Exploitation of Semiochemicals for the Management of Pest and Beneficial Insects with Special Emphasis on Cotton Cropping Systems in Australia: A Review

This paper examines semiochemicals, substances or mixtures of substances produced by one species that influence the behaviour of receptor organisms, from the perspective of their potential in a sustainable pest management context. Particular reference is made to Helicoverpa spp. and their natural enemies on cotton and to those chemical components derived from the inner tissues and organ surfaces of plants The post-alightment behavioural sequence of insect pests such as Helicoverpa spp. which lay eggs on plants which are not a food source, includes the sensing of small quantities of many types of chemical substances that may include free amino acids, organic acids, sugars, secondary metabolites, vitamins, minerals, growth regulators, etc. Detection of these substances on the leaf or organ surfaces of the plant provides specific information to the female insect on plant health, physiology and nutrition that guides the insect to either accept or reject the plant for oviposition. Three behaviour manipulation methods for pest management have been identified as (1) a behaviour of the pest, (2) a means by which the behaviour is manipulated appropriately, and (3) a method that utilizes the behavioural manipulation method for the protection of the resource from the pest. Stimuli that act over long distance such as chemical stimuli (e.g. attractants and repellents) and visual stimuli influence the insect's encounter with the plant. After the insect has landed, short range stimuli such as stimulants and deterrents, which occur on the organ or leaf surfaces of the plant, guide the insect to either accept or reject the plant for oviposition or feeding. In terms of beneficial insects, stimuli that act over long distances (eg. Food spray products) can be used to attract and conserve natural enemies of pests, enhancing their effectiveness as pest control agents. Food spray products attract natural enemies to an area through volatile compounds emitted by the products to increase the predator to prey ratio, predator searching activity and predation of pests in the cropping system. There is potential for plants which are not normally encountered by pest or beneficial insect species to function as a source of behaviour-modifying chemical signals, perhaps having different effects on different pests and beneficial insects. In general, semiochemicals are inherently different from synthetic insecticides in terms of their efficacy and impact on the environment and human health.