Predation and Preference of Orius maxidentex Ghauri on Scirtothrips dorsalis Hood
The control potential of Orius maxidentex Ghauri against Scirtothrips dorsalis Hood was evaluated through investigating the predation ability and selectivity of O.maxidentex in laboratory.The results showed that the first instar nymphs of O.maxidentex did not predate on S.dorsalis,whereas the second instar nymphs predated on a small number of the first and second instars of S.dorsalis.From the third instar nymphs to adults,O.maxidentex predated on all stages of S.dorsalis.The predation of O.maxidentex on the second instar nymphs and adults of S.dorsalis ranked from high to low was fifth instars,adults,fourth instars,and third instars.The daily maximum predation of the fifth instar O.maxidentex on the 2nd instar nymphs and adults of S.dorsalis were 31.60/d and 30.80/d,respectively.The predation of O.maxidentex from the third instar nymphs to adults on S.dorsalis fitted well with the Holling Ⅱ functional response model.The predation increased with the increase of prey density,and the search efficiency decreased with the increase of prey density.The disturbance response was consistent with the Hasse Ⅱ model equation.At a certain S.dorsalis density,the predation of an individual O.maxidentex decreased gradually with the increase of its self-density.The preference coefficient of O.maxidentex from the 3rd instar nymphs to adults for the first instar S.dorsalis nymphs was greater than 0(Ci＞0),whereas that for S.dorsalis adults was smaller than 0(Ci＜0).The results of present study show that O.maxidentex prefer to prey on the young nymphs of S.dorsalis.
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