Susceptibilidad de los instares de Spodoptera frugiperda al hongo Nomuraea rileyi
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Instituto Colombiano Agropecuario
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El objetivo de esta investigación fue determinar la susceptibilidad de los diferentes instares de Spodoptera frugiperda (J.E. Smith) al hongo Nomuraea rileyi (Farlow) Samson. Se usó la cepa NRBI, mantenida en el laboratorio de Entomología del ICA en "Tulio Ospina", empleando una concentración de 0.87 conidias/mm², la cual corresponde a la dosis letal media obtenida en un estudio previo. La edad promedia de las conidias fue de 20 días y el número de instares que desarrollaron las larvas de S. frugiperda durante el estudio fue de cinco, alimentadas con follaje de maíz proveniente de plantas de 61-90 días de edad. El follaje de maíz se asperjó con el inóculo y las larvas de los diversos instares se alimentaron del follaje tratado durante 24 horas; posteriormente se individualizaron y se les suministró alimento fresco de maíz previamente desinfectado. El experimento se planeó en un diseño completamente al azar con tres repeticiones de 30 larvas cada una. Los promedios de mortalidad causados por N. rileyi en los diversos instares de S. frugiperda fueron: 83.33% para el primer instar, 95.50% para el segundo, 48.83% para el tercero, 62.16% para el cuarto y 3.33% para el quinto. Se encontró diferencias significativas (P= a 0.05) entre la mortalidad del primero y segundo instar. El tiempo letal medio (TL sub 50) fue de 10.20 y 15.46 días para los instares cuarto y primero, respectivamente. En conclusión, el segundo instar fue el más susceptible al N. rileyi.
The objective of this research was to determine the susceptibilty of the different instars of Spodoptera frugiperda (J.E. Smith) to the fungus Nomuraea rileyi (Farlow) Samson. The strain NRBI of N. rileyi was used at a concentration of 0.87 conidia/mm², wich is the median lethal dosage obtained in a previous study. The average age of the used conidia was 20 days, and the instar number of S. frugiperda was five when fed on corn foliage from plants 61-90 days old. The corn foliage was sprayed with the fungus and larvae were left one per cage, and fresh untreated foliage was provided. The experimental design consisted of a complete randomized one with three replications and 30 larvae per instar. Average mortality caused by N. rileyi in each of S. frugiperda instars was as follows; 83.33% for the first instar, 95.5% for the second, 48.83% for the third, 62.16% for the fourth and 3.33% for the firth. There were significant differences (P = 0.05) in mortality between the first and second instar. The TI 50 was 10.2 and 15.46 days for the fourth and first instar, respectively. In conclusion, the second instar was the most susceptible one to N. rileyi.
Maíz
Zea mays
The objective of this research was to determine the susceptibilty of the different instars of Spodoptera frugiperda (J.E. Smith) to the fungus Nomuraea rileyi (Farlow) Samson. The strain NRBI of N. rileyi was used at a concentration of 0.87 conidia/mm², wich is the median lethal dosage obtained in a previous study. The average age of the used conidia was 20 days, and the instar number of S. frugiperda was five when fed on corn foliage from plants 61-90 days old. The corn foliage was sprayed with the fungus and larvae were left one per cage, and fresh untreated foliage was provided. The experimental design consisted of a complete randomized one with three replications and 30 larvae per instar. Average mortality caused by N. rileyi in each of S. frugiperda instars was as follows; 83.33% for the first instar, 95.5% for the second, 48.83% for the third, 62.16% for the fourth and 3.33% for the firth. There were significant differences (P = 0.05) in mortality between the first and second instar. The TI 50 was 10.2 and 15.46 days for the fourth and first instar, respectively. In conclusion, the second instar was the most susceptible one to N. rileyi.
Maíz
Zea mays
Palabras clave
Enfermedades de las plantas - H20, Spodoptera frugiperda, Control biológico, Nomuraea, Desarrollo biológico, Maíz, Enfermedades de las plantas, Transitorios