Insecticidal activity of soursop leaves (Annona muricata L.) against Sitophilus zeamais

Abstract

The varied behavioral and physiological responses which insects express against various synthetic and natural toxins convey how it influences pest behavior and reflects the toxin's mode of action. Insects show resistance through behavioral mechanisms that reduce their subjection to insecticides and through the evolution of physiological mechanisms allowing them to deal with high insecticide levels in or on the body [1]. The conditions of relatively high humidity and temperature in tropical and subtropical countries are ideal for cultivating several grain types as well as for the large-scale propagation of all kinds of insects that can cause unsatisfied storage infrastructure for the grain stocks [2]. The harmful effects on the environment and health, greater selection pressure and the increment in the genetically resistant strains to the insecticidal active ingredients, and undesirable failures in supply and control management systems have been identified as the major limitations of the endless usage of synthetic insecticides. To get rid of these issues, discovering efficient methods for pest control is necessary. Therefore, it is essential to find out new substances that will fulfill the requirements of toxicological safety, low environmental impact, and agronomic efficiency for the beneficial control of insect pests of stored grains [3]. Recent investigations have proven that the efficiency of plant extracts as promising stored-grain protectants and several bioactive compounds which can be used as alternative insect control agents have been recovered. Phytochemical pesticides are advantageous for providing novel modes of action against insects that can reduce the risk of cross resistance as well as offering new leads for designing target-specific molecules [4-6]. According to the literature of Annona muricata L., although the seed is reported to have strong insecticidal effects, the leaves have not yet been recommended as the chemical and nutritional contents in recent times. Therefore, the current study has been conducted to separate the bioactive compounds according to the polarity and evaluate the bioactivity of methanol extract and fractions obtained from A. muricata leaves against Sitophilus zeamais Motschulsky which is the main pest species of stored cereals in tropical conditions with the aim of discovering new eco-friendly natural insecticides.