| Phenoloxidase (PO) had been shown to be present in organism and it is a key enzyme in the development of insect. As soon as the higer requirement to the environment people focus on the field where they want to find new style pesticides. As time flies the conception of Integrated Pest Mangement (IPM) had been changed to Integrated Agro-ecosystem Management(IAM), that is people do not want to kill all pests but to control the number of them to reduce the lose of agricultural output. In this study, some natural compounds like kojic acid were employed to test if they have the biological activity to diamondback moth Plutella xylostella and to testify if they can inhibit phenoloxidase from the tested insect. In this page,the relationship between biological activity and inhibitory degree of phenoloxidase was also discussed.Several methods were usued as bioassay in the test and the results showed us the contact toxicity or ingestion. In general those compounds did not have high biological activity for the highest death rate was lower than 50%. By topical application on 3rd larva p-hydroxybenzoic acid was found out to have higher biological activity than others but as for 4th larva kojic acid and quercetin can obviously reduce the number of adults appearing. When 2nd larva were dipped in the solution of the compounds, it was found that isoranillic acid was the most effective compound to kill the larva. Also it was p-hydroxybenzoic acid and quercetin that can affect emergence percentage markedly. All compounds except quercetin can hardly prevent eggs from hatching into larvae. By dipping leaves it was found that quercetin can affect growth development of diamondback moth evidently. On the contrary, somelarva after treated were stimulated to add its weight.The results of those compounds' inhibitory degree to phenoloxidase from diamondback moth indicated that all compounds except rutin can inhibit phenoloxidase. The sequence ordered by I50 was showed as below:kojic acid |
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