EFICACIA DE MEZCLAS DE CEPAS DEL HONGO Beauveria bassiana EN EL CONTROL DE LA BROCA DEL CAFÉ

esporas/mL. En el campo se emplearon parcelas de 25 arboles con diez repeticiones, distribuidas bajo un diseno completamente aleatorio. Por parcela se selecciono un arbol y de este una rama con 50 frutos, sobre las cuales se realizaron infestaciones artificiales del insecto. Despues de 24h, las ramas infestadas se asperjaron empleando una dosis de 2x107esporas/rama de cada tratamiento. Despues de 30 dias, se evaluo la mortalidad de los insectos mediante la diseccion de los frutos. En el laboratorio la mayor mortalidad se obtuvo con la mezcla de cepas de baja virulencia (100%) y la menor, con la cepa Bb9024 (53,3%). En el cafetal se registro la mayor mortalidad con la mezcla de cepas de baja virulencia (66,6%) y la menor con la cepa Bb9020 (53,1%), entre las cuales hubo diferencias estadisticas, pero no con el resto de los tratamientos. Se concluye que con la mezcla de cepas de baja virulencia se obtienen mayores porcentajes de mortalidad. La mezcla de cepas de alta virulencia se comporto de una manera diferente en el campo, lo cual implica interacciones desconocidas con el medio ambiente. Palabras clave: Patogenicidad, Hypothenemus hampei, diversidad, sinergismo, antagonismo, control biologico, entomopatogenos. ABsTRACT Under laboratory and field conditions coffee berry borer mortality rate caused by seven stocks of the Beauveria bassiana fungus, a mixture of high-virulence stocks and another one of low-virulence stocks was evaluated. In the laboratory, the insect mortality percentage was calculated by infecting coffee berry borers with 1x10 6 spores/ mL. In the field, 25-tree plots with three repetitions distributed through a completely randomized design were used. One tree per plot and a branch with 50 berries were selected to make artificial infestations of the insect. After 24h, the infested branches were sprayed using a dose of 2x107spores/branch for each treatment. After 30 days, the insects mortality was assessed through berries dissection. In the laboratory, the highest mortality was obtained through a mixture of low-virulence stocks (100%) and the lowest with the stock Bb9024 (53.3%). In the coffee plantation, the highest mortality was registered with the low-virulence stocks mixture (66.6%) and the lowest with the stock Bb9020 (53.1%), there were statistic differences between them, but not with the rest of the treatments. It is concluded that with the mixture of low-virulence stocks high mortality percentages are obtained. The high-virulence stocks mixture behaved in a different way in the field, which implies unknown interactions with the environment