Resumen: En Uruguay, la superficie cultivada con olivo (Olea europaea) se ha expandido en los últimos años, alcanzando las 10.000 hectáreas aproximadamente. Entre las enfermedades foliares favorecidas por las condiciones climáticas de temperaturas moderadas, humedad relativa alta y precipitaciones abundantes, se destaca la ´mancha ojo de pavo´ o ´repilo´ causada por el hongo Venturia oleaginea. En 2015 y 2016, con la finalidad de conocer el comportamiento de cultivares introducidos al país frente a este hongo se realizaron ensayos a campo, invernáculo y laboratorio. Se determinó la incidencia y la severidad de acuerdo a una escala elaborada en base al área foliar afectada y/o el número de lesiones por hoja tanto en lesiones visibles como latentes visualizadas mediante tratamiento con NaOH. Los resultados a campo con infecciones naturales y de los ensayos bajo condiciones controladas indicaron que ´Frantoio´, ´Leccino´ y ´Picual´ fueron los cultivares de mejor comportamiento frente a V. oleaginea.´Arbequina´ mostró un comportamiento intermedio, mientras que ´Barnea´,´Coratina´ y ‘Manzanilla’ fueron los más susceptibles.

Summary: In Uruguay, the area cultivated with olive (Olea europaea) has increased in recent years reaching approximately 10,000 hectares. Among the foliar diseases favored by mild temperatures, high relative humidity, and abundant rainfall, olive scab or peacock spot caused by the fungus Venturia oleaginea is the most important. In 2015 and 2016, with the objective of knowing the response of olive cultivars introduced in Uruguay against this fungus, field, greenhouse, and laboratory trials were carried out. Disease incidence and severity were recorded based on a scale of the affected leaf area and/or the number of lesions per leaf, considering both visible and latent lesions after NaOH treatment. Results from field data, greenhouse and laboratory trials indicated that ´Frantoio´, ´Leccino´ and ´Picual´ were the cultivars with the best behavior against V. oleaginea. ´Arbequina´ had intermediate values while ´Barnea´, ´Coratina´ and ´Manzanilla´ were the most susceptible.

En los sistemas de producción agropecuaria se recomienda la incorporación de materia orgánica para minimizar la degradación del recurso suelo. Los desechos orgánicos provenientes de plantas de tratamiento de líquidos residuales domésticos (PTARD), denominados lodos urbanos, constituyen una fuente de materia orgánica con potencial uso agrícola. El presente trabajo planteó evaluar el uso de lodos urbanos como enmienda orgánica en cultivos y determinar la posible contaminación de cultivos y suelo con patógenos humanos presentes en los lodos. Durante seis ciclos con lechuga, se comparó la productividad y nivel de nitratos en hoja luego del agregado de lodos urbanos frescos y compostados, cama de pollo y fertilización química (en base a igual aporte de N). Solo en un ciclo los rendimientos fueron menores que la fertilización química y los niveles de nitratos en hojas nunca superaron los máximos permitidos. No se observó contaminación por patógenos ni en los vegetales cultivados ni en el suelo con los lodos empleados. A su vez en 13 partidas de lodos frescos analizadas el nivel de coliformes fecales fue altamente variable, en siete se detectaron bacterias del género Salmonella, y en una huevos de helmintos. Los resultados indican la potencialidad de los lodos urbanos compostados como enmienda orgánica. Sin embargo la seguridad de su empleo en la producción de alimentos dependerá de la carga de patógenos humanos y de factores no analizados en el presente trabajo como carga de metales pesados y tiempo de espera luego de su aplicación.

In agricultural systems, soil amendments with organic matter are advised in order to minimize soil degradation. The organic matter originated at the household wastewater treatment facilities (PTARD) called sewage sludge originated at household wastewater treatment facilities (PTARD), called urban sludge, is a potential source of organic matter for agricultural use. In this work we aimed to evaluate the agronomic potential of domestic sewage sludge to be used as soil organic amendment in crop production and to evaluate the risk of crop and soil contamination with human pathogens. Along six lettuce crop cycles we compared the productivity and leaf tissue nitrate content where fresh and composted sewage sludge, chicken bed and chemical fertilizers were applied, all with an equal supply of N. In only one cropping cycle lettuce yields were lower than with chemical fertilization, and leaf tissue nitrates were always within the maximum thresholds allowed. No contamination of soil and lettuce leaves with human pathogens was detected. Among the 13 sewage sludge samples analyzed, fecal coliforms levels were highly variable, bacteria belonging to Salmonella genus were detected in seven samples and helminthes eggs were found in only one sample. The results indicate the potential of composted urban sludge as organic amendment. Nevertheless, the safe use of sewage sludge in food production will also depend on its levels of human pathogens and on other factors not analyzed in the present work, like the level of heavy metals and the time interval between application and crop harvest

Uma alternativa de manejo das doenças causadas por Phytophthora spp. é o uso de matéria orgânica. No presente trabalho foi avaliada a potencialidade do lodo de esgoto na indução de supressividade in vitro a P. nicotianae. O efeito do lodo de esgoto incorporado ao solo na sobrevivência de P. nicotianae foi avaliado mediante um experimento fatorial com dois fatores: doses de lodo de esgoto (0, 10, 20 e 40% p/p) e concentrações de inóculo [0, 10 ou 20 g de grãos de trigo (Triticum aestivum) colonizados kg-1]. Aos 21 dias, quando aumentaram as doses de lodo de esgoto, a sobrevivência de P. nicotianae e os pHs das misturas diminuíram, e as condutividades elétricas (CE) aumentaram. As correlações entre a CE e a sobrevivência do patógeno foram negativas e significativas (P>0,05). Para estudar o efeito dos compostos químicos envolvidos na supressividade, foram obtidos extratos em água, H2SO4 2N e KOH 0,4N de misturas de areia – lodo de esgoto (20% p/p), e foram acrescentados ao meio de cultura e seu efeito avaliado no crescimento das colônias de P. nicotianae. O extrato ácido (H2SO4 2N) do tratamento com 20% de lodo de esgoto inibiu significativamente (P>0,05) o crescimento da colônia do patógeno. O efeito biológico foi estudado mediante isolamento de microrganismos em meio de cultura e seleção por antagonismo. No bioensaio com plântulas de alfafa (Medicago sativa) destacaram-se os isolados F9.1 (Aspergillus sp.) e A12.1 (actinomiceto, não identificado); e no teste de culturas pareadas destacou-se um Trichoderma sp. e dois actinomicetos por antibiose, e um Trichoderma sp. e três Aspergillus sp. por hiperparasitismo.

Soil organic matter amendments may provide an alternative management practice for soil diseases caused by Phytophthora spp. In this paper we have evaluated the effectiveness of residential sewage sludge to suppress P. nicotianae under laboratory conditions. The effect of sewage sludge on P. nicotianae survival was evaluated by two experimental factors: sewage sludge doses (0, 10, 20 and 40% w/w) and inoculum level [0, 10 and 20 g infested wheat (Triticum aestivum) seeds per kg of soil]. After maintaining the mixtures (soil – sewage sludge – inoculum) at room temperature for 21 days, treatments with higher organic matter had lower P. nicotianae survival, pH of the mixture, and higher electric conductivity (EC). Correlations between pathogen survival and EC were negative and significant (P>0,05). In order to evaluate the chemical effects of the sewage sludge on P. nicotianae, water, H2SO4 2N e KOH 0,4N extracts were obtained from sand - sewage sludge (20% w/w) mixtures and each one of them was added to culture medium. The H2SO4 2N extract significantly (P>0,05) inhibited colony growth. The biological effect of the sewage sludge was evaluated by isolating microbial antagonists and testing them against P. nicotianae by bioassay and plate techniques. The bioassay technique selected one fungus (isolate F9.1, identified as Aspergillus sp.) and one actinomycete (isolate A12.1, not identified). The plate technique selected one Trichoderma sp. and two actinomycetes for their antibiosis to P. nicotianae, and one Trichoderma sp. and three Aspergillus sp. for their hyper-parasitism to the pathogen.