The Importance Of Insects

1. Introduction:

1.1 Background Information

Insects are the most successful group of animal in the world. They inhabit every terrestrial and freshwater ecosystem. Insects have important roles as plant consumers and herbivores, a food source for other organisms, scavengers and detritivores, predators and parasites. Insects also directly affect human welfare by competing with us for food and transmitting diseases. However, not all insects are detrimental to human welfare. The vast majority of the insects are considered harmless or beneficial (pollinators, predators, parasites, and decomposers). However, pests (those insects that affect man directly or indirectly) get the most publicity. Only about 1 % of the insects are pests. This small number

Rapid reproduction allows aphids to have overlapping generations because of which the preferred developmental stages of aphids are quickly available for parasitism and predation. Aphids being less mobile are more amenable for biological control. They and their honeydew are attractive food sources for many entomopathogens. Nevertheless their physiological activity at low temperature and frequent and rapid changes in their populations make them poor prospects for biological control. Biological control of pests tends to be long lasting and often can be implemented at little direct cost to producers and consumers. For these reasons, biological control is considered as a cornerstone of many Integrated Pest Management (IPM) programmes (Joshi et al.,

Because so many predatory insects are used to control aphids, chemical controls are suggested as a last resort as they kill a variety of insects, including the beneficial ones. Biological control is the use of living organisms to maintain pest populations below damaging levels. Natural enemies of arthropods fall into three major categories: predators, parasitoids, and pathogens (Altieri et al., 2005; Mahr et al., 2008). Non-chemical approaches for management of aphids (Bakhetia and Chandler, 1997) reviewed the management strategies for aphids with special reference to host plant resistance while (Sachan, 1997) reviewed the cultural control of aphids. Recently, Singh (2000) highlighted importance of aphid predators and parasitoids in biological control of aphids. All these workers emphasize the need for alternative methods for effective management of aphids especially in the changing scenario of modern sustainable