Functional Response Of Harmonia Axyridis To Eriosoma Lanigerm And Aphis Citricola

Apple is an important cash crop in China.Two aphid species,Eriosoma lanigerm Hausmann and Aphis citricola Vander Goot,often occur together and endanger the production of apples,Harmonia axyridis Pallas is a predatory natural enemy of many pests,including E.lanigerm and A.citricola.In order to make clear the comprehensive ecological control effect of H.axyridis on the two aphid species,we studied: 1)The predatory preference of H.axyridis to the two aphids at two densities(4 or 20 aphids per apple seedling for each aphid species);2)the functional response of H.axyridis on E.lanigerm at different temperatures;and 3)comparison of predatory function responses between H.axyridis on A.citricola in indoor and field conditions.In the preference experiment of H.axyridis to the two aphid species,we found that H.axyridis showed no preference when the two aphids were at low density(4 aphids).When both aphids were in high density(20aphids),H.axyridis prefered A.citricola to E.lanigerm.In the functional response of Harmonia axyridis to E.lanigerm at different temperatures(10±1?,15±1?,24±1?),we found that the predation of Harmonia axyridis at 10? was very low,and it was impossible to determine which functional response.Excessive hypothermia can affect the normal predation behavior of H.axyridis.Type ? functional response were present at 15? and24?.At 24?,H.axyridis prey much greater than that at 15? and 10?.The influence of temperature and season should be paid attention to in practical operation in the field,taking into account the effect of low temperature on the predatory efficiency when release H.axyridis.In the laboratory and field greenhouse,predation functional response experiments of the H.axyridis to the A.citricola,we found that in the 2 hour or 24 hour period,H.axyridis prey more A.citricola in the laboratory than in the field.Speculation is due to the high temperature fluctuation in the field,and interference of other insects such as ants,resulting in a low predation in the field.Proving that experiments in the laboratory environment may exaggerate the predatory ability of H.axyridis.All the functional response treatments that can be judged in this study are type II functional response.Predators with type II functional reactions have limited ability to act on high prey density,and it is only possible to effectively control the population of prey when its relative density is low.This study provides some theoretical support for the further use of predatory natural enemies inthe prevention and treatment of pests such as apple aphids.