The Study Of Relationships Between Farmland Landscape Structure And Predatory Natural Enemy Ladybugs Population

Population dynamics of two predatory beetles, Propylaea japonica and Harmonia axyridis were surveyed in agricultural landscapes composed of cotton and maize in North China.Results show that agricultural landscapes composition or crop type (cotton and maize) significantly effect population densities of two predatory beetles, P. japonica and H. axyridis in agricultural landscapes systerm. Population densities of two predatory beetles, P. japonica and H. axyridis on maize patches were higher than those on cotton patches, and adults of two predatory beetles prefer to inhabit maize plants. The population density of two predatory beetles varied on time scales on cotton patches, more adults of P. japonica in earlier and middle stage while less in later stage, less adults of H. axyridis in earlier and middle stage while more in later stage. Results suggested that maize can serve as a habitat or refuge sources for the predatory beetle and benefits predators to provide potential to enhance biological control for insect pests in cotton. Area proportions of maize patches in agricultural landscapes systerm significantly effect adult densities of two predatory beetles, P. japonica and H. axyridis. Results suggest that habitat management with a suitable proportion and spatial arrangement of cotton and maize may be an alternative planting pattern to enhance biological control for insect pest. In addition, we also found that the population quantity of ladybug on differences predators from poplar had significant impact in farmland-poplar landscape systems. Poplar border area ratio for the impact of P. japonica scale were100m,250m and1500m, in a certain proportion, with the increase in poplar, the number of farmland ladybug population decline, but most of the distance, the Poplar area the proportion of5%-20%, the largest number of habitats P. japonica populations, as a result, best yet would be the function of biological control against. In order to understand the factors influencing the ladybug species number of natural enemiesone in one step closer, we chose20counties in shandong province to analysis. We found that the proportion of farmland and unused in landscap also exist the lady beetle populations.