Stady on the different instars of Stethorus punctillum to the varying stage of Tetranychus truncatus
[Objective]To study the predation function response of Stethorus punctillum Weise to Tet-ranychus truncatus Ehara,and to clarify the predation effect of S.punctillum on different forms of T.truncatus,This study provided theoretical basis and technical support for the comprehensive management of T.truncatus in the field and the utilization and exploitation of natural enemy resources.[Methods]With T.truncatus as prey,we studied the predation of S.punctillum under different predation states and different density combina-tions of T.truncatus.[Results]The predation function types of S.punctillum to each form of T.truncatus be-longed to Holling-Ⅱ type.The predation capacity of the fourth instar larvae was the strongest.The daily maxi-mum predation capacity of the fourth instar larvae(90.91)was 23.09 times of that of the second instar larvae(3.94)and 4 times of that of the third instar larvae(22.73),followed by female adults,male adults,second instar larvae,and first instar larvae.The search effect of S.punctillum on T.truncatus decreased with the in-crease of prey quantity,and increased with the increase of age of S.punctillum.When the prey species were a-dult,if and juvenile mites,the search effects of the fourth instar larvae and female adults were similar,and both were greater than those of other insect states.[Conclusion]The fourth instar larva and the adult of S.punctillum preys more prey on the T.truncatus and have similar damage control ability.
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