Larvicidal activity of the photosensitive insecticides, methylene blue and rose bengal, in Aedes aegypti and Anopheles gambiae mosquitoes.

Abstract

BACKGROUND:

Insecticides are critical for controlling mosquito populations and mitigating the spread of vector-borne disease, but their overuse has selected for resistant populations. A promising alternative to classical chemical insecticides is photosensitive molecules - here called photosensitive insecticides or PSIs - that when ingested and activated by light, generate broadly toxic reactive oxygen species. This mechanism of indiscriminate oxidative damage decreases the likelihood that target site modification-based resistance evolves. Here, we tested whether the PSIs, methylene blue (MB) and rose bengal (RB), are viable insecticides across the mosquito lineage.

RESULTS:

MB and RB are phototoxic to both Aedes aegypti and Anopheles gambiae at micromolar concentrations, with greatest toxicity when larvae are incubated in the dark with the PSIs for 2 h prior to photoactivation. MB is ten times more toxic than RB, and microscopy-based imaging suggests that this is because ingested MB escapes the larval gut and disperses throughout the hemocoel whereas RB remains confined to the gut. Adding food to the PSI-containing water has a bidirectional, concentration-dependent effect on PSI toxicity; toxicity increases at high concentrations but decreases at low concentrations. Finally, adding sand to the water increases the phototoxicity of RB to Ae. aegypti.

CONCLUSION:

MB and RB are larvicidal via a light activated mechanism, and therefore, should be further investigated as an option for mosquito control. © 2023 Society of Chemical Industry.

• Authors: Cole J Meier, Julián F Hillyer
• Journal: Pest management science (Pest Manag Sci) (Sep 08 2023) ISSN: 1526-4998 [Electronic] England
• PMID: 37682561 (Publication Type: Journal Article)
• Copyright: © 2023 Society of Chemical Industry.