[Natural increase of parasitoids population of diamondback moth Plutella xylostella under ecological control condition].

The parasitoids of diamondback moth Plutella xylostella was unfolded year after year since a series of ecological measurement was taken in Shenzhen Longgang Demonstrate Ecological Farm. The parasitical eggs of diamondback moth by Trichogrammatoidea bactraz and Trichogramma ostrinae were firstly found in the field in September 1999. Another two parasitoids, Trichogramma confusum and Trichogramma bilingensis also had a certain parasitism in nature. Now, the four Trichogramma species had already established their natural population, and their average parasitism was 15% around the year, and reached 25-30% at the harvesting period in Autumn, among them, Trichogramma confusum was predominant in quantity, which showed that ecological control played an important role in augmenting and protecting the population of Trichogramma in nature.