Effects of copper-based fungicides on the growth and tolerance of Helicoverpa armigera: implications for pest management

Abstract

Heavy metal pollution, particularly from copper (Cu)-based fungicides, has emerged as a major environmental issue. The extensive and frequent use of these fungicides in agriculture, coupled with their persistent residues on plant surfaces, necessitates a comprehensive evaluation of their effects on surrounding organisms. This study specifically targets Helicoverpa armigera larvae to systematically evaluate changes in their viability and ecological fitness in response to excessive Cu²⁺ exposure by simulating field-relevant dosages of Cu-containing fungicides. The results indicate that, at the tested doses, excessive Cu²⁺ treatment had an insignificant impact on the developmental indices of H. armigera larvae. However, it significantly stimulated genetic expression and metabolic activity, notably enhancing the expression of trehalases and detoxification enzymes such as GST, CarE, and CYP450 across various tissues. This metabolic enhancement led to increased food intake in the larvae, thereby strengthening their tolerance to pesticides (azadirachtin, chlorfenapyr, and chlorantraniliprole) under both contact and ingestion toxicity. Moreover, the increased Cu²⁺ exposure reduced the parasitism rate, egg-laying capacity, and host preference of parasitic wasps. Further investigation revealed that H. armigera larvae primarily expel excess Cu through fecal excretion and molting. This study underscores the importance of evaluating the broader ecological impacts of Cu-based fungicides beyond their primary use for pathogen control. The findings provide essential insights into the mechanisms underlying the resurgence of H. armigera and offer theoretical guidance for the rational integration and application of fungicides and pest management strategies.