Natural Distribution of Parasitoids of Larvae of the Fall Armyworm, Spodoptera frugiperda, in Argentina

To develop a better understanding of the natural distribution of the fall armyworm, Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae), and to update the knowledge of the incidence of its complex of parasitoids. S. frugiperda, samplings in whorl-stage corn were carried out in provinces of Argentina from 1999 to 2003. S. frugiperda larvae were collected from corn in localities of the provinces of Tucumán, Salta, Jujuy, Santiago del Estero, La Rioja, Córdoba, San Luis, Chaco and Misiones. In each locality 30 corn plants were sampled and only larvae located in those plants were collected. The parasitoids that emerged from S. frugiperda larvae were identified and counted. The abundance of the parasitoids and the parasitism rate were estimated. The S. frugiperda parasitoids collected were Campoletis grioti (Blanchard) (Hymenoptera: Ichneumonidae), Chelonus insularis (Cresson) (Hymenoptera: Braconidae), Archytas marmoratus (Townsend) (Diptera Tachinidae) and/or A. incertus (Macquart), Ophion sp. (Hymenoptera: Ichneumonidae), Euplectrus platyhypenae Howard (Hymenoptera: Eulophidae), and Incamyia chilensis (Aldrich) (Diptera Tachinidae). C. grioti was the most abundant and frequent during the five-year survey. Similar diversity of parasitoids was obtained in all the provinces, with the exception of I. chilensis and E. platyhypenae that were recovered only in the province of Salta. In the Northwestern region, in Tucumán, C. grioti and species of Archytas were the most abundant and frequent parasitoids. On the contrary, in Salta and Jujuy Ch. insularis was the parasitoid most abundant and frequently recovered. The parasitism rate obtained in Tucumán, Salta and Jujuy provinces were 21.96%, 17.87% and 6.63% respectively with an average of 18.93%. These results demonstrate that hymenopteran and dipteran parasitoids of S. frugiperda occurred differentially throughout the Argentinian provinces and played an important role on the natural control of the S. frugiperda larval population

Evaluation of a physiologically based model to predict Dalbulus maidis occurrence in maize crops: validation in two different subtropical areas of South America

The maize leafhopper, Dalbulus maidis (DeLong) (Hemiptera: Cicadellidae), is a specialist herbivore that develops on maize plants (Zea mays L., Poaceae). Every year, it is responsible for considerable reductions in yields of the maize fields of the Americas, because alongside its direct damages it is also a vector of three relevant plant pathogens. The transmitted diseases come to have a high incidence, resulting in significant yield losses, thereby forcing farmers and technicians to attempt a tight control of the fields mostly using non-specific insecticides. Decision support systems based on mathematical models may be valuable in helping to reduce the use of agrochemicals in this regard, as they can provide a projection of the future situation based on past and present data. With this precondition, this work aims to apply and validate a physiologically based model to describe populations of D. maidis developing in two experimental fields located in Argentina, which are characterised by different climatic conditions. Experimentation in the two fields involved a 3-year survey during the growing seasons 2009, 2010, and 2011, where the adult populations of maize leafhoppers were monitored from the sowing of maize plants to the end of the phenological stage at which they are most susceptible to D. maidis activity. Results showed a good response of the model in describing maize leafhopper populations, also allowing the possibility of setting a threshold for intervention and a projection of the situation if any control action is applied.Fil: Rossini. Luca. Università degli Studi della Tuscia; ItaliaFil: Virla, Eduardo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Luft Albarracin, Erica Beatriz. Fundación Miguel Lillo. Dirección de Zoología. Instituto de Entomología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Van Nieuwenhove, Guido Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Speranza, Stefano. Fundación Miguel Lillo. Dirección de Zoología. Instituto de Entomología; Argentin