Studies On The Effect That Planting Grass And Releasing Natural Enemies Has The Pests Under Control In The Orchard

This paper studied the variety and amount of the arthropod in grass-planting orchard and no-grass orchard releasing Amblyseius fallacies in clover-planting orchard, and the control effect of pests .The main contents and conclusions are as follows:Under the control of the ecosystem in the orchard, the natural factors were very important to the occurrence and damage of the pests. The comprehensive effect of natural enemies and plant resistance went beyond 80%(pimonte 1992). After planting grass in the orchard, the natural enemies enjoyed a good living environment. Diversity, richness, evenness of community were all higher than that in no-grass orchard and it can enhanced the stability of ecosystem, so it was easy to keep ecological balance in grass-planting orchard.By investigation, there were a great number of natural enemies in the grass-planting orchard such as Aranea, Coccinella septempunctata, Scolothrips sexmaculatus and etc. It was very obvious that the variety and density of natural enemies in the grass-planting orchard was more than that in the no-grass orchard. Conversely the amount of pests decreased greatly.There were a great number of natural enemies in the wheat field. Before the wheat harvest, they began to transfer to the orchard, So protecting natural enemies in nearby wheat field was a feasible measure to increase natural enemies in the orchard.Applying agriculture chemical was the main reason that the pests were rampant again. The natural balance was destroyed after applying agriculture chemical, the amount of pests decreased rapidly if the natural environment was fit, while the amount of natural enemies was difficult to return to normal.By investigation on occurrence time of local natural enemies and pests in the clover-planting orchard, the local natural enemies couldn't be in complete control of the pests, so the research on releasing suitable natural enemies was very necessary.Release was made in the apple orchard in Qingdao city, Shandong province. Amblyseius fallacies could survive, develop, and give a good control of pest mite Panonychus ulmi. The number of the pest mitewas 22.45 female adult/leaf on release trees, while 55.52/leaf on check tree in mid-July, the peak time of abundance.Several kinds of predatory natural enemies built up in released plot and check plot free from chemical spraying. Among which, Stethorus punctillum was dominant species, it played an significant role in the late season's spider mite control, especially on the check tree. Very few natural enemies were found in the chemical control orchard.The OP resistance in the A. fallacies strain studied had declined due to the long laboratory rearing. Therefore, insecticide spraying was the major factor affecting the population growth of A. fallacies.Some other problems regarding the potential of utilizing the predator in apple orchards in Shandong area were discussed.