The fall armyworm (Spodoptera frugiperda (J.E. Smith)) is an important harmful pest for corn crops in Colombia. Knowing its population’s fluctuation regarding genetically modified plants allows the implementation of monitoring plans and time-effective management actions. The objective of this study was to establish the population’s fluctuation of S. frugiperda during 2014-2016 in the hybrids 30F35R and 30F35HR (genetically modified with the Cry1F endotoxin) in El Espinal, Tolima, Colombia. Accumulations in five growing cycles were carried out until 20, 40, 60, 80, and 104 days with the number of larvae per linear meter after emergence per year and per hybrid. Results were compared statistically using linear mixed models. On the other hand, two dummy variables that reckon the presence of larvae and damage were calculated. With the indicators of presence (one) and absence (zero), a longitudinal logistic prediction model was constructed. Larger accumulation of larvae was registered in the hybrid 30F35R (6.79±0.20); however, the genetically modified genotype 30F35HR also registered the presence of larvae (4.24±0.20), inferring that the endotoxin did not exercise total control over the populations. The vegetative stage showed a higher larval population. However, when this stage is not managed, the crop can show damage up to 52% and 72% in hybrid plants with and without Cry1F, respectively. This behavior suggests that if refuge areas and strategies such as pest monitoring are not established, these insects could generate higher resistances to the plants with the endotoxin Cry1F.

No abstract

Spodoptera frugiperda (J.E. Smith) is the pest insect that produces the highest losses in maize production in the tropics and neotropics. Its control in Colombia comprises about 10% of the total production costs. The aim of this study was to determine the economic injury level (EIL) and define action thresholds (ATs) for this insect pest in the maize hybrids 30F35R and 30F35HR (with Cry1F protein) in Espinal, Colombia. In two sowing cycles, a completely randomized design was established for each maize hybrid to measure their yield response at four insect population levels (a control without any applications of insecticides and applications at 2, 5, and 10 larvae per 10 plants). For 30F35R, an inverse relationship was found between levels of infestation and yields; meanwhile, for 30F35HR, only during the first cycle this relationship was found. The EIL calculated for 30F35R showed an average of 2.6 and 1.9 larvae per 10 plants in the first and second cycles, respectively, and 2.8 for 30F35HR in the first cycle. Two ATs were established, one in the period from 0 to 20 days after emergence (DAE) and another from 20 to 40 DAE. The threshold for 30F35R from 0 to 20 DAE showed an average of 1.8 larvae per 10 plants in both cycles, while, from 20 to 40 DAE, it was 2.0 and 1.7 in the first and second cycles, respectively. In 30F35HR, the thresholds were 2.1 and 2.5 larvae per 10 plants on average for both periods of the first cycle, respectively. These results can be considered as a tool within integrated pest management that also includes biological and cultural control strategies.

No abstract

La arracacha se ha convertido en parte importante de la alimentación en la zona andina de Suramérica con gran arraigo cultural. Sin embargo, la única variedad regional cultivada en más del 90 % del país se denomina amarilla común, un material sembrado durante más de 30 años que ha disminuido su potencial productivo dejando a los productores sin otras alternativas. El 94.6 % de las accesiones de arracacha conservadas por el Sistema de Bancos de Germoplasma de la Nación para la Alimentación y la Agricultura (SBGNAA) de Colombia corresponden a colectas nacionales. La identificación y la evaluación del recurso genético permiten identificar los rasgos de selección deseados para futuros proyectos de mejoramiento. 96 accesiones fueron caracterizadas durante el 2016, se observó amplia variabilidad en 11 caracteres cuantitativos y 30 cualitativos. Mediante análisis factorial para datos mixtos (AFDM) y análisis de clúster, se determinaron seis grupos completamente diferenciados según el porte de la planta, el cual estuvo influenciado por las variables altura y diámetro de la planta, longitud del pecíolo, longitud y ancho de la hoja. Las variables cualitativas más importantes correspondieron a color de pulpa de la raíz reservante, pigmentación secundaria de hojas, color secundario del pecíolo y capacidad de florecimiento, convirtiendo estos atributos en factores de selección. El color de la pulpa de la raíz reservante se convirtió en un carácter de selección debido a que en muchas comunidades de la zona andina los materiales son fácilmente distinguibles por el color de la pulpa del nabo.