Abstract

YASEM DE ROMERO, Marta G.; ROMERO, Eduardo R.; SOSA GOMEZ, Daniel  and  WILLINK, Eduardo. Evaluation of baculovirus strains to control the fall armyworm, Spodoptera frugiperda (Smith, 1797) (LEP.: NOCTUIDAE), a key corn pest in North Western Argentina. Rev. ind. agric. Tucumán [online]. 2009, vol.86, n.2, pp.7-15. ISSN 1851-3018.

Chemical insecticides are used for Spodoptera frugiperda control, a key pest affecting corn crops in North Western Argentina. These insecticides, however, frequently show low effectiveness. The baculoviruses are a biological alternative to control the fall armyworm. The objective of this research was to assess Nucleopolyhedrovirus native and foreign strains as regards their effectiveness in controlling S. frugiperda. The results showed that S. frugiperda larvae death rate rose with increasing viral concentrations, while viral susceptibility of larvae decreased with insect age. LC₅₀ (lethal concentration for 50% of the tested sample) of 7.6 x 10⁴ and 4.5 x 10⁵ polyhedra/ml for three and five day-old larvae, respectively, were determined for the nuclear polyhedrosis virus (NPV) isolated in Leales (Tucumán, Argentina). Similar control levels were determined for the NPV isolated in Oliveros (Santa Fe, Argentina), with lethal viral concentrations (LC₅₀) of 8.6 x 10⁴ and 4.0 x 10⁵ polyhedra/ml, respectively. The Brazilian isolate was characterized by LC₅₀ levels of 5.9 x 10⁵ and 1.5 x 10⁶ polyhedral/ml for three-day-old and five-day-old larvae, respectively. The local isolate (VPNSf -Tucumán) showed the most lethal effect on the native population of young S. frugiperda (three to five-day-old) larvae, with an average lifespan of six days at LC₅₀ levels, while the Oliveros and Brazil isolates showed an average lifespan of seven and nine days, respectively. The VPNSf - Leales isolate was therefore selected as the object of study for this research. Moreover, being a native isolate, it was considered the best alternative from the environmental impact standpoint.

Keywords : Biological insecticides; Fall armyworm; Nucleopolyhedrovirus.

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