七星瓢虫对苜蓿斑蚜捕食作用的研究

七星瓢虫(Coccinella septempunctata)捕食苜蓿斑蚜(Therioaphis trifolii)的数量与苜蓿斑蚜密度呈负加速曲线关系,功能反应符合Holling-Ⅱ型模型,为N_a=1.024 2N/(1+0.003 3N),捕食苜蓿斑蚜的数量随斑蚜密度增加而增大,但寻找效应随之而降低,日最大捕食量为313头。在10～25℃下,七星瓢虫捕食率y与温度x的关系为y=2.4 1x+3 0.0 7 5,在2 5～3 5℃间的捕食率y与温度x的关系为y=1 2 0-1.2x,2 5℃下七星瓢虫捕食率最高,捕食率达9 0.5%。在种内干扰条件下,其捕食作用率E随天敌密度P的增加而减少,干扰反应数学模型为E=0.4 1 9 3P^{-0.5 0 1 8}。随着叶片数量增多,七星瓢虫和斑蚜之间的距离相对增大,造成捕食率的下降。

Studies on predation of Coccinella septempunctata on Therioaphis trifolii

The functional response of Coccinella septempunctata to Therioaphis trifolii fitted Holling-Ⅱtype equation: N_a=1.024 2N /(1 + 0.003 3N).The relationship between the quantity of spotted aphids preyed by ladybirds and the density of spotted aphids could be represented by a negative accelerative curve.The searching efficiency decreased with the increase of the spotted aphid density.The daily maximum number of spotted aphids preyed by a ladybird was theoretically 313.At the range of 10-25 ℃,the relationship between the predation ratio(y) and temperature(x) was y=3.4x-7.937 5,but at 25-35 ℃,the relationship became y=120-1.2x.The predation ratio was the highest at 25 ℃,up to 90.5%.Under intraspecific interference,the predation ratio(E) decreased with the increase of natural enemy density(P).The natural interference equation was E = 0.419 3P^{-0.501 8}.The results also showed that the relative distance between the ladybirds and spotted aphids enlarged with the increase of alfalfa leaves,which led to the decrease of predation ratio.This research may provide the scientific basis for controlling alfalfa spotted aphids with C.septempunctata.