苹果园二斑叶螨的经济为害水平

二斑叶螨是为害苹果的重要害螨。为经济有效地控制其为害，通过田间调查二斑叶螨种群动态，利用螨日（MD）和苹果的产量损失率建模，研究了苹果树上二斑叶螨的经济为害水平（EIL）。结果显示，苹果的产量损失率与二斑叶螨的螨日具有显著相关性，并据此建立了螨日与产量损失率的回归方程：Q=0．0157＋0．00016MD，R2=0．9567。在经济允许损失率为4．57％时，若以虫口密度作为经济允许为害水平的评价方法，则7月3日之前的EIL≤7．70头／叶，7月25日之前的EIL≤8．70头／叶；当以累计螨日评价时，7月3日之前累计螨日≤29．93，7月25日之前累计螨日≤122．95，在整个生长季的累计螨日需低于188．70。

The economic injury level caused by Tetranychus urticae at apple orchard

Tetranychus urticae is one of the most important pests in fruit production.For the sake of economically and effective control the damage,the investigation was carry out to find its population dynamics and apple’s yield loss,the concerns model was established hereby.And then,the economic injury level(EIL) based on T.urticae in apple orchards was studied.The results show that there were significant correlation between the mite days(MDs) and apple yield losses(Q=0.0157+0.00016MD,R2=0.9567).When the economic tolerable injury level is 4.57%,if the mite’s population density of per leaf as evaluation methodology,the EIL should be ≤7.70 per leaf before early July 3th,and ≤8.70 per leaf before July 25.When the accumulative MDs as evaluation methodology,the EIL should be ≤29.93 before early July 5th and EIL≤122.95 before July 25.The total MDs should≤188.70 in the whole growing season.