Effectiveness of two viral isolates on the green worm Lepidoptera: Noctuidae, Spodoptera exigua and striped worm Lepidoptera: Noctuidae, Spodoptera sunia

Abstract

The nuclear polyhedrosis virus is an entomopathogen that has been used to manage noctuidae insects, having a high percentage of effectiveness. The objective of this study was to evaluate the effectiveness of crude nuclear polyhedrosis virus (liquid) in mixtures of two viral isolates, Spodoptera exigua nuclear polyhedrosis virus (SeVPN), Spodoptera sunia nuclear polyhedrosis virus (SsVPN) in their own hosts in field and laboratory conditions. A Randomized Complete Block Design was used with four treatments and four repetitions; The experimental units being the larvae overfed with leaves infested with VPN. The treatments evaluated were: 1) SeVPN virus, 2) SsVPN virus, 3) SeVPN+SsVPN virus mixture (100%) and 4) SeVPN+SsVPN virus mixture (50%). The application of these treatments was carried out using the crude virus (liquid) in each of the sesame cultivation plots in the afternoon. After 24 hours of application, the leaves of the crop were collected from the middle stratum of the plants to be transferred to the virus laboratory of the Center for Research and Reproduction of Biological Controllers of the National Autonomous University of Nicaragua (UNAN, León), where the larvae completed their development. The variable under study was mortality. A normality test analysis was performed for the variable and a post hot was performed according to SNK in SPSS v. 2.1. No statistical differences were determined between treatments, but low mortality values ​​were determined, being 38% for Se+SsVPN100%, 39% for Se+SsVPN50%, SeVPN with 37% and in the case of SsVPN 21%. The low mortality was possibly due to the fact that the study was influenced by biotic factors such as contamination by bacteria and fungi or by the influence of solar radiation in the field.