Isolates of the late blight pathogen Phytophthora infestans (n = 327) from the central to southern Peruvian Andes were systematically collected in 1997 to 1999 and analyzed to determine the pathogen's population structure at its host's center of diversity. No isolates of the A2 mating type were detected. Cluster analysis of DNA fingerprinting data indicated that the collection consisted of five major groups that were interpreted to be clonal lineages. Two of the lineages (US-1 and EC-1) have been previously described, and three (PE-3, 5, and 6) are described here for the first time. Collections from three areas in the central Peruvian Andes, including two key sites used in an international potato breeding program, consisted of isolates of the EC-1 lineage, which has been reported to dominate the pathogen population in Andean countries to the north of Peru. The collections from Cusco and Puno were more diverse. More than one lineage was detected in 10 of the 20 fields sampled in Cusco. Data on virulence, metalaxyl sensitivity, and band data for allozymes, mitochondrial DNA, and ipiB1 suggested that PE-3 may have been produced through recombination events between US-1 and EC-1. Restriction fragment length polymorphism and amplified fragment length polymorphism marker data were not consistent with this hypothesis.

Soil fertilization with organic fertilizers comprises a practice that improves the soil biological properties; however, the effect of these on the soil food web (SFW) has been scarcely studied. The aim of this study was to determine the effect of two commercial organic fertilizers on the structure of the SFW associated with roots of blackberry plants (Rubus adenotrichos). The research was conducted in two blackberry plantations located one in San Martín de León Cortés, and the other one in Buena Vista de Pérez Zeledón in San José, Costa Rica, from August to December, 2010. In the two plantations, plants were fertilized with compost or vermicompost. The roots of blackberry plants surrounding soil were sampled in order to quantify groups of the SFW through the following techniques: bacteria and filamentous fungi by plate count, protozoa by the most probable number, spores from arbuscular mycorrhizal fungi and nematodes by flotation-centrifugation, microarthropods, macroarthropods, and worms were directly counted in soil samples. The dataset was analyzed by multidimensional scaling analysis. The addition of organic fertilizers to soil caused a differential effect on the structure of the SFW (as compared with non-fertilized soils). The effect differed in soil from each of the experimental plantations according to fertilizer type. The groups of organisms mainly affected were actinomycetes and protozoa, which implies that the structure of SFW and consequently, the function of soil were not affected by the addition of organic fertilizers.

Recibido el 30 de abril de 2013 y aprobado el 5 de julio de 2013 RESUMEN Localización. La Región del Bajo Caguán se encuentra localizada en las riberas del río Cagúan, jurisdicción del municipio de Cartagena del Chaira, suroriente del Departamento del Caquetá en la región Amazónica Colombiana. Objetivo. Compartir los resultados metodológicos y de formación logrados mediante las Escuelas de Campo de Agricultores de Theobroma cacao L. desarrollados por la Universidad de la Amazonia en el marco del proyecto: "Desempeño agronómico, evaluación fitosanitaria y caracterización molecular de clones promisorios de Theobroma cacao L. provenientes de materiales vegetales élite presentes en sistemas productivos del bajo Caguán, municipio de Cartagena del Chairá" (ECAs-CAGUAN) que contó con el apoyo de Colciencias, el Comité de Cacaoteros del Bajo Caguán y Suncillas " Chocaguán" y la Parroquia San Isidro Labrador. Metodología. El trabajo se realizó a partir del aprendizaje por descubrimiento, partiendo de los conocimientos y la experiencia previa de los campesinos, la reflexión, la nueva información y la aplicación de la misma. Esta situación implicó la formación a profesionales como facilitadores de ECAs, la definición participativa del currículo, la construcción de protocolos y la aplicación flexible de estos en campo. Resultados. La ECAs-CAGUAN, en su primer ciclo de formación lograron formar a 43 cultivadores y productores de Theobroma cacao L, es decir que el 78% de los que iniciaron el proceso y se logró un Indice de Incremento del Conocimiento (IIC) del 34%. Una de las lecciones aprendidas y quizás la más importante es la necesidad que las ECAs incorporen otros elementos de trabajo que van más allá de lo técnico y está relacionado con estrategias de trabajo social, afectivo y de sensibilidad, esto contribuirá a mejorar los procesos de adopción tecnológica en campo. Conclusiones. El proceso de las ECAs-Caguan, permitió a los agricultores entre otras cosas entender que el hallazgo de los élites y/o el mejoramiento genético es solo un factor que ayudará a que su producto mejore, pero la mayor responsabilidad está precisamente en ellos mismos, en la realización de las prácticas culturales y de manejo de sus cultivos.

Ethanol (EtOH) 70% is commonly used in collections to preserve and store many unprepared soft-bodied Chalcidoidea. Specimens air-dried directly from alcohol, however, often suffer from collapse of some body parts, making subsequent observation of their morphology difficult or even impossible. We propose an inexpensive method for processing and dry-mounting specimens of Chalcidoidea, using a chemical process including amyl acetate. Four treatments using amyl acetate at different concentrations and exposure times were evaluated for specimens of Eulophidae, Mymaridae, Encyrtidae, Aphelinidae, Pteromalidae, and Trichogrammatidae. Treatment with amyl acetate resulted in specimens of consistently higher quality. Based on our results, treatment of specimens for 1 h with 50:50 amyl acetate and ethanol mixture, followed by treatment for 1 h with 100% amyl acetate, yielded specimens adequate for morphological observations for most of the families. Further experiments are required, however, to optimize this approach for Trichogrammatidae and Eulophidae. This method is a relatively simple, inexpensive, and safe alternative to other methods commonly used for restoring Chalcidoidea preserved in alcohol.

Steneotarsonemus spinki constituye una de las plagas de reciente aparición y de las más notables para el arroz en Costa Rica. El objetivo de este trabajo fue determinar en campo las arvenses, asociadas a campos de arroz en Costa Rica, que sirven de hábitat al ácaro S. spinki. Entre agosto y septiembre, 2007, se tomaron muestras de plantas asociadas a 16 campos de arroz Oryza sativa, en cuatro zonas arroceras: Brunca, Pacífico Central, Huetar Atlántico y Chorotega; afectadas por altas densidades poblacionales del ácaro S. spinki. Con la ayuda de estereoscopio se determinó la presencia de S. spinki en las especies arvenses Echinochloa colona, Eleusine indica, Oryza latifolia y Rottboellia cochinchinensis; y densidades poblacionales de 0,4; 0,1; 13,2 y 0,2 ácaros/ planta, respectivamente.Palabras clave: Oryza sativa, Steneotarsonemus spinki, plantas hospedantes.