Baculoviruses are widely used as bioagents for controlling insect populations. Although they are successfully replicated in cell cultures, still the production in laboratory reared larvae is the cheapest way for large-scale production of viral agents. Commercial products are prepared as liquid suspensions and as dried powders. We investigated the stability of two formulations of S. exigua nuclear polyhedrosis virus (SeMNPV) stored at +4°C for over twenty years as a powder (prepared by aceton precipitation) and in a suspension. The biological activity and biochemical properties of these formulations were examinated. Viral biological activity of the suspension was 1 OOO times better than the activity of powdered virus. Aceton precipitation method caused the significant loss of virus activity. Electrophoretic analysis of proteins showed degradation of polyhedrin peptide. There was also partial DNA degradation. These changes may lead to decreased bioactivity of powdered SeMNPV virus.

A nucleopolyhedrovirus isolated from the beet armyworm Spodoptera exigua (Polish laboratory culture), SeMNPV (P), morphologically similar to the viral bioinsecticide virus Spod-XR, was characterized molecularly and biologically. Phylogenetic analysis based on three conserved baculovirus genes, polh, lef-8 and pif-2, showed the highest homology of SeMNPV (P) to Mamestra brassicae (Mb) MNPV and M. configurata (Maco) MNPV, and much less to SeMNPV (Spod-XR). These findings were confirmed by genomic DNA restriction profile analyses. Bioassays revealed that SeMNPV isolated from the commercial bioinsecticide Spod-X^R was themost infectious for S. exigua, while the infectivity of SeMNPV (P) and MbMNPV was significantly lower. These data suggest that SeMNPV (P) is a variant of MbMNPV.

Our research provides novel information concerning the insecticidal activity of Brassica alba mustard oil applied to the intestinal tract via insects’ diet against pests from the order Lepidoptera: Cydia pomonella, Dendrolimus pini, and Spodoptera exigua. The LC50 value of the oil against C. pomonella was 0.422 mg ⋅ ml–1. The LC50 of the plant oil against D. pini was 11.74 mg ⋅ ml–1. The LC50 of the botanical product against S. exigua was 11.66 mg ⋅ ml–1. The plant substance was the most active against C. pomonella in comparison with D. pini and S. exigua. The LC50 values of the oil against D. pini and S. exigua were similar. The plant oil exhibited high insecticidal activity against pests from the order Lepidoptera and may prove to be an effective biopesticide.