Abstract

Synthetic insecticides are generally employed to control the mosquito population. However, their injudicious over usage and non-biodegradability are associated with many adverse effects on the environment and mosquitoes. The application of environment-friendly mosquitocidals might be an alternate to overcome these issues. In this study, we found that organic or aqueous extracts of Agave angustifolia leaves exhibited a strong larvicidal activity (LD50 28.27 μg/ml) against Aedes aegypti, Culex quinquefasciatus, and Anopheles stephensi larvae within a short exposure of 12 h. The larvicidal activity of A. angustifolia is inherited and independent of the plants vegetative growth. Interestingly, the plant larvicidal activity was observed exclusively during the summer season (April–August, when outside temperature is between 30 and 50°C) and it was significantly reduced during winter season (December–February, when the outside temperature falls to ~4°C or lower). Thus, we hypothesized that the larvicidal components of A. angustifolia might be induced by the manipulation of environmental temperature and should be resistant to the hot conditions. We found that the larvicidal activity of A. angustifolia was induced when plants were maintained at 37°C in a semi-natural environment against the controls that were growing outside in cold weather. Pre-incubation of A. angustifolia extract at 100°C for 1 h killed 60% larvae in 12 h, which gradually increased to 100% mortality after 24 h. In addition, the dry powder formulation of A. angustifolia, also displayed a strong larvicidal activity after a long shelf life. Together, these findings revealed that A. angustifolia is an excellent source of temperature induced bioactive metabolites that may assist the preparedness for vector control programs competently.

Highlights

  • Mosquitoes are infamous vectors for numerous life-threatening diseases

  • The larvicidal properties of A. angustifolia were analyzed against A. aegypti, C. quinquefasciatus, and A. stephensi larvae

  • These results revealed that A. angustifolia crude extract in either of the organic solvents is effective to kill A. aegypti larvae in a time-dependent manner

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Summary

Introduction

Mosquitoes are infamous vectors for numerous life-threatening diseases. Synthetic chemicals (insecticides) are mostly employed to control the vector population. The disadvantages associated with their applications warrant the discovery of environment-friendly approaches to control mosquitoes at various stages of their development. Mosquito developmental stages include both aquatic and terrestrial life. Aquatic life starts after the female lays eggs in moist conditions. They further develop into four different stages of instar larvae and into pupae. The relatively long, ~8–10 days, aquatic cycle of mosquito larvae development is considered a potent target for controlling its population. Synthetic larvicidals are mainly employed to achieve this goal [1, 2]. The poor human acceptance of insecticide spray and development of insecticide-resistant mosquitoes are major threats in this area [4]

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