Virginia ranks third in fresh market staked tomato (Lycopersicon esculentum Mill.) production with approximately 1,659 hectares on the Eastern Shore. Estimated annual gross value is $30,800,000. Copper and chlorothalonil have long been considered essential to control bacterial and fungal diseases in fresh market tomatoes. High rates of these fungicides on tomatoes grown under plastic mulch have led to concerns about their potential adverse effect on water quality in estuaries adjacent to fields. The development of new fungicides, such as azoxystrobin and acibenzolar-S-methyl, which have more favorable environmental fate characteristics and are used at much lower rates, may provide viable alternatives to copper and chlorothalonil. Using a disease forecasting system, such as Tomcast, may reduce the number of applications of fungicides. The research objectives of this study were to reduce the amount of copper and chlorothalonil used in fresh market tomato production and to evaluate the effectiveness of the Tomcast disease forecasting system for controlling fungal leaf diseases on the Eastern Shore. Field studies compared copper to acibenzolar-S- methyl for bacterial diseases caused by Xanthomonas campestris pv. vesicatoria and Pseudomonas syringae pv. tomato. Research plots were established in a randomized complete block design with four replications in grower fields and at the Eastern Shore Agricultural Research & Extension Center. Acibenzolar proved to be as effective as the standard copper bactericides in controlling bacterial spot. Acibenzolar provided better control than the standard copper bactericides when bacterial speck was the target disease. Azoxystrobin application alternated with maneb was evaluated as a replacement for chlorothalonil. Azoxystrobin and Tomcast were studied as tools to reduce chlorothalonil use for control of Alternaria solani. Tomcast can reduce the number of applications by 40-70 % per year and provide adequate control of early blight. Azoxystrobin provides better control of early blight than chlorothalonil. Use of these new, more environmentally compatible, plant-protection products , along with the Tomcast disease forecasting system, can significantly reduce or eliminate the need to use copper and chlorothalonil for tomato disease management and therefore eliminate them as potential pollutants of the Chesapeake Bay and Atlantic Ocean estuaries. / Master of Science

Submitted by ERIKA OLIVEIRA DA SILVA (erikaagro@gmail.com) on 2018-08-24T14:30:24Z No. of bitstreams: 1 Tese Érika Final Conferida com ficha (1).pdf: 975581 bytes, checksum: c0158160c152b2695ba62e395d73b676 (MD5) / Approved for entry into archive by Maria Lucia Martins Frederico null (mlucia@fca.unesp.br) on 2018-08-24T15:28:34Z (GMT) No. of bitstreams: 1 silva_eo_dr_botfca.pdf: 975581 bytes, checksum: c0158160c152b2695ba62e395d73b676 (MD5) / Made available in DSpace on 2018-08-24T15:28:34Z (GMT). No. of bitstreams: 1 silva_eo_dr_botfca.pdf: 975581 bytes, checksum: c0158160c152b2695ba62e395d73b676 (MD5) Previous issue date: 2018-06-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A pinta bacteriana do tomateiro, causada por Pseudomonas syringae pv. tomato Okabe (Pst), é uma das principais doenças da cultura, pois pode reduzir a qualidade e o rendimento da produção, afetando o mercado de tomates frescos e transformados. A semente de tomate infectada por Pst, além de manter a bactéria viável por um longo período, também é importante por ser uma fonte primária de inóculo, justificando a necessidade de utilização de sementes isentas do patógeno. Desse modo, esse trabalho teve como objetivos avaliar a eficiência da termoterapia e da aplicação de óleos essenciais como alternativas para o tratamento de sementes de tomate, visando ao manejo de Pst. Inicialmente, foi verificada a ação in vitro dos óleos essenciais (OE) de citronela (Cymbopogon nardus (L.) Rendle), capim-limão (Cymbopogon citratus (DC.) Stapf), tomilho (Thymus vulgaris L.) e melaleuca (Melaleuca alternifolia Cheel), nas concentrações de 1%, 2% e 3%, utilizando-se leite em pó (LP - 1%) como emulsificante. Sulfato de estreptomicina (25mg/mL) e água esterilizada + LP foram incluídos como testemunhas. Os OE de tomilho (2 e 3%) e de citronela (nas três concentrações) e o sulfato de estreptomicina inibiram o desenvolvimento da colônia bacteriana, promovendo a formação do halo de inibição. Em seguida, foram conduzidos experimentos independentes, um para testar o tratamento de sementes com os OE selecionados (citronela a 1% e tomilho a 2%) e outro, com a termoterapia (50°C/30’ e 50°C/25’). Todos os experimentos foram realizados em duplicata. Foram avaliados a incidência de Pst nas sementes, a germinação e o vigor (altura de plantas). Todos os tratamentos testados promoveram a erradicação de Pst nas sementes. A presença de Pst nas sementes não interferiu na germinação destas, mas promoveu uma redução na altura das plantas. O tratamento com OE de tomilho resultou em redução significativa da germinação e do vigor. Os tratamentos térmico (ambas as combinações temperatura/tempo de exposição) e com óleo essencial de citronela a 1% mostraram-se alternativas viáveis para o manejo de Pst em sementes de tomate. / The bacterial speck of tomato, caused by the bacterium Pseudomonas syringae pv. tomato (Pst), is among the main diseases of this crop, as it can reduce the quality and production yield, affecting the market of fresh and processed tomatoes. Pstinfected tomato seed, besides maintaining the bacterium viable for a long period, is also important because it is a primary source of inoculum, demonstrating the need of using Pst-free seeds. Thus, the objective of this work was to evaluate the efficiency of thermotherapy and the application of essential oils as alternatives for tomato seeds treatment, aiming at the management of Pst. Initially, the essential oils (EO) of citronella, lemon grass, thyme and tea tree were evaluated in concentrations of 1%, 2% and 3% (powder milk (PM - 1%) was used as emulsifier). Streptomycin sulfate (25mg/mL) and sterile water + PM were included as controls. Thyme (2% and 3%) and citronella (at three concentrations) EO and streptomycin sulfate inhibited the bacterial colonies development, promoting inhibition halo the formation. Then, independent experiments were carried out, one to test the seed treatment with the selected EOs (citronella 1% and thyme 2%) and another with thermotherapy (50°C/30' and 50°C/25'). All experiments were performed in duplicate. The incidence of Pst in seeds, germination and vigor (plant height) were evaluated. All the tested treatments promoted the eradication of Pst in the seeds. Pst presence in the seeds did not interfere in seeds germination, but promoted a reduction in plant height. Treatment with thyme EO resulted in a significant germination and vigor reduction. Thermal treatments (both temperature/exposure time combinations) and 1% citronella EO were found to be viable alternatives for Pst management in tomato seeds.