Studies On The Control Effect Of Delphastus Catalinae To Bemisia Tabaci

Delphastus catalinae (Horn), originating in North America, is an importantpredators of whitefly. This paper discusses research on the predation functionresponses and the autointerference effects by D. catalinae on Bemisia tabaci eggs indifferert temperature and humidity conditions, and the effects of temperature stress onD. catalinae, as well as the best proportion of benefit to harm for releasing D.catalinae in greenhouse. It provides some references for application of D. catalinae inthe fields. The research results are mainly as follows:1. The predation of D. catalinae on B. tabaci eggs was in accord with the HollingtypeⅡdisc equation. In the same condition of temperature and humidity, the predationof D. catalinae increased with the increase of prey density, while the searching effectsdecreased with the increase of prey density. The predation increased with the increaseof temperature in the range of15℃-27℃, while the predation decreased with theincrease of temperature in the range of27℃~35℃. The predation increased with theincrease of humidity in the range of15%~75%, while it decreased with the increase ofhumidity in the range of75%~95%. The average predation amount of D. catalinae onB. tabaci eggs reduced with their own increased density in different temperature andhumidity. The competition of predation by male and female D. catalinae on B. tabaciwas sharing competition, and with the logarithm value increase of their own density,the sharing competition increased as linear.2. The mortality rate of D. catalinae increased with prolonging of exposure timeat the same temperature; and which was also increased with the increase of exposuretemperature at the different temperature. The death time of the female D. catalinaewas earlier than the male, and the time for50%individuals death (LTime50) offemale D. catalinae was smaller than the male one. In the case of1h high temperatureexposure, the temperature for50%individuals death (LTemp50) of female and male D.catalinae was42.505℃and42.875℃respectively, which proved that the heatresistance of the male was higher than the female. The best acclimation temperature of female and male D. catalinae was36℃and34℃respectively, and the mortalityreduced from80.00%and78.33%to41.67%and28.33%respectively. Thesupercooling point was not difference distinctly between female and male D.catalinae, with-12.41℃and-12.27℃respectively, but the difference distinctlybetween the larva and adult. Domestication at6℃did not significantly reduce theSCP of D. catalinae, however some increased.3. D. catalinae played a good role in control in the egg stage of B. tabaci.According to the ratio of1:400of D. catalinae: B. tabaci to release D. catalinae, thecontrol effect could reached to71.10%on30days after released, but in the thirdnymph stage of B. tabaci, it came to only61.93%. As well as in the egg stage, thecontrol effect reached to53.79%under the D. catalinae releasing proportion of1:1000. The test in the greenhouse showed that only given the better control of thereleasing time and ratio, the better control effect could be received.