CHAPTER ONE

INTRODUCTION

1.1   Background of the Study

The development of organic chemistry took place along with the study of plants, mainly in the 19th century, when the first studies on plants were scientifically recorded. This ended up in the isolation of some active compounds from plants . It is the vegetal kingdom that has contributed, in a more meaningful way, to the supply of useful substances for the treatment of human diseases.[1]

Hyptis Suaveolens (Lamiaceae) is a fast-growing perennial herb found in dense clumps along roadsides, in over-grazed pastures and around stockyards in the tropics. It’s branched, semi-woody stems can reach a height of 2m, and the plant gives off a characteristic minty smell when crushed. Originally native to tropical America, it is now considered a weed worldwide. [2]

Hyptis Suaveolens is an erect, annual and aromatic plant that belong to the family Lamiaceae, which is also found in northern Nigeria as Daddoya-ta-daji in Hausa; Efiri in Yoruba and Tanmotswangi-eba in Nupe. It may be found in abandoned farmlands in West Africa especially in northern Nigeria. It is also found in bushes abundant in open and waste land at both low and medium altitude. The leaves of the plant are opposite and ovate, about 4 – 9 cm long, with an obtuse apex, bilateral base and are dorsiventrally arched. The flowers are axillary with long stalk, hairy calyx, and about 4 mm long. The corolla is blue, zygomorphic and bilabiate. The stamens are four, diclinate and about 8 mm long, the seeds are flat and mucilaginous. A decoction of the leaf is used by traditional healers in Northern Nigeria, especially around Niger, Nassarawa, and Kaduna States in the treatment of diabetes mellitus and fever associated with cold among others. It is also used as an aromatic herb by traditional healers. This herb holds a reputed position among the traditional healers that are expert in the treatment of different types of cancers in India. Its different parts are used both internally and externally for dermatitis and eczema. The leaves of the plant have been shown to contain alkaloids, terpenes and volatile oils.[3]

The conventional use of synthetic insecticides for the control of bean weevils and aphids is associated with certain drawbacks. However the interest in insecticides of plant origin has been enhanced by the current public suspicion of any chemical of persistent nature, whether or not evidence is available of any adverse effects. It is established that Hyptis Suaveolens contains compounds that can control insects and nematodes. Thus it is expedient to evaluate the effect of Hyptis Suaveolens parts on the survival and reproduction potential of bean weevils and maize aphids in the search for alternative control method instead of the use of expensive, toxic and imported synthetic insecticides.[4]

Insects infesting stored foods are one of the most common household insect problems. The many different kinds of insects that invade stored dried foods are often referred to as pantry pests." They contaminate more food than they consume, and most people find the contaminated products unfit for consumption. Pantry pests are often discovered when they leave an infested food to crawl or fly about the house. They often accumulate in pots, pans or dishes or on window sills. Fortunately, they do not bite or sting people or pets nor do they feed on or damage the house structure or contents. Nearly all dried food products are susceptible to insect infestation, including cereal products (flour, cake mix, cornmeal, rice, spaghetti, crackers, and cookies); seeds such as dried beans and popcorn; nuts; chocolate; raisins and other dried fruits; spices; powdered milk; and cured meats. Non-food items that may be infested include birdseed, dry pet food, ornamental seed and dried plant displays, ornamental corn, dried flowers, garden seeds, potpourri, and rodent baits.[5]

A stored food product may become infested at the processing plant or warehouse, in transit, at the store, or right at home. Most of the stored food insects also are pests of stored grain or other commodities and may be relatively abundant outdoors. Food products that are left undisturbed on the shelves for long periods are particularly susceptible to infestation. However, foods of any age can become infested.[5]

Since the late 1940s, much of the insect control in the United States has been based on the use of synthetic chemical insecticides. Insecticides are relatively easy to use and have generally provided effective pest control; it is likely that they will always be a component of pest management programs. Unfortunately, insecticides have some undesirable attributes; they usually present some degree of hazard to the application and other people who may come in contact with them; they can leave residues that some find unacceptable, they can contaminate soil and water and affect wildlife, aquatic life, and other non-target organism. They can interfere with beneficial organisms such as pollinating insects and the natural enemies of pests; and insects can develop resistance to insecticides, effectively eliminating those materials as management options. For these reasons, there is growing interest among farmers, horticulturists, and gardeners to explore and adopt methods that reduce pesticide use.[6]

Biological control represents one alternative to the use of insecticides. Biological control is the conscious use of living beneficial organisms, called natural enemies, for the control of insect pests. Virtually all insect pests have natural enemies, and many insect pests can be effectively controlled by managing these natural enemies. Biological control will not control all insect pests but it can be the foundation of an approach called integrated pest management, which combines a variety of pest control methods in an ecologically safe system which include botanical insect control from plant Extract.[6]

1.2       Aim of the Project

The aims of this work is:

Ø  To evaluate the insecticidal potential of Hyptis Suaveolens using different Extracts (Ethanol, n-Hexane and Chloroform).

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