Role of herbicides in the decline of butterfly population and diversity

Abstract

AbstractThe herbicides not only produce a lethal effect on herbs but also indirectly harm those species which use herbs as host plants during their life cycle. The adverse effect of herbicide is comparatively more than any insecticide found in the agricultural industry. Herbicides act as enzyme inhibitors that block the synthesis of essential biomolecules in herbs. Action mechanisms in which herbicides act on the plant body as well as the classification of the herbicides according to their mode of action have been recorded. Lethal effects of herbicides cause qualitative and quantitative losses of herb‐weeds and associated beneficial herbs from crop fields that lead to the decline in diversity of butterfly population. Lack of food sources, alteration of life cycle and morphological anomalies are found as a result of herbicidal interference on enzymatic reactions in butterflies. Beneficial organisms and pollinators are included within the affected ones. We selected the butterfly as it is recognized as a good indicator species. The effects of two graminicide fluazifop‐p‐butyl and sethoxydim, and a surfactant (like ‘Preference’ that help to increase penetration) were evaluated on Icaricia icarioides blackmorei and Pieris rapae in the laboratory. Glyphosate and glufosinate ammonium (GLA) kill milkweed plants (Asclepias sp.) by blocking the 5‐enolpyruvylshikimate‐3 phosphate synthase (EPSPS) enzyme. 2,4,5‐trichlorophenoxyacetic acid (2,4,5‐T), an herbicide used in forest and nature reserves, is toxic to springtails (Onychiurus quadriocellatus) upon direct contact resulting a disastrous effect on Monarch. Fifth instar caterpillars of skipper butterfly Calpodes ethlius die when they are fed GLA‐treated host plants. Atrazine and S‐metolachlor are the two other herbicides which are thought to have a role on milkweed plant whose leaves are the food of the larvae. Triclopyr, sethoxydim, and imazapyr are the three herbicides that reduced the adult emergence of Behr's metalmark butterfly. The objective of the study is to provide precise information regarding the relationship between herbicides and butterflies as well as the recommendation of feasible strategies for butterfly conservation with respect to weed management.