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Behavioral responses of whitefly, Trialeurodes ricini 's parasitoid, Encarsia formosa to induced plant surface chemicals due to T . ricini infestation of castor, Ricinus communis (L.) plants were studied. The impact of whitefly infestation in the form of quantitative and qualitative changes in the leaf biochemical constituents was also analyzed. The results of Y-tube olfactometer assays performed to investigate the role of pest induced plant semiochemicals in locating host plants by E . formosa showed that whitefly induced plants were not attractive to conspecifics and that the crude surface extracts of infested plants were attractive to the parasitoid when tested against extracts of uninfested plants. Hexane extract of whiteflies was more attractive to E . formosa when tested against surface chemicals of infested plants. The total free amino acids, proteins and the secondary metabolites such as phenols enhanced in whitefly fed plants. On the other hand, total carbohydrate content was reduced in whitefly infested castor leaves over healthy ones. Enzyme analyses after whitefly infestation showed that pest feeding significantly increased the activities of foliar phenyl alanine ammonia lyase (PAL), poly phenol oxidase (PPO) and catalase (CAT). A decrease in superoxide dismutase (SOD) and peroxidase (POD) enzyme activities was evident in pest infested plants. The individual phenolic acids from pest fed plants were identified using high performance liquid chromatography (HPLC) and compared with normal, intact plants. Hence it is concluded that pest infested plants exhibited defense strategies which may be exploited as a tool in the Integrated Pest Management for crop protection. |
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