Distribución temporal y espacial de poblaciones larvarias de Spodoptera frugiperda (Smith) (Lep.: Noctuidae) en diferentes hospederos en provincias del norte de la Argentina

in order to study the spatial and temporal distribution of fall armyworm spodoptera frugiperda larval populations on different host plants, systematic samplings were made from 2004 to 2007 in different crop associations in the provinces of tucumán, salta and santiago del estero. a zone where more than two adjacent crops coexisted simultaneously (in time and space) was considered a crop association. sampled crops were corn, sorghum, alfalfa, sugarcane, soybean, wheat, safflower, chickpea and weeds. five one-square-meter spots were randomly selected in each plantation and plants were checked for egg masses and/or larvae, which were collected. 3620 larvae were found, most of them being collected in all provinces during summer months in the three evaluated crop seasons. larval presence was related to summer crops (corn and sorghum) in all provinces. the highest larval number was obtained in corn (2894), independently of the other crops in the association. the other important crops infected with larvae were: sorghum (272), alfalfa (125), and weeds (282). considering the number of larvae collected, soybean, wheat, and sugar cane, crops that were present in almost all the associations, are not preferential hosts for this species.