Community Diversity Of Arthropod Predators And Evaluation Of Their Control Efficiency In Cauliflower Field

By investigating population of predators in cauliflower field in natural control, bio-pesticides control and chemical pesticides control in the farm of South China Agricultural University and their functional responses in the lab, we estimated the main predator's predation on target insect pests. The results of this studies were as following:1. There were total of 56 species of predators collected in cauliflower field. The dominant species were spiders, including Lycosa pseudoannulata (Boesenberg et Strand), Pardosa procurva Yu et Song, Coleosoma octomaculatum (Boesenberg et Strand), Propylaea japonica (Thunberg), Menochilus sexmaculatus (Fabricius) et al. The insect pest species were 23. The major species were Plutella xylostella L., Prodenia litura (Fabricius) , Pieris rapae (Linnaeus), Myxus persicae (Sulzer) , and Bemisia tabaci (Gennadius). There neutral insects 4 species were colleted, most of them were Collembola2. From the dynamics of predators occurred in the different control strategies in the field, the predation efficiency were showed that: the number of predators in natural control > the number of predators in bio- pesticides control > the number of predators in chemical pesticides control. But their constructs are similar. Those indicated that the antipersonnel role of chemical pesticides is greater than bio-pesticides. According to the dynamics of number of predators on the earth's surface, it was indicated that the neutral insects may be play important role to the setting of predators in the former of cauliflower.3. According to the predators' functional responses in laboratory, when the temperature was rising, the number of prey eaten by predator increased. The numbers of M. persicae and B. tabaci consumed by predators were M. sexmaculatus > P. japonica >C. octomaculatum, while for P. xylostella consumed was L. pseudoannulata>P. procurva.4. The results evaluated by a model (Liu, et al. 2002) showed that the control efficiency of predators to whitefly were C. octomaculatum > P. japonica >M. sexmaculatus; and for M. persicae was P. japonica >M. sexmaculatus. P. xylostella consumed was L. pseudoannulata > P. procurva. The predation in natural control strategy was higher than the others two control strageties in the field.