Study On Resources Of Natural Enemy Insects And Occurrence Of The Main Species In Shaannxi Apple Orchard

One of important fruits is apple in people's life at the present. With the suitable special eco-condition of growing up, Loess Plateau is one of the ecological prepotent areas for apple planting in seven regions of the world. In Shaanxi province, being included in Loess Plateau, the apple is one of the four special industries.But, because of the remains of pesticides, the growing of investment cost and the effect of poor exterior quality, the international markets are limited. The worst affect of them is caused by the remains of pesticides after a large pesticides are applied to control diseases and pests. The best methods of the management of apple diseases and pests are systematic control ways and the use of the natural enemy resources. The application of natural enemies is one of the best ways. In Shaanxi natural, the resource of natural enemy of pests is abundant, and be played an important role in controlling pests. The structure of natural enemy community had obvious changed after the changes of ecological environment in apple orchards, because of the viewly ecological systems that are made by distribution of apple planted was well changed, expanded incessantly, and transforming of producing techniques, as grafting to change apple breed, adjusting branch's shape and grassing in orchards. But natural enemies were not studied simultaneously, and mankind had many diffcution to apply them. So they were studied indoors and outdoors in this thesis to find out the changes and superiority of natural enemy insect resources of apple orchards after planting systems had been transformed in Shaanxi. This thesis want to promote the application of natural enemy insects and push development of pest biological control.They were systemally studied in apple orchards .The results showed that:1.Resources of natural enemy insects in apple orchards are various in Shaanxi province,.56 species of natural enemy insects, which belong to 8 ordo 22 faimiliar and include 19 species of ladybirds, 13 speces of aphid lions, 4 species of braconds, 9 species of insect-phagous bugs and 11 species of the other natural enemies are collected. Ladybirds, aphid lions and braconds are main kinds of them.2. The altitude of apple orchards influence the distribution of natural enemy insects.They are different after the apple orchards in different altitude. It is a tendency of decrease to the population and number distribution of them when the altitude is increased. They are the most in the apple orchards at north of QinLing mountain and south of WeiHe river.3. The spatial distributions of natural enemy insects have different in the apple tree. The number distribution of them was nearly different from all directions (east, south, west and north) and outer and inter canopy of apple trees. But they are more in middle and below canopy than in above canopy.4. The predatory function of two species of aphid lions to Aphis citricola Van der Goot are separately conformed to maths models. The predatory functions of the adults and 4th-instar larva of Hippodamia (Adonia) variegata (Goeze) and the adults of Coccinella septempunctata Linnaeus to Aphis citricola Van der Goot in apple trees were tested indoors. The results showed that the Holling- ii equations could describe the functional responses of the adults and 4th-instar larva of Hippodamia (Adonia) variegata (Goeze) and the adults of Coccinella septempunctata Linnaeus to the density of Aphis citricola Van der Goot. The predatory number of the adults and 4th-instar larva of Hippodamia (Adonia) variegata (Goeze) and the adults of Coccinella septempunctata Linnaeus to Aphis citricola Van der Goot decrease when themselves density is increased, and themselves have interference function. The maths Model of Hassell could reflect their functional responses.5. The development occurrence of natural enemy insects was obtained in apple orchards at Luochuan. Hippodamia variegate (Goeze) and Chrysopa septempunctata Wesmael, which are two of the dominant ones of natural enemy insects in apple orchards at Luochuan, almostly are in the state of hibernation at November to March the next year. They begin to act at April. They are the most at June to September in the orchards. The number of Hippodamia variegate (Goeze) increased gradually from March to July, it is the most at July. Two population peaks of Chrysopa septempunctata Wesmael were discovered at May and July to August.