Entomopathogenic fungi as potential control agents against the Brazilian ground pearl Eurhizococcus brasiliensis (Hemiptera: Margarodidae) Hongos entomopatógenos como agentes potenciales de control contra la perla de tierra, Eurhizococcus brasiliensis (Hemiptera: Margarodidae)

The Brazilian ground pearl Eurhizococcus brasiliensis is the most prevalent insect pest of grapes in Brazil. The natural occurrence and biological activity of entomopathogenic fungi (EF) against this pest are poorly known. In this study, we evaluate the presence of E. brasiliensis-associated EF in soil and the virulence of a ground pearl-derived strain of Isaria fumosorosea against cysts under laboratory conditions. EF were not identified on cysts in an initial survey performed in a grape-producing area in southern Brazil. However, 6% of mobile females that had emerged from cysts were infected by Metarhizium brunneum, which was the first report of this insect pathogen on ground pearls in Brazil. Cysts without the protective wax layer were inoculated with I. fumosorosea conidia suspension by immersion. The symptoms and the signs of the disease were described. Infected cysts had a yellow-ochre color and "hard-boiled egg" consistency when broken, in contrast to the intense bright yellow color and "raw egg" consistency of living cysts. Vegetative fungal cells were present inside symptomatic cysts, and later, outside conidiation was visible. The LC25 for the cysts protected with the wax layer and also inoculated by immersion was 1.31 x 10(7) conidia·mL-1. However, the presence of fungal structures was not observed on symptomatic individuals. Considering the motionlessness of cysts and the absence of disease signs for mortality assessment, the symptoms described may be helpful for further studies on E. brasiliensis control using I. fumosorosea. La perla de tierra Eurhizococcus brasiliensis es el insecto plaga más importante en las uvas de Brasil. La presencia natural y actividad biológica de hongos entomopatógenos (HE) contra esta plaga son poco conocidas. En este estudio se evaluó la presencia de E. brasiliensis asociada a HE en suelos y la virulencia de una cepa de Isaria fumosorosea proveniente de la perla de la tierra contra quistes bajo condiciones de laboratorio. No se logró identificar ningún HE en los quistes durante una evaluación inicial conducida en un área de producción de uva al sur de Brasil. Sin embargo, el 6% de las hembras móviles que emergieron de los quistes estaban infectadas con Metarhizium brunneum, el cual es el primer reporte del aislamiento de este patógeno sobre perlas de la tierra en Brasil. Los quistes sin su capa de cera protectora fueron inoculados por inmersión a una suspensión de conidios de I. fumosorosea. Se describieron los síntomas y signos de la infección. Los quistes infectados tenían un color amarillo oscuro y una consis