Effects of Lymantria dispar multiple nucleopolyhedrovirus and Bacillus thuringiensis var. kurstaki on different larval instars of Lymantria dispar asiatica

Abstract

Outbreaks of Lymantria dispar asiatica (the Asian spongy moth; Lepidoptera: Erebidae) occur sporadically, causing widespread damage to forest and fruit trees. Owing to the development of pesticide resistance and environmental contamination, biopesticides, including L. dispar multiple nucleopolyhedrovirus (LdMNPV) and Bacillus thuringiensis var. kurstaki (Btk), can significantly contribute to controlling overall larval stage of this species. Although both pathogens are highly effective at the larval stage, their effects on different instar stages have not been investigated. In this study, we analyzed the mortality and lethality in different L. dispar asiatica instars exposed to single or combined pathogen treatments. Treatments with low or medium LdMNPV concentrations induced lower mortality and had higher LT50 values at the 4th and 5th instars compared with other instars, whereas high LdMNPV treatments induced high mortality in all instars, with higher LT50 values at later instars. Treatment with Btk induced a rapid 100% mortality in all instars, with higher LT50 values for the later instars. The combination of LdMNPV and Btk delayed the killing time compared with the effects of single treatments, with the effect being more pronounced in the 1st and 5th instar stage than at other stages at low Btk concentrations. Our findings indicate that the pathogenic effects of LdMNPV and Btk on L. dispar asiatica differ according to larval stage, thereby providing novel insights into enhancing the biological control efficacy of these agents against L. dispar asiatica in the field.

Effect of fluorescent brighteners on the insecticidal activity of Bacillus thuringiensis var. kurstaki and LdMNPV on Lymantria dispar asiatica in Korea

“…The instars were selected for the experiment 1 day after molting. The larvae ( n = 15) underwent approximately 24 h of starvation before being introduced to the treatment (Hwang et al, 2023). Subsequently, a small droplet (1 µL) of a 20% sucrose solution was provided to the larvae along with three different concentrations of Btk or LdMNPV alone or in combination with a 0.1% concentration of FB (referred to as Btk + FB 28 and Btk + FB 71, LdMNPV + FB 28 and LdMNPV + FB 71).…”

“…Integrated management of the spongy moth has been implemented using chemical control as well as various biological control agents, including entomopathogenic microorganisms such as Bacillus thuringiensis var. kurstaki (Btk) and Lymantria dispar multiple nuclear polyhedrosis virus (LdMNPV) (Hwang et al, 2023;Ruiu et al, 2021).…”

“…Integrated management of the spongy moth has been implemented using chemical control as well as various biological control agents, including entomopathogenic microorganisms such as Bacillus thuringiensis var. kurstaki (Btk) and Lymantria dispar multiple nuclear polyhedrosis virus (LdMNPV) (Hwang et al, 2023; Ruiu et al, 2021). These microbial agents are highly susceptible to the spongy moth and commercially available biopesticides (Arthurs & Dara, 2019; Blackburn & Hajek, 2018; Ruiu et al, 2021).…”