Habrobracon hebetor is a globally acknowledged larval ectoparasitoid that is widely used to control lepidopteran pests. Wolbachia is a natural endosymbiont that regulates various aspects of the insect host biology. The ability of H. hebetor to paralyze and develop on lepidopteran larvae from five families was tested under laboratory conditions. Two lines of the wasp were used, “W+” containing a naturally occurring Wolbachia from the supergroup B, and “W−”, with the endosymbiont eradicated by antibiotic treatment, followed by propagation of 20 subsequent generations. The proportions of larvae in which host paralysis, as well as parasitoid oviposition, larval, pupal, and adult development were observed, were usually higher in W+ compared to W−. In Loxostege sticticalis, differences in these indices were not statistically significant. In Galleria mellonella, Mamestra brassicae, and Ostrinia nubilalis, some of the parasitism indices were significantly higher in W+ than in W−. In Bombyx mori and Plutella xylostella, H. hebetor could not complete its life cycle, but parasitism levels at the initial steps (from paralysis symptoms to the presence of larvae/pupae of the parasitoid) were 2–5 times lower in W− compared to W+ (p < 0.01). It can be suggested that the presence of Wolbachia is advantageous for H. hebetor, as it increases the success of parasitism in a broad range of lepidopteran hosts.

Trichogramma is an important genus of egg parasitoids, applied against agricultural and forest lepidopteran pests. Known species differ in host specificity, which affects both their efficiency in field and suitability for mass rearing. In 2022, a novel strain of T. dendrolimi was recovered from eggs of the Siberian silk moth Dendrolimus sibiricus in Eastern Siberia. Freshly laid eggs of lepidopteran insects belonging to 17 species were exposed to adult T. dendrolimi. Besides the original host, successful reproduction was observed in the eggs of 13 species belonging to the families of Sphingidae (3 species), Noctuidae (2 species), Pyralidae (1 species), Crambidae (1 species), Erebidae (3 species), Gelechiidae (1 species), Geometridae (2 species), Nolidae (1 species), and Lasiocampidae (3 species). The maximum parasitoid yield of 33 adults per egg was observed in D. sibiricus, followed by Dendrolimus pini (32 adults/egg), Macrothylacia rubi (27 adults/egg), Manduca sexta (26 adults/egg), Orgyia antiqua (4 adults/egg), Pseudoips prasinana (3 adults/egg), Mamestra brassicae, Angerona prunaria, and Chrysorithrum flavomaculata (2 adults/egg), as well as Hydraecia micacea, Ostrinia nubilalis, Galleria mellonella, and Sitotroga cerealella (1 adult/egg). Thirty generations were successfully reproduced in the laboratory using D. sibiricus, M. sexta, M. brassicae, and S. cerealella eggs. The parasitoid remained viable and efficiently attacked eggs of various lepidopteran hosts. The present study extends the knowledge of susceptible hosts of T. dendrolimi. Some of these host species provide high reproduction indices of the parasitoid and could be used for large scale propagation of this biocontrol agent.

The use of viruses as natural pathogens of pest insects is a promising approach in biocontrol. The main drawback of this approach is its relatively slow mode of action, which could be addressed through genetic modifications of the strains used. In this article, we propose the use of the commercially available Bac-to-Bac system for infecting pest insects with a recombinant virus and assessing the impact of various molecules on their viability. Using the laboratory-friendly model organism Galleria mellonella and baculovirus carrying the eGFP gene, we demonstrated a 100% infection rate, with a consistent and stable spread of the viruses throughout insect bodies and a gradual increase in recombinant protein expression. Notably, at day 5 post-infection the insects remained viable and active. This approach enables the identification of pathogenic effects caused by the virus-induced expression of other molecules, such as toxins.