Urban herbicide use threatens a non-target butterfly (Hypolimnas misippus) through direct toxicity and host plant stress in Ghana
6 affiliations
- 1Department of Conservation Biology and Entomology, University of Cape Coast, Cape Coast, Ghana
- 2Department of Agricultural Economics and Extension, University of Cape Coast, Cape Coast, Ghana
- 3Department of Crop Science, University of Cape Coast, Cape Coast, Ghana
- 4Department of Economics, University of Cape Coast, Cape Coast, Ghana
- 5Laser & Fibre Optics Centre, Department of Physics, University of Cape Coast, Cape Coast, Ghana
- 6Department of Biomedical Sciences, University of Cape Coast, Cape Coast, Ghana
Abstract
Urban residential areas are increasingly managed using herbicides, yet the ecosystem-level consequences of this practice remain poorly understood, particularly in sub-Saharan Africa. This study examined urban weed management practices in Ghana and assessed how commonly used herbicides influence plant–insect interactions focusing on the butterfly, Hypolimnas misippus, and its larval host plant, Portulaca quadrifida. A household survey of 600 participants across twelve urban towns in Ghana’s Central Region showed that herbicides are the dominant method of weed control, with glyphosate- and paraquat-based formulations most frequently used. Laboratory no-choice bioassays were conducted to evaluate the effects of field-recommended concentrations of glyphosate, paraquat, and haloxyfop-methyl on butterfly eggs and larvae. In parallel, herbicide-induced physiological stress in P. quadrifida was quantified using laser-induced chlorophyll fluorescence (LICF) induction kinetics. Paraquat caused acute toxicity, resulting in complete larval mortality within 24 h and near-total egg mortality (96%). Haloxyfop-methyl substantially reduced survival and adult emergence, with mortality occurring across larval and pupal stages. Glyphosate did not significantly affect survival but, slightly prolonged development time. LICF measurements revealed pronounced reductions in leaf vitality indices (Rfd-685 and Rfd-740) following paraquat and haloxyfop-methyl exposure, indicating impaired photosynthetic performance and host plant stress. Together, these results demonstrate that routine herbicide use in urban residential environments can disrupt plant–insect interactions through both direct toxicity and, plant-mediated effects. Such disruptions may compromise urban ecosystem functioning and biodiversity, underscoring the need to integrate ecological considerations into urban weed management strategies. Author summary: Urban residential landscapes are increasingly shaped by the routine use of herbicides to control weeds, yet the ecological consequences of this practice are rarely evaluated. In this study, we investigated how commonly used urban herbicides affect interactions between plants and insects by focusing on a widespread butterfly (Hypolimnas misippus) and its larval host plant (Portulaca quadrifida) in Ghana. We found that herbicides are the primary weed management tool in urban households, and that some widely used products can directly kill butterfly eggs and larvae or indirectly reduce survival by inducing physiological stress in host plants. These findings show how everyday chemical use in cities can disrupt plant–insect interactions that underpin urban biodiversity. Understanding these pathways is essential for managing urban ecosystems in ways that balance weed control with the conservation of ecological functions in rapidly urbanizing regions.
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BibTeX
@article{kudom2026urban,
title = {{Urban herbicide use threatens a non-target butterfly (Hypolimnas misippus) through direct toxicity and host plant stress in Ghana}},
author = {Andreas A. Kudom and Martin Bosompem and Michael O. Adu and Benedict Afful Jr. and Benjamin Anderson and Francis Armah and Paul A. Asare and Joana Ayettey and Ben A. Mensah and Peter Osei-Wusu Adueming},
journal = {PLOS Ecosystems},
year = {2026},
month = sep,
doi = {10.1371/journal.pesy.0000020},
url = {https://doi.org/10.1371/journal.pesy.0000020},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Urban herbicide use threatens a non-target butterfly (Hypolimnas misippus) through direct toxicity and host plant stress in Ghana
AU - Andreas A. Kudom
AU - Martin Bosompem
AU - Michael O. Adu
AU - Benedict Afful Jr.
AU - Benjamin Anderson
AU - Francis Armah
AU - Paul A. Asare
AU - Joana Ayettey
AU - Ben A. Mensah
AU - Peter Osei-Wusu Adueming
PY - 2026
DA - 2026/09/08
JO - PLOS Ecosystems
DO - 10.1371/journal.pesy.0000020
UR - https://doi.org/10.1371/journal.pesy.0000020
AB - Urban residential areas are increasingly managed using herbicides, yet the ecosystem-level consequences of this practice remain poorly understood, particularly in sub-Saharan Africa. This study examined urban weed management practices in Ghana and assessed how commonly used herbicides influence plant–insect interactions focusing on the butterfly, Hypolimnas misippus, and its larval host plant, Portulaca quadrifida. A household survey of 600 participants across twelve urban towns in Ghana’s Central Region showed that herbicides are the dominant method of weed control, with glyphosate- and paraquat-based formulations most frequently used. Laboratory no-choice bioassays were conducted to evaluate the effects of field-recommended concentrations of glyphosate, paraquat, and haloxyfop-methyl on butterfly eggs and larvae. In parallel, herbicide-induced physiological stress in P. quadrifida was quantified using laser-induced chlorophyll fluorescence (LICF) induction kinetics. Paraquat caused acute toxicity, resulting in complete larval mortality within 24 h and near-total egg mortality (96%). Haloxyfop-methyl substantially reduced survival and adult emergence, with mortality occurring across larval and pupal stages. Glyphosate did not significantly affect survival but, slightly prolonged development time. LICF measurements revealed pronounced reductions in leaf vitality indices (Rfd-685 and Rfd-740) following paraquat and haloxyfop-methyl exposure, indicating impaired photosynthetic performance and host plant stress. Together, these results demonstrate that routine herbicide use in urban residential environments can disrupt plant–insect interactions through both direct toxicity and, plant-mediated effects. Such disruptions may compromise urban ecosystem functioning and biodiversity, underscoring the need to integrate ecological considerations into urban weed management strategies. Author summary: Urban residential landscapes are increasingly shaped by the routine use of herbicides to control weeds, yet the ecological consequences of this practice are rarely evaluated. In this study, we investigated how commonly used urban herbicides affect interactions between plants and insects by focusing on a widespread butterfly (Hypolimnas misippus) and its larval host plant (Portulaca quadrifida) in Ghana. We found that herbicides are the primary weed management tool in urban households, and that some widely used products can directly kill butterfly eggs and larvae or indirectly reduce survival by inducing physiological stress in host plants. These findings show how everyday chemical use in cities can disrupt plant–insect interactions that underpin urban biodiversity. Understanding these pathways is essential for managing urban ecosystems in ways that balance weed control with the conservation of ecological functions in rapidly urbanizing regions.
SN - 3070-8141
ER -