Evaluating the potential of RNA interference for control of striped cucumber beetle, Acalymma vittatum (Fabricius) (Coleoptera: Chrysomelidae)

TL;DR

This study explores RNA interference as a method to control striped cucumber beetles, finding it effective when injected but less so when delivered orally.

Contribution

The study is the first to evaluate RNAi for controlling striped cucumber beetles and investigates factors affecting oral RNAi efficiency.

Findings

Injected dsRNA caused significant gene knockdown and mortality in striped cucumber beetles.

Oral delivery of dsRNA was less effective, even after knocking down gut nucleases.

Digestive fluid differences between beetles suggest species-specific RNAi efficiency.

Abstract

The striped cucumber beetle (SCB) is a serious pest of cucurbit crops, causing damage both by feeding on plants and by vectoring plant diseases. Cultural, biological and chemical methods are currently used for its management, however, RNA interference (RNAi) as a potential control strategy, has not yet been evaluated.

Injecting dsRNA into the hemocoel of adult SCB resulted in significant gene knockdown and mortality for all seven genes tested (v‐ATPaseA, rpt3, rop, α‐snap, srp54k, β‐actin and α‐tubulin). However, oral delivery of the three dsRNAs found to be most lethal using injections, targeting β‐actin, α‐snap and rpt3, led to less efficient gene knockdown and mortality than injections. In silico analysis of the SCB transcriptome revealed the presence of five dsRNA‐degrading nucleases, of which dsRNase5 had the highest expression in the gut. However, double knockdown of dsRNase5 and the rpt3 gene did not improve oral RNAi. Comparing dsRNA stability in digestive fluid and hemolymph of SCB and Colorado potato beetle (CPB) revealed differences in dsRNA‐degrading nuclease activity. Furthermore, oral RNAi of the β‐actin gene in CPB adults resulted in 100% mortality, whereas mortality was only 33.3% in SCB.

Although SCB has a robust RNAi response to injected dsRNA, oral RNAi works less efficiently. Knockdown of the most highly expressed dsRNase gene in the SCB gut did not enhance oral RNAi. This suggests nucleases may not be the main reason for the reduced oral RNAi efficiency in SCB and other factors are likely to be involved. © 2025 His Majesty the King in Right of Canada. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. Reproduced with the permission of the Minister of Agriculture and Agri‐Food.

SCB has a robust RNAi response to injected dsRNA, but oral RNAi is less efficient. Nucleases do not appear to be responsible for the discrepancy, suggesting other factors are involved.

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