七星瓢虫对不同初始密度棉蚜种群的调控作用

Regulation of Coccinella septempunctata and Aphis gossypii with different initial density on cotton aphid population

为明确七星瓢虫成虫对棉蚜的自然控制能力,本文通过密度-天敌双因素控制试验分析了不同棉蚜初始密度(200头/株、400头/株、800头/株)和不同七星瓢虫数量(0头、1头、2头、4头)组合处理下棉蚜的种群动态;使用棉蚜种群增长率、益害比、控制效果等指标评估了天敌的控制能力,并建立简单的模型来明确天敌有效控制棉蚜的益害比。结果表明,七星瓢虫和棉蚜初始密度显著影响着棉蚜的种群数量,且两者存在交互作用;益害比与控制效果存在显著的正相关性,种群增长率与控制效果又存在显著的负相关性。投放七星瓢虫5 d后,当益害比达到1∶720以下时,七星瓢虫可有效控制棉蚜(种群增长率r≤0),此时控制效果达44%以上;此外,当益害比为1∶671时,七星瓢虫对棉蚜种群的控制效果达50%,益害比低于1∶360以下时,七星瓢虫对棉蚜种群的控制效果可达80%以上。因此,本文通过控制试验建立了七星瓢虫成虫控制棉蚜的防治指标,可以依据该阈值来指导田间棉蚜的综合防治。

In order to determine the control effect of seven spotted ladybird beetles Coccinella septempunctata adults on cotton aphid Aphis gossypii,two-factor control experiments were implemented.The population of cotton aphids were monitored inside cages with different initial densities(200 individuals/plant,400 individuals/plant,800 individuals/plant)and different numbers of seven spotted ladybird beetles(0,1,2,4),and compared with a control group.The control ability of natural enemies was evaluated by population growth rate of cotton aphid,predator-prey ratio and control efficiency.The simple model was developed to confirm the predator-prey ratios from natural enemies of effective control to cotton aphid.The results showed that the population of cotton aphids was significantly affected by its initial density and the number of seven spotted ladybird beetles,and an interaction effect was detected between the two factors.There was a significant positive correlation between the predator-prey ratios and control efficiency,while a significant negative correlation between population growth rate and control efficiency was found.In addition,the seven spotted ladybird beetles could effectively control cotton aphids after released inside cages for 5 days(population growth rate r≤0),and led to a control efficiency of 44%when the predator-prey ratios reached below 1∶720.Similarly,control effect rose to 50%and 80%when the predator-prey ratios reached as low as 1∶671 and 1∶360,respectively.In conclusion,this study established the control threshold that adults of seven spotted ladybird beetles prey on cotton aphids through controlled experiment,which can be used to guide integrated control of cotton aphid in the field.