Clover root curculio (CRC) is a pest of alfalfa where larvae feed belowground damaging alfalfa roots. Regional knowledge of CRC activity and biology is limited making the development of pest management strategies difficult. One potential management technique for soil-dwelling pests is the use of biofumigant containing cover crops. Biofumigation can affect the survival and behavior of pest insects. However, biofumigant crops have not been evaluated against CRC or as a rotational crop compatible with alfalfa. The goals of this research were to determine 1) phenology, population sizes, and root damage severity of CRC occurring in the Intermountain region and 2) the direct and indirect suppressive effects of biofumigant cover crop incorporations on CRC and its agronomic compatibility in rotation with alfalfa. First, I observed that larval activity occurred from mid-spring to mid-summer and local larval densities were generally lower than those reported in the eastern U.S. Adult CRC began emerging from the soil in mid-summer having two population peaks. After the second fall peak of adults was when most eggs were deposited which continued through early winter. CRC damage to taproots was cumulative, increasing as stands age, with most damage occurring in the first few years of stand life and mostly occurring in the top 20 cm of roots. While the incorporation of biofumigant crops appeared to be compatible with alfalfa and did not negatively affect yield, in field trials, biofumigation did not suppress CRC, disrupt egg laying, or decrease feeding damage. In one greenhouse trial, biofumigants significantly suppressed adult feeding rates more than non-biofumigant plants but the effect was not consistent. Biofumigant incorporation timing, for field trials in particular, may have contributed to the lack of CRC suppression. Overall, my research provides a better understanding of CRC phenology and activity in northern Utah and will assist in improving the timing of management approaches in alfalfa.

Biofumigation is an important crop protection practice that uses a plant’s natural defence mechanisms to control agricultural crop pathogens and diseases. Glucosinolates are volatile compounds found in most Brassica species and when hydrolysed, it forms a range of natural toxins including isothiocyanates that act as biofumigants. Research suggests that biofumigation is a good alternative to chemical fumigants as it is effective in controlling plant pests but with lower health and environmental risks. Several studies have confirmed the effectiveness of the breakdown products, especially isothiocyanates, as fungicidal, bactericidal and nematicidal products against a series of plant pests. However, very little information is available on the effects of glucosinolates and its breakdown products on non-target and beneficial soil organisms. Negative effects on beneficial soil organisms can have serious negative impacts on soil quality especially when essential ecosystem functions such as nutrient cycling and soil bioturbation are affected. Three biofumigants, broccoli, mustard and oilseed radish, and two chemical fumigants, metham sodium and cadusafos, were investigated for possible effects on non-target and essential soil organisms such as earthworms and the soil microbial community. Sublethal endpoints, including growth and reproductive success of the earthworms, were monitored. The genotoxicity of the biologically active compounds found in the fumigants, towards earthworms, was evaluated by means of the comet assay. The DNA damage was quantified by tail intensity parameters. Furthermore, the changes in the soil microbial community function and structure were evaluated by means of community level physiological profiling (CLPP) and phospholipid fatty acid (PLFA) analyses respectively. All exposures were done in artificial soil prepared according to the OECD standard guidelines. In the biofumigant treated soils, results varied and different effects were observed on the non-target soil organisms. Broccoli reduced cocoon production and the number of hatchlings while mustard induced more DNA strand breaks in earthworm cells compared to the control. All the biofumigants stimulated microbial growth but broccoli and oilseed radish changed the microbial functional diversity. Mustard had no lasting effect on the functional diversity but altered the microbial community structure. The chemical fumigants had a marked negative impact on the survival, growth, reproduction and the genotoxicity of the earthworms with metham sodium causing greater harm than cadusafos. The effects on the microbial community varied. Both chemicals had an inhibitory effect on the microbial growth in terms of the viable biomass determined by PLFA and the average well colour development in the Biolog™ Ecoplates. No lasting effects were observed in the community structure. Overall, cadusafos had a more pronounced effect on the microbial community functional diversity than metham sodium. Results indicated that each bioindicator species illustrates effects at their own level of organisation / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Biofumigation is an important crop protection practice that uses a plant’s natural defence mechanisms to control agricultural crop pathogens and diseases. Glucosinolates are volatile compounds found in most Brassica species and when hydrolysed, it forms a range of natural toxins including isothiocyanates that act as biofumigants. Research suggests that biofumigation is a good alternative to chemical fumigants as it is effective in controlling plant pests but with lower health and environmental risks. Several studies have confirmed the effectiveness of the breakdown products, especially isothiocyanates, as fungicidal, bactericidal and nematicidal products against a series of plant pests. However, very little information is available on the effects of glucosinolates and its breakdown products on non-target and beneficial soil organisms. Negative effects on beneficial soil organisms can have serious negative impacts on soil quality especially when essential ecosystem functions such as nutrient cycling and soil bioturbation are affected. Three biofumigants, broccoli, mustard and oilseed radish, and two chemical fumigants, metham sodium and cadusafos, were investigated for possible effects on non-target and essential soil organisms such as earthworms and the soil microbial community. Sublethal endpoints, including growth and reproductive success of the earthworms, were monitored. The genotoxicity of the biologically active compounds found in the fumigants, towards earthworms, was evaluated by means of the comet assay. The DNA damage was quantified by tail intensity parameters. Furthermore, the changes in the soil microbial community function and structure were evaluated by means of community level physiological profiling (CLPP) and phospholipid fatty acid (PLFA) analyses respectively. All exposures were done in artificial soil prepared according to the OECD standard guidelines. In the biofumigant treated soils, results varied and different effects were observed on the non-target soil organisms. Broccoli reduced cocoon production and the number of hatchlings while mustard induced more DNA strand breaks in earthworm cells compared to the control. All the biofumigants stimulated microbial growth but broccoli and oilseed radish changed the microbial functional diversity. Mustard had no lasting effect on the functional diversity but altered the microbial community structure. The chemical fumigants had a marked negative impact on the survival, growth, reproduction and the genotoxicity of the earthworms with metham sodium causing greater harm than cadusafos. The effects on the microbial community varied. Both chemicals had an inhibitory effect on the microbial growth in terms of the viable biomass determined by PLFA and the average well colour development in the Biolog™ Ecoplates. No lasting effects were observed in the community structure. Overall, cadusafos had a more pronounced effect on the microbial community functional diversity than metham sodium. Results indicated that each bioindicator species illustrates effects at their own level of organisation / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Il est encore difficile de prédire et de contrôler le développement des maladies telluriques qui sont à l'origine de nombreux dégâts dans les systèmes de culture. Ce travail interdisciplinaire en épidémiologie a pour objectif de comprendre et de modéliser le développement spatio-temporel des épidémies telluriques afin d'identifier des leviers de gestion pour ces maladies. En se basant sur le pathosystème betterave sucrière - Rhizoctonia solani, la thèse se focalise sur trois problèmes. Dans un premier temps, en alliant mesures expérimentales de la dispersion du pathogène et simulations d'un modèle stochastique spatialement explicite, nous montrons que la croissance de l'hôte peut induire un changement dans le comportement du système qui, dans certains cas, devient invasif alors qu'il était initialement non-invasif. Dans un second temps, sur la base de mesures expérimentales nous proposons un modèle âge-dépendant de la distribution de la période d'incubation qui est utilisé pour relier les infections cachées et les observations de maladie. Le comportement cryptique des épidémies est ensuite étudié par simulation d'un modèle spatial hiérarchique qui intègre la période d'incubation. Dans un troisième temps, un modèle spatialement implicite est utilisé pour estimer les taux d'infection à partir de données temporelles de maladie et pour analyser les effets de la biofumigation sur les épidémies. Ces paramètres sont ensuite utilisés pour prédire le développement stochastique des épidémies à partir d'un modèle spatial individu-centré. Les résultats confirment que la biofumigation ne permet qu'un contrôle partiel des épidémies mais suggèrent que ce contrôle biologique diminue l'incertitude autour du développement cryptique de la maladie. Pour finir, les résultats de ces travaux sont discutés et les perspectives qu'ils suscitent sont présentées.

Kentucky is the nation’s leading producer of burley tobacco and the crop’s most economically important disease is black shank, caused by Phytophthora nicotianae (Pn). Current management is effective, however, problems with expense and pathogen persistence are issues. Two alternative methods for control of Pn were examined: biofumigation and soil application of an organic, yeast fermentation‐derived product (Soil‐Set). Field studies in 2009 and 2010 found no effect on populations of fungi, disease severity of Pn, and yield between mustard‐ and wheat‐amended plots. Experiments in the greenhouse suggested that survival of Pn was impacted by biomass rather than biofumigation. Biofumigation is not a viable option for controlling black shank in tobacco production. Soil‐Set was inhibitory against mycelial growth of Pn on corn meal agar rather than V8 juice. Results from a greenhouse study indicated that increasing the dose of Soil‐Set by four times what is recommended held the most potential for suppression of Pn in a burley variety with no resistance. A field study in 2012 found no differences among treatments in reducing severity of Pn in a variety with high resistance. More field and greenhouse studies need to be conducted to examine the potential of Soil‐Set in tobacco production.

The banana is a major fruit grown by small and medium producers in the state of Alagoas. Most plantations are located in the region of forest and coastline, with favorable conditions for the development of diseases. This study aimed to make the lifting of the diseases in areas of the banana plantation of Alagoas and evaluate the alternative control of moko (Ralstonia solanacearum). The first stage was conducted during the years 2006 and 2007, making up visits and collection of plant material infected in 60 areas producing of banana, fourteen municipalities in the state. The material collected was subjected to procedures for identification of pathogens associated with plants. Detaching to the diseases caused by fungi and nematodes, and identified Yellow Sigatoka (Pseudocercospora musae); Deightoniella spot (Deightoniella torulosa) and Cordana spot (Cordana musae), a widespread occurrence; Chloridium spot (Chloridium musae), only in areas with shading and combined with other leaf spots; Exosporella spot, observed in Santana do Mundaú; fitonematoses caused by Rhadophulus similis, Helicotylenchus multicinctus and Pratylenchus sp., detected only in some municipalities; Panama disease (Fusarium oxysporum f.sp. cubense ) Found in four areas in the south of the state and Moko (R. solanacearum), in three areas. The alternative control of moko was the second stage of work, bearing in mind the significant losses that this disease causes the production of bananas. In the first experiment, isolates of rizobactérias were confronted, in the BDA, with a isolated of R. solanacearum, the method of streaks and incubated at 28 º C for 72 hours. Isolates RAB7, C110, C25, R14, HLT2, HRT4 and C11 induced a significant reduction in the growth of R. solanacearum. The bacteria selected in vitro were tested in the Banana plantlets, which had its roots wounds and immersed in the suspension of bacteria (108 cfu / mL) for a period of 20 minutes. Then, the seedlings were transplanted into pots with sterile substrate and incubated in a greenhouse, for 48 hours, when infestation of the substrate with a suspension of R. solanacearum (108 cfu / mL). According to statistical analyses the isolated RAB7 proved to be an interesting bacterial antagonist, followed by isolated C110, C25 and HLT2. In the second experiment, initially, it was evaluated different concentrations of essential oils of citronela, eucalyptus citriodora, clove and ginger: 1.25%, 3.5%, 3.75% and 5% and extracts of clove, ginger, cinnamon and melon (são-caetano): 5%, 10%, 15% and 20%, measuring up the halo of inhibition of bacteria after 48 hours of assembly of the experiment. The treatments involving eucalyptus oil and extracts of melon of San Caetano, clove and cinnamon did not differ from the witness. The extract of ginger, oils of citronela, clove and ginger differed significantly the level of 5%, inhibiting the growth of R. solanacearum, in all concentrations tested, stressing that the oil of clove, followed by extracts of ginger. Banana plantlets trees were sprayed with concentrations that showed better performance in vitro: oils of citronela, clove and ginger (3.75%) and extract of ginger (20%) up to 10 ml / plant. Eight days after the plantlets were inoculated with the pathogen (108 cfu / mL). The citronela oil provided the best result, with 100% control of the disease, however, caused fitotoxidez the plants. The oil and ginger extract, were similar in effectiveness to control moko (50%), oil and clove had lower efficiency (25%). In the third experiment, were tested organic residues, 10 and 20% (v / v): cassava raspas, shellfish gravels, chicken litter, banana leaves and ginger. In vitro, cassava raspas (10%) reduced the number of colonies and halos of inhibition. Significant results were further observed with ginger 20%, shellfish gravels, banana leaves (10 and 20%). In the experiment "in vivo" the substrate sterilized was infested with the pathogen (108 cfu / mL), mixed waste selected in vitro and incubated for 20 days. Banana plantlets were transplanted in pots with the treatments. Ginger and banana leaves (10%) had low rates of infection of the plants (25%) while the shellfish gravels (10 and 20%) presented, respectively, 75 and 50% symptoms of wilt. / Fundação de Amparo a Pesquisa do Estado de Alagoas / Doenças da bananeira (musa spp.) no estado de Alagoas e controle alternativo do moko (Ralstonia solanacearum (Smith) Yabuuchi et al.). A banana é uma das principais frutas cultivadas por pequenos e médios produtores no estado de Alagoas. A maioria dos plantios está localizada na zona da mata e litoral, com condições favoráveis ao desenvolvimento de doenças. Este trabalho teve como objetivos realizar o levantamento das doenças da bananeira em áreas de plantio de Alagoas e avaliar o controle alternativo do moko (Ralstonia solanacearum). A primeira etapa foi conduzida durante os anos de 2006 e 2007, fazendo-se visitas e coleta de material vegetal infectado em 60 áreas produtoras de banana, em quatorze municípios do estado. O material coletado foi submetido a procedimentos para identificação dos patógenos associados às plantas. Destacaram-se as doenças causadas por fungos e nematóides, sendo identificadas a sigatoka amarela (Pseudocercospora musae); a mancha de Deightoniella (Deightoniella torulosa); a mancha de Cordana (Cordana musae), todas de ocorrência generalizada; a mancha de Chloridium (Chloridium musae), somente em áreas com sombreamento excessivo e associada a outras manchas foliares; a mancha de Exosporella (Exosporella sp.) observada em baixa freqüência; as fitonematoses causadas por Rhadopholus similis, Helicotylenchus multicinctus e Pratylenchus sp., detectado apenas em alguns municípios; o mal do Panamá (Fusarium oxysporum f. sp. cubense) encontrado somente em quatro áreas no sul do estado e o moko (Ralstonia solanacearum), em três áreas.O controle alternativo do moko constituiu a segunda etapa do trabalho, tendo em vista as perdas significativas que esta doença provoca na produção da banana. No primeiro experimento, isolados de bactérias foram confrontados, em meio BDA, com um isolado de R. solanacearum, pelo método de estrias e incubados a uma temperatura de 28ºC durante 72 horas. Os isolados RAB7, C110, C25, R14, HLT2, HRT4, C11 induziram uma significativa redução do crescimento de R. solanacearum. As bactérias selecionadas in vitro foram testadas em mudas de bananeira, que tiveram suas raízes feridas e imersas na suspensão bacteriana (108 cel/mL), por um período de 20 minutos. Em seguida, as mudas foram transplantadas para vasos com substrato esterilizado e incubadas em casa de vegetação, por 48 horas, quando ocorreu a infestação do substrato com uma suspensão de R. solanacearum (108 cel/mL). De acordo com as análises estatísticas o isolado RAB7 mostrou-se um antagonista bacteriano, seguidos pelos isolados C110, C25 e HLT2. O isolado R14 apresentou a menor porcentagem de redução da severidade da doença. No segundo experimento, inicialmente, foram avaliadas diferentes concentrações de óleos essenciais de citronela, eucalipto citriodora, cravo-da-índia e gengibre: 1,25%; 3,5%; 3,75% e 5% e de extratos de cravo-da-índia, gengibre, canela e melão de São Caetano: 5%, 10%, 15% e 20%, medindo-se o halo de inibição da bactéria após 48 horas. O óleo de eucalipto e os extratos de melão-de-são-caetano, cravo-da-índia e canela não diferiram da testemunha. O extrato de gengibre, os óleos de citronela, de cravo e de gengibre diferiram significativamente da testemunha, inibindo o crescimento de R. solanacearum,em todas as concentrações testadas, destacando-se o óleo de cravo como o melhor tratamento, seguido por extrato de gengibre. Mudas de bananeira foram pulverizadas com as concentrações que apresentaram melhor desempenho in vitro: óleos de citronela e cravo (3,75%), óleo de gengibre (3,75%) e extrato de gengibre (20%), aplicando-se 10 ml da solução por planta. Oito dias após, as mudas foram inoculadas com o patógeno (108 cel/mL). O óleo de citronela proporcionou o melhor resultado, com 100% de controle da doença, porém as folhas das plantas com esse tratamento apresentaram sintomas de fitotoxidez. O óleo e o extrato de gengibre foram semelhantes na eficiência de controle do moko (50%), e o óleo de cravo apresentou menor eficiência (25%). No terceiro experimento foram testados os resíduos orgânicos raspas de mandioca, cascalhos de marisco, cama-de-frango, folhas de bananeira e gengibre nas concentrações de 10 e 20 % v/v. O melhor resultado foi observado no tratamento com raspas de mandioca 10 % com redução no número de colônias e presença de maior número de halos de inibição. Resultados significativos foram, ainda, observados nos tratamentos com gengibre 20% e cascalho de marisco e folhas de bananeira (10 e 20%), onde também houve aparecimento de halos de inibição. No experimento in vivo o substrato esterilizado foi infestado com o patógeno (108 cel/mL), misturado aos resíduos, secos e triturados, selecionados in vitro e incubado por 20 dias, em sacos de polietileno. Mudas de bananeira foram transplantadas para vasos com os tratamentos. Nos substratos contendo raspas de gengibre (10%) e folhas de bananeira (10%v/v) as plantas apresentaram baixos índices de infecção (25%) enquanto que nos tratamentos com cascalhos de marisco (10 e 20 %v/v) apresentaram, respectivamente, 75 e 50% de sintomas de murcha, demonstrando que houve diferença entre as dosagens. O tratamento com raspas de mandioca não diferiu da testemunha, com 100% das mudas apresentando sintomas de murcha e morte.

The cowpea, Vigna unguiculata (L.) Walp., is known as feijão-de-corda and feijão-verde , among others, is one of the main cultures exploited by small producers of the Northeast region of Brazil. Among the phytopathogens that affects its productivity, Sclerotium rolfsii Sacc. is noteworthy, causing the stem rot in several cultures around the world. The objective of this work was to evaluate the alternative control of S. rolfsii Sacc. in saplings of V. unguiculata (L.) Walp. trough the biocontrol of antagonists, organic residues incorporation to the soil, utilization of essential oils, plant extracts and mineral nutrition. The work was developed in the Laboratory de Phytopathology and in the vegetation house of CECA/UFAL. The pathogen was obtained trough the isolations of cowpea with symptoms of the disease and, afterwards, it was cultivated in sterilized rice. For in vitro control, the antagonists isolates were matched with the pathogen in PDA medium, for the purpose of evaluating the reduction of growth and the hyperparasitism. For the biofumigations of the soil, the organic materials poultry litter, mussel, sugar cane bagasse, bean residue, cassava scuff were dehydrated in stove at 55ºC for 96h, grinded in the concentrations of 10% and 20% (v/v) and incorporated to the substrate, infested for 20 days and compared to the group treated with methyl thiophanate and to the control. After thirty days, the seedlings were evaluated about the incidence and the suppression of the disease. In the in vivo control the seeds were microbiolized with antagonists (C110, C21, ENF24, R14 and Trichoderma harzianum), the fungicide and saline solution for the control. The substrate was infested with the pathogen, two days after the sow, and after 30 days were evaluated. For the natural substances, 21 days old seedlings were pulverized with cassava flour wastewater extract (40%), eucalyptus oil (1%), peppermint (1%), Ecolife® (2%), methyl thiophanate (0,7 g/L) and water for the control and after two days, the substrate was infested with the pathogen. Six days after the inoculation, a new pulverization was done. The mineral fertilization was done in the sow trough Sarruge solution and doses of calcium silicate and sodium, 50, 100, 500 and 1000mg/L-1 and water for the control. The substrate was infested two days after that and a second fertilization was done 10 days after the sow. After 30 days the evaluations took place. The antagonists R14, C16, ENF 24 and T. harzianum inhibited the pathogen with RC from 42 up to 57%. Trichoderma has the hyperparasitic capacity. The incorporation of organic material was not efficient in the control of the disease. The in vivo antagonists reduced the incidence of the disease, but it was effective in the suppression. The oils and plant extracts were not efficient in reduced the incidence. The mineral fertilizations was not able to suppress the disease. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O feijão-caupi, Vigna unguiculata (L.) Walp., é conhecido como feijão-de-corda e feijão-verde sendo uma das principais culturas exploradas pelos pequenos produtores no Nordeste brasileiro. Dentre os fitopatógenos que afetam sua produtividade, destaca-se Sclerotium rolfsii Sacc. que causa a podridão de colo em diversos cultivos do mundo. O objetivo do trabalho foi avaliar o controle alternativo de S. rolfsii Sacc. em mudas de V. unguiculata (L.) Walp. através do uso de antagonistas, incorporação de resíduos orgânicos ao solo, utilização de óleos essenciais, extratos vegetais e ecolife® e nutrição mineral. O trabalho foi desenvolvido no Laboratório de Fitopatologia e em casa de vegetação do CECA/UFAL. O patógeno foi obtido pelo isolamento de folhas de feijão-caupi com sintomas da doença e depois cultivados em arroz esterilizado. Para controle in vitro , os isolados de antagonistas foram pareados com o patógeno em meio de BDA, para avaliar a redução de crescimento micelial (RC) e o hiperparasitismo. Para a biofumigação do solo, as matérias orgânicas cama de frango, marisco, bagaço de cana, resíduo de feijão, raspa de mandioca foram desidratadas em estufa 55ºC por 96h, moídas e incorporadas ao substrato infestado, em concentrações de 10% e 20% (v/v) por 20 dias e comparadas ao tiofanato metílico e a testemunha. Após 30 dias, as plantas foram avaliadas quanto à incidência da doença e desenvolvimento da planta. No controle in vivo as sementes foram microbiolizadas com os antagonistas (C110, C21, ENF24, R14 e Trichoderma harzianum), o fungicida e água salina para testemunha. O substrato foi infestado com o patógeno, dois dias após o semeio foram avaliadas com 30 dias. Para as substâncias naturais, plantas de feijão-caupi, com 21 dias de idade foram pulverizadas com extrato de manipueira (40%), óleo de eucalipto (1%), hortelã pimenta (1%), Ecolife® (2%), tiofanato metílico (0,7 g/L) e água para a testemunha. Após dois dias, o substrato foi infestado com o patógeno. Ao completar seis dias da infestação, uma nova pulverização foi realizada. A adubação mineral foi realizada no semeio através de solução de Sarruge e doses de silicato de cálcio e sódio, 50, 100, 500 e 1000mg/L-1 e água para testemunha. O substrato foi infestado dois dias depois e uma segunda adubação foi feita 10 dias após o semeio. Os antagonistas R14, C16, ENF 24 e T. harzianum inibiram o patógeno com RC de 42 a 57%. Trichoderma teve capacidade hiperparasitária. A incorporação da matéria orgânica não foi eficiente no controle da doença. Os antagonistas in vivo reduziram a incidência da doença e contribuiu para o desenvolvimento das plantas. Os óleos e extratos vegetais não foram eficientes em reduzir a incidência da doença. A adubação mineral não foi capaz de suprimir a doença.

Rhizoctoniasis of potato occurs in all regions of the world where the crop is grown. The disease is caused by various anastomosis groups (AGs) of the fungus Rhizoctonia solani, of which AG-3 is the most common. Very little information is available on the AGs involved in potato rhizoctoniasis in South Africa. This study elucidated the etiology of the disease in the country and also provided guidelines regarding alternative control strategies. The vast majority (99.3 %) of R. solani isolates from symptomatic potato tubers collected at seven of the 14 potato production regions in South Africa belonged to AG-3, and 0.7 % to AG-5. Of the isolates from infected stems and roots, 82.1 % were AG-3, 12.8 % AG-4, and 5.1 % AG-5. Isolations from soil yielded 67.7 % AG-3, 22.0 % AG-4, 5.5 % AG-5, and 2.4 % of each of AG-7 and AG-8. In vitro screening indicated that AG-3 isolates were the most virulent. The progeny of seed tubers naturally infected with R. solani was rendered free of infection by dipping the tubers in hot water at 55 C for 8 minutes, 60 ºC for 6 minutes, or 65 ºC for 4 minutes. However, treatments more severe than 55 ºC for 8 minutes progressively increased tuber mortality. OA5 DP, an organic tin complex, proved to be the most effective of 20 disinfectants for killing sclerotia of the pathogen on seed tubers and rendering the progeny free of infection, but exhibited acute phytotoxicity towards the tubers. Significant control without any phytotoxicity was achieved with the didecyl ammonium chloride compound, Sporekill. Tolclofos-methyl was the only fungicide that provided total control of potato rhizoctoniasis, whereas seed tuber treatment with fludioxonil, kresoxim-methyl and metam-sodium significantly reduced disease in the progeny. Incorporation of of the biocontrol formulation TrykocideTM (Trichoderma harzianum) into soils artificially infested with R. solani AG-3 eradicated the pathogen. Significant reductions in pathogen populations were also evident in soils amended with azoxystrobin, kresoxim-methyl, MaxifloTM Azospirillum brasilense), AvogreenTM (Bacillus subtilis), cattle, chicken and sheep manure, citrus and mango waste compost, composted kraal manure, and shoot tissues of Brassica napus, B. oleracea var. capitata, Raphanus sativus, Sinapsis alba and Tagetes minuta. TrykocideTM provided total control of stem canker in artificially infested soil, whereas kresoxim-methyl, azoxystrobin, sheep manure, B. napus and B. oleracea var. capitata shoot tissue, mango waste compost, and the systemic resistance-inducing compound, acibenzolar-s-methyl, reduced the disease significantly. / Dissertation (MSc (Plant Pathology))--University of Pretoria, 2006. / Microbiology and Plant Pathology / unrestricted

The meals from many oilseed crops contain biocidal chemicals that are known to inhibit the growth and activity of several soil pathogens, though little is known concerning impacts on whole soil microbial communities. We investigated the effect of oilseed meals (SMs) from both brassicaceous plants, including mustard and camelina, as well as non-brassicaceous plants, including jatropha and flax, on P. omnivora (the casual agent of cotton root rot) in Branyon clay soil (at 1 and 5% application rates). We also investigated the effect of SMs from camelina, jatropha, flax, and wheat straw on microbial communities in Weswood loam soil. We also used four types of isothiocyanates (ITCs) including allyl, butyl, phenyl, and benzyl ITC to test their effects on P. omnivora growth on potato dextrose agar (PDA), as well as on soil microbial communities in a microcosm study. Community qPCR assays were used to evaluate relative abundances of soil microbial populations. Soil microbial community composition was determined through tag-pyrosequencing using 454 GS FLX titanium technology, targeting ITS and 16S rRNA gene regions for fungal and bacterial communities, respectively. The results showed that all tested brassicaceous and jatropha SMs were able to inhibit P. omnivora sclerotial germination and hyphal growth, with mustard SM being the most effective. Flax didn't show any inhibitory effects on sclerotial germination. All tested ITCs inhibited P. omnivora OKAlf8 hyphal growth, and the level of inhibition varied with concentration and ITC type. Total soil fungal populations were reduced by ITC addition, and microbial community compositions were changed following SM and ITC application. These changes varied according to the type of SM or ITC added. Our results indicated that SMs of several brassicaceous species as well as jatropha may have potential for reducing cotton root rot as well as some other pathogens. Different SMs releasing varied ITCs may result in differential impacts on soil microorganisms including some pathogens.

Les nématodes à galles demeurent l'un des problèmes les plus graves des ‎agriculteurs de serres du Liban et du Moyen-Orient. Dans le passé, la fumigation du sol au ‎bromure de méthyle a été considérée comme la meilleure mesure de contrôle contre ces ‎nématodes. Toutefois, à la lumière de l'élimination globale du bromure de méthyle, l'accès ‎aux alternatives efficaces et durables est devenu une nécessité essentielle.‎L'objectif de cette étude est d'évaluer l'efficacité des deux engrais verts, le radis ‎huileux (Raphanus sativus oleifera) et à la roquette (Eruca vesicaria sativa) appliquées ‎avec ou sans bâche en plastique, séparément et en combinaison avec Oxamyl, dans la ‎gestion des nématodes à galles en cultures de concombres de serre. En outre, cette étude ‎vise à évaluer la faisabilité financière de la technique de biofumigation avec les deux ‎cultures utilisées et de la rentabilité finale de ces engrais verts en termes de taux coût-profit ‎par rapport au bromure de méthyle.‎A cette fin, trois expériences sur le terrain ont été menées dans des serres ‎commerciales, situées sur la zone côtière du Liban.‎Dans les deux expériences A et B, des résultats cohérents ont été enregistrés en ‎termes de production de rendements significativement plus élevés et de la réduction des ‎populations de nématodes avec les engrais verts‎ utilisés avec ou sans bâche en plastique, ‎par rapport au témoin non traité.‎Quant aux résultats obtenus par les engrais verts‎ par rapport ‎ au bromure de ‎méthyle, dans l'expérience A, le rendement produit par le bromure de méthyle était ‎significativement plus élevé que celui du radis huileux avec bâche en plastique. ‎Cependant, la différence n'était pas significative entre la réduction de la population de ‎nématodes résultant du bromure de méthyle et celle du radis huileux avec bâche en ‎plastique. Les différences du rendement ainsi que la réduction des nématodes étaient ‎significatives entre le bromure de méthyle et le radis huileux sans bâche en plastique.‎Dans l'expérience B, aucune différence significative n'a été observée dans le ‎rendement ni la réduction de la population de nématodes entre aucun des deux engrais ‎verts‎ utilisés avec bâche en plastique et le bromure de méthyle. Ces différences étaient ‎significativement en faveur du bromure de méthyle uniquement lorsque le radis huileux a ‎été utilisé sans bâche en plastique.‎Dans l'expérience C, où Vydate (Oxamyl) a été appliqué à la dose de 1 litre par 1,000 ‎m2 à tous les traitements, il n'y avait pas de différence significative dans le rendement ni la ‎réduction de la population de nématodes entre chacun des deux engrais verts utilisés avec ‎ou sans bâche en plastique et le bromure de méthyle.‎L'analyse coût-profit menée sur tous les traitements appliqués dans les 3 ‎expériences a montré que dans tous les cas, tous les traitements appliqués, qu'ils soient ‎chimiques, non-chimique (avec ou sans bâche en plastique) ou en association ont produit ‎des bénéfices nets supérieurs au bromure de méthyle, même lorsque le rendement produit ‎par le bromure de méthyle était significativement plus élevée.‎L'utilisation du plastique pour couvrir les radis huileux a généralement produit de ‎meilleurs résultats en termes de production de rendements plus élevés, une meilleure ‎réduction des populations de nématodes à galles dans le sol, ainsi conduisant à des ‎augmentations raisonnables des profits nets.‎A la base de ces résultats et à la lumière de l'élimination globale du bromure de ‎méthyle, on peut conclure que l'utilisation du radis huileux et la roquette comme engrais ‎verts avec bâche en plastique peut être considéré comme un outil alternatif pour la gestion ‎des nématodes à galles dans la production de concombres de serre dans les conditions ‎libanaises.‎ / Root-knot nematodes remain one of the most serious problems faced ‎by ‎greenhouse farmers of Lebanon and the Middle East region. In the past, soil fumigation ‎with methyl bromide has been considered as ‎the best control measure against root-knot ‎nematodes. However, in the light of the global phase out of methyl bromide, finding ‎efficient and viable alternatives is an essential necessity.‎The objective of this study is to evaluate the efficacy of the two biofumigation ‎crops ‎Oil Radish (Raphanus sativus oleifera) and Arugula (Eruca vesicaria sativa) applied ‎with ‎and without plastic tarp, separately and in combination with Oxamyl in the ‎management of ‎the root-knot nematodes in greenhouse cucumber crops. Additionally, this ‎study aimed at ‎assessing the financial feasibility of the biofumigation technique with the ‎two cops used ‎and the final profitability of these green manure crops in terms of cost to ‎benefit ratio as ‎compared to methyl bromide.‎For this purpose, three field experiments were carried out in ‎commercial ‎greenhouses situated on the coastal zone of Lebanon.‎In both experiments A & B consistent results were recorded in terms of production ‎of ‎significantly higher yields and reduction of nematode population with the ‎biofumigation ‎crops used whether with or without plastic cover, as compared to untreated ‎fallow.‎As to the results achieved by the biofumigation crops with respect to methyl ‎bromide, ‎in experiment A yield produced by methyl bromide was significantly higher than ‎oil radish ‎with plastic cover. However, no significant difference was found between ‎reduction of ‎nematode population resulting from methyl bromide and oil radish with plastic ‎cover. ‎Difference was significant between methyl bromide and oil radish without plastic ‎cover in ‎both yield and reduction of nematodes.‎In experiment B no significant difference was observed in neither yield nor ‎reduction ‎of nematode population between any of the two biofumigation crops used with ‎plastic ‎cover and methyl bromide. These differences were significantly in favor of methyl ‎bromide ‎only when oil radish was used without plastic cover.‎In experiment C where Vydate (Oxamyl) was incorporated at the rate of 1 liter ‎per ‎‎1,000 m2 to all treatments, there was no significant difference in neither yield nor ‎reduction ‎of nematode population between any of the two biofumigation crops used with or ‎without ‎plastic cover.‎Cost-benefit analysis made on all treatments applied in the 3 experiments ‎showed ‎that in all cases, all treatments applied, whether chemical, non-chemical (with or ‎without ‎plastic cover) or in combination have produced higher net profits than methyl ‎bromide, ‎even when yield produced by methyl bromide was significantly higher.‎Use of plastic for covering oil radish has generally produced ‎better results in terms ‎of ‎production of higher yields, better reduction of soil ‎populations of root-knot nematodes‏‎ ‎and ‎‏leading to ‎‏reasonable increases of net profits.‎Based on these findings and in the light of global phase out of methyl bromide, ‎it ‎can be concluded that the use of oil radish and arugula as biofumigation crops with ‎plastic ‎cover can be considered as ‎an alternative management tool for the root-knot ‎nematode in ‎greenhouse cucumber ‎production under Lebanese conditions.‎