Studies On Predation Function Systems Of The Dominant Predatory Natural Enemies For Diamondback Moth And Mechanism Of Enhancing Their Functions

This paper studied the species of predatory natural enemies of diamondback moth (DBM),Plutella xylosetella, the predation equivalency system, the predation function respones and their effect factors of the dominant predatory natural enemies of DBM, and the life table of experimental populations of 黫s axyridis(P). The main results as follows: 1. There are 50 species of predatory natural enemies of DBM in vegetable fields in Yangzhou district. They belonged to 7 Orders and 20 Families. The main predators of DBM were spiders, ladybirds, carabid beetles,earwirs ,and the dominant species were Leis axyridis and Lycosa pseudoannulata. 2. The amounts of predation of the main predators were determined respectly. The adjusted predation equivalency coefficients of different predators were calculated based on the amount of potential predation of each species. Thus, the predation equivalency systems were established. The multiple梥pecies of predators thresholds for controlling DBM were proposed for the predators in 48h: at the rosulate stage of cabbage, when the quivalency natural enemy梡est ratio surpassed I 8.8, DBM needn抰 to control. When the quivalency natural enemy梡est ratio ratio were 1: 3.8?l :17.7, DBM needn抰 to control, but need to monitor. When the quivalency natural enemy梡est ratio ratio was less than 1: 8.8,DBM need to control immediately. 3. The predation functional respones of the roles of the predators of DBM could be described by Holling II equation at the same condition. The effect of temperature, space, age, and species of the prey and so on to the functional respones of the female adults of Leis axyridis and Lycosa pseudoannulata were also studied. Temperature effected the rates of successful attack a and the handling time Th of the predators of DBM. At 15 C ?0X2 ,the a of the female adult of Leis axyridis increased,the Th shorted with temperature rising.The a decreased and the Th prolonged at 35 C. At 15 C?5C, the a of the female adult of Lycosapseudoannulata increased, the Th shorted with temperature rising.The a decreased and the Th prolonged with temperature rising at 25C---35C. The space size affected the rates of successful attack a and the handling time Th of predators of DBM. At all test spaces,the a of the female adults of Leis axyridis and Lycosapseudoannulata increased and the Th prolonged with space size extending. Prey梐ge affected also the rates of successful attack a and the handling time Th of predators of DBM. When the felame adult of Lets axyridis predated the second instar larvae of DBM, its a was higher. When it predated the third or the fourth instar larvae of DBM, its a was lower. When the felame adult of Lycosa pseudoannulata predated the second or the third instar larvae of DBM, its a was higher. When it predated the fourth instar larvae of DBM, its a was lower. As the DBM larvae instar increasing two predators?Th prolonged. 4. Species of prey affected predation actions of predators 3f DBM. In the coexistence of the vegetable aphid and DBM, Lycosa pseudoannulata more preferable to DBM than Leis axyridis. And the predation functional repones of the two predators belonged still to the type of Holling II. Field experiment showed that the predation functions of the predators to DBM didn抰 change when the small amount of aphid exsited. 5. The intraspecific interference of female adult of Lycosa pseudoannulata> that of female adult Leis axyridis >interference between this two predators. At the same time,the intraspec...