Abstracto
- The fall armyworm, Spodoptera frugiperda, is the major insect pest of the maize crop. Considering that the country does not nave a registered product based on fungal entomopathogens for the control of S. frugiperda, and given that Nomuraea rileyi is a microorganism that is most frequently found to cause epizootics in the field, our objective was to isolate and select strains of this fungus with high biocontrol activity against S. frugiperda. To do this, the biocontrol activity of 10 isolates of N. rileyi, isolated under laboratory conditions from the Llanos Orientales, at 1×10 7 conidia.ml -1 was evaluated by spraying onto "higuerilla" leaves (Kicinus communis) infested with second instar larvaef A mortality of 94,7, 95 and 100% were obtained with three isolates, the isolate Nm-07 from Villavicencio being selected because it caused 100% mortality and the lowest lethal times (LT 50 and LT 90) of 6, 2 and 7,9 days, respectively. Afterwards, both the lethal concentrations and doses of this isolate were determined, with LC 50, of 9,8 x 10 3 conidia.ml-1 at 11 days and LC90 of 2,2 x10 5 conidia.ml -1 at eight days, respectively. To determine the lethal doses 5 ul of N. rileyi suspensions were applied to the thoracic tergum of each larvae, with a LD 50 of 44 conidia/larvae after 12 days and a LD 90 of 3,380 conidia/larvae after 10 days, respectively. These results offer reference parameters to conduct studies on mass production and formulation directed towards the integrated control of Spodoptera spp. © 2011 Sociedad Colombiana de Entomología.
