Insecticidal and Histopathological Effects of Ageratum conyzoides Weed Extracts against Dengue Vector, Aedes aegypti.

Sumate Ampawong,Jiraporn Ruangsittichai,Patchara Sriwichai,Supaluk Popruk,Ai-rada Pintong,Narumon Komalamisra

doi:10.3390/insects11040224

Sumate Ampawong, Jiraporn Ruangsittichai + Show 4 more

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https://doi.org/10.3390/insects11040224

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Abstract

Crude extracts and essential oils of A. conyzoides were tested with larva and adult stages of Ae. aegypti mosquitoes to determine their insecticidal properties. The crude extracts and essential oils came from three varieties of A. conyzoides (with white flowers, purple flowers, or white-purple flowers) and from two places on each plant (leaves and flowers), giving six types overall: leaf-white (LW); leaf-purple (LP); leaf white-purple (LW-P); flower-white (FW); flower-purple (FP); and flower white-purple (FW-P). Chemical constituents and components of the essential oils were identified using gas chromatography-mass spectrometry (GC-MS). Electron microscopic and histopathological studies were performed to determine the toxicological effects on mosquitoes in terms of morphological alterations. The six types of crude extracts exhibited no activity against individuals in the larval stages. However, six types of essential oils were effective against adult Ae. aegypti females. The mortality of adult Ae. aegypti females was higher from leaf extracts, particularly LP (median lethal dose, LD50 = 0.84%). The number of chemical constituents identified by GC-MS was high in flowers, especially W-P. Precocene I was the most abundant chemical component among the five types of essential oils, except in LP, in which precocene II was the most abundant. Histopathological alterations in adult Ae. aegypti females included compound eye degeneration, muscular damage with cellular infiltration, gut epithelial degeneration and necrosis, pyknotic nuclei in the malpighian epithelium and ovarian cell degeneration. FW and FP plant types exhibited the highest severity of histopathological alterations in mosquitoes compared with other plants, probably owing to the presence of monoterpene compounds in their tissues. The present study demonstrated LP plant extracts from A. conyzoides could be effective adulticides against adult Ae. aegypti. As natural products are biodegradable and exhibit low toxicity to mammalian and non-target organisms, they are suitable candidates for use in vector control programmes.

Highlights

IntroductionThe incidence of dengue infections worldwide is approximately 390 million people every year [1]
Dengue is currently widespread throughout subtropical and tropical regions
Vector control programmes largely depend on the use of synthetic insecticides, which has been sustained over many decades, consistently using synthetic pesticides could lead to ineffective control due to the development of insecticide resistance in Ae. aegypti in many countries worldwide, such as Indonesia, India, Malaysia, Thailand, China, Mexico, Columbia and Brazil [4,5]

Summary

Introduction

The incidence of dengue infections worldwide is approximately 390 million people every year [1]. One of the alternative ways to control larva and adult mosquitoes is using natural plant-derived products as pesticide candidates and enhancing the efficacy of chemical pesticide [6,7]. Such products are non-persistent and non-toxic to humans and have shorter environmental persistence than synthetic insecticides, in addition to varying sites of action, which have not been previously reported in mosquito resistance [8,9]

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