with the resident New Zealand and Cambados strains also showed that individuals aggregated actively at 10-20℃, but the latter aggregated more strongly at these temperatures. This strong aggregation behaviour may increase survival in warm, wet climates and suggests that Cambados strain mites could become established and so increase gorse control in Westland and Northland.

Submitted by Ana Paula Lisboa Monteiro (monteiro@univates.br) on 2010-03-23T14:43:53Z No. of bitstreams: 1 CarlaEichelberger.pdf: 3108008 bytes, checksum: 299a283cea58942fd42b4daf2bd06b5f (MD5) / Made available in DSpace on 2010-03-23T14:43:53Z (GMT). No. of bitstreams: 1 CarlaEichelberger.pdf: 3108008 bytes, checksum: 299a283cea58942fd42b4daf2bd06b5f (MD5) / Apesar da grande importância da cultura do pêssego no Rio Grande do Sul, pouco se conhece sobre a acarofauna, diversidade e flutuação populacional de ácaros nesta cultura, assim como sobre aspectos socioambientais relativos aos processos produtivos de pêssegos, o que se verifica a partir dos modos de fazer de produtores e técnicos envolvidos nesta produção. O objetivo deste estudo foi conhecer a acarofauna associada a cultura do pêssego, nos municípios de Roca Sales e Venâncio Aires nas cultivares Premier e Eldorado, respectivamente; e analisar a diversidade e a flutuação de ácaros, identificando os discursos dos atores envolvidos para compreender como interferem nos seus modos de produção. Para identificação e caracterização dos discursos dos produtores e os atores com os quais estes interagem foram realizadas entrevistas semi-estruturadas. Para conhecer a acarofauna, diversidade e flutuação populacional de ácaros no pessegueiro foram realizadas avaliações mensais no período de julho de 2008 a junho de 2009, quando foram amostradas 15 plantas escolhidas aleatoriamente numa área em cada município. As plantas foram divididas em quadrantes e de cada quadrante foi escolhido um galho de onde foram retiradas três folhas, sendo uma coletada no terço apical, outra no terço médio e a última no terço basal, totalizando 180 folhas por área. No momento da coleta das folhas de pêssego também foram coletadas partes de cinco plantas invasoras mais comuns. Foram encontrados 1124 ácaros pertencentes a 28 espécies de 14 famílias. Maior abundância de ácaros foi observada em Venâncio Aires, com 77% dos ácaros. Tetranychidae foi a família mais abundante 895 espécimes, sendo 827 pertencentes à Tetranychus ludeni (Zacher, 1913) que foi a principal espécie herbívora coletada nos dois municípios, sendo mais encontrada de novembro a janeiro, com pico populacional em dezembro, precedido por meses com baixas precipitações e umidade relativa, seguido de Panonychus ulmi (Koch, 1836) encontrado somente na cultivar Eldorado. Aculus fockeui (Nalepa, 1898) (Eriophyidae) foi o único eriofídeo encontrado, com 45 espécimes. Entre os predadores Phytoseiidae apresentou maior riqueza com oito espécies, sendo quatro delas presentes nas duas áreas avaliadas. Typhlodromalus aripo (DeLeon, 1967) foi mais abundante com maiores populações nas plantas invasoras em ambos os municípios. Em relação à análise dos discursos dos produtores e técnicos pode-se verificar que em Roca Sales a diversificação de culturas é maior, também percebeu-se aí um produtor que utiliza mais agrotóxicos químicos e trabalha associado a uma empresa, Girelli de Bento Gonçalves. Neste município o técnico da Emater demonstrou estar mais a parte, auxiliando o produtor somente se necessário. Enquanto em Venâncio Aires a inserção de novas culturas, como o pêssego, é barrada muitas vezes pelas dificuldades impostas pela administração pública, a qual apóia com mais incentivos a cultura do fumo. Neste município o técnico da Emater é mais presente e, mesmo com todos estes empecilhos, o produtor tenta utilizar na sua produção de pêssegos somente agrotóxicos orgânicos.

Submitted by Ana Paula Lisboa Monteiro (monteiro@univates.br) on 2013-05-31T16:42:05Z No. of bitstreams: 3 MarlizaReichery.pdf: 1438506 bytes, checksum: b612dc9309b070f8dd2d2b36b911d54f (MD5) license_text: 20502 bytes, checksum: 3eba3066a10168f04bd5d83d74ca6c40 (MD5) license_rdf: 22392 bytes, checksum: da4b2e8e72d470a5e1afe4c26352b4ac (MD5) / Made available in DSpace on 2013-05-31T16:42:05Z (GMT). No. of bitstreams: 3 MarlizaReichery.pdf: 1438506 bytes, checksum: b612dc9309b070f8dd2d2b36b911d54f (MD5) license_text: 20502 bytes, checksum: 3eba3066a10168f04bd5d83d74ca6c40 (MD5) license_rdf: 22392 bytes, checksum: da4b2e8e72d470a5e1afe4c26352b4ac (MD5) / A soja é a cultura que mais cresceu nos últimos anos, sendo ela importante economicamente para o Brasil e para o Rio Grande do Sul. A soja está sujeita ao ataque de diferentes espécies de herbívoros que podem se transformar em pragas. As pragas da soja podem causar perdas significativas no rendimento da cultura e, por isso, necessitam ser controladas. Este estudo avaliou a acarofauna associada à cultura da soja na Região Noroeste do Estado do Rio Grande do Sul nos municípios de Mato Queimado e Três de Maio. As avaliações foram realizadas em soja convencional, em soja transgênica com irrigação e sem irrigação e com tratamentos fitossanitários diferenciados e em plantas de borda. As atividades de campo foram realizadas na safra 2011/2012. As coletas foram realizadas quinzenalmente onde a cada coleta eram escolhidas vinte plantas de soja, das quais foram retiradas três folhas/planta, totalizando 60 folhas/área. As folhas foram coletadas nas regiões basal, mediana e apical da planta. A cada coleta de folhas de soja também foram coletadas cinco espécies de plantas de borda. As folhas de soja e as plantas de borda foram individualizadas em sacos plásticos, guardadas sob- refrigeração até serem processadas. Os ácaros foram retirados de ambas as faces das folhas e montados em lâminas para a identificação. Foi encontrado na soja um total de 18.100 ácaros pertencentes a cinco famílias, nove gêneros e 12 espécies distintas, além dos ácaros da Subordem Oribatida. A área de soja transgênica com irrigação e aplicação de inseticida apresentou a maior riqueza e abundância, com 10 espécies e um total de 8.329 ácaros, seguida pela área com soja transgênica sem irrigação, com aplicação de inseticida com nove espécies e 4.901 ácaros. Menor riqueza foi observada na área transgênica sem irrigação e sem aplicação de inseticida com cinco espécies. A área com menor abundância foi a de soja convencional sem aplicação de inseticida com 1.091 ácaros. Phytoseiidae apresentou maior riqueza, com cinco espécies, seguida de Tetranychidae, com quatro espécies, Iolinidae, Stigmaeidae e Tarsonemidae. Dentre os ácaros fitófagos mais frequentes e abundantes na soja, destacaram-se Tetranychus urticae Koch, Mononychellus planki McGregor e Tetranychus spp. Os ácaros predadores mais abundantes foram Neoseiulus idaeus Denmark & Muma, Pseudopronematus sp., Neoseiulus californicus McGregor e Neoseiulus anonymus Chant & Baker respectivamente. Neoseiulus idaeus também foi à espécie mais frequente. Nas plantas de borda foram encontrados um total de 576 ácaros, sendo N. idaeus e Agistemus sp. os ácaros predadores mais abundantes.

Gorse, Ulex europaeus, is a serious weed of agriculture and forestry in New Zealand. The mite Tetranychus lintearius feeds on gorse in Europe and was released in New Zealand during autumn 1989 as a potential biological control agent. The aim of my laboratory study was to increase available knowledge on its development and aggregation. As the quality of gorse declined as a food resource (as indicated by chlorophyll content) a significant decline in egg production, and an increase in development time of mites was found. Mean egg production at 15℃ ranged from 37.8 to 45.2 eggs/female over 10 days in the experimental treatments and development time from 39.2 to 43.3 days. Density of adult female mites (1, 2, 5, 10, 15, 20/spine) also had a significant effect on the number of eggs produced/female over ten days (mean daily egg production/female, 0.78-0.88). Mean development time from egg to adult decreased from 40.6 to 39 days as density increased from 1 to 50 mites/spine. The resident New Zealand strain of T lintearius, imported originally from Cornwall, is now widely established but has not established successfully on the west coast of the South Island or in the north of the North Island. Four new strains recently introduced from coastal Portugal and Spain, areas climatically similar to these New Zealand regions, may be more successful. Thus, although egg production and survival of all strains were significantly reduced when subjected to daily periods of simulated rainfall in laboratory experiments, those of the newly introduced strains were least affected. Laboratory experiments with the resident New Zealand and Cambados strains also showed that individuals aggregated actively at 10-20℃, but the latter aggregated more strongly at these temperatures. This strong aggregation behaviour may increase survival in warm, wet climates and suggests that Cambados strain mites could become established and so increase gorse control in Westland and Northland.