Preliminary Analysis On The Relationship Between Planthopper Dynamics And Landscape Pattern

Rice planthoppers are one of the most important pests on rice production in Asia. They can do harm to rice not only through piercing-sucking the sap but also can spread a variety of viruses, and cause rice virus diseases. In recent years, affected by climate, cultivation, crop varieties, inappropriate control methods and so on, the planthoppers had frequent outbreaks. In order to get effective management measures on the planthoppers, a large number of scholars study on it from different perspectives. This study mainly did research from the aspects of landscape ecology, and also use secondary methods in molecular biology to explore the characteristics of their occurrence. The main research results were as follows:1. From2011to2012, we did research on planthoppers in the experiment farm of Zhejiang University and surroundings by the sweep net, ocular estimation and plate-tapping. Together with light trapping and ovary dissection of the small brown planthopper (SBPH), we investigated the population dynamics of the small brown planthoppers, the relationship between its occurrence and several variables of mainly vegetation landscape. We found that there is very great variation between different years of the occurrence quantity of the small brown planthoppers population. In June,2011, there was a large immigration peak, and consequently resulted in a peak of nymph in middle June. In2012, the situation of immigration and occurrence of SBPH was lighter than that in2011. The green bristle grass (Setaira viridis (L.) Beauv) beside cornfield, corns and other vegetation are thought to be the main place for adult and nymph of SBPH, shows that it could form breeding population at these habitats, and become the source of small brown planthoppers for rice sowed in the late June. Besides, on different time, at special vegetation it was significant differences, and it likes corn more than rice. 2. In2012, we monitored the population dynamics of the white-backed planthopper (WBPH) and the brown planthopper (BPH) in farm of Zhejiang University and surroundings by the sweep net, ocular estimation and plate-tapping. Together with light trapping, we investigated the dynamics of the planthoppers and the relationship between their occurrences and the main vegetation diversity variables. The results showed that the occurrence of the white-backed planthopper in2012was obviously higher than in2011. In the whole year the brown planthopper has the characteristics of "rapidly increasing and decreasing, multi peaks"The main habitats of the white-backed planthopper and the brown planthopper was rice field, but WBPH was also monitored in corn, grass weeds and other vegetations and it could form breeding population at these places.3. Through simulating rice field on agriculture landscape by setting sentinel rice seedlings in different habitats and the population dynamics monitored showed that the occurrence of planthopper was closely correlated with the agriculture landscape pattern. On different landscape patterns, the number of planthopper is different. A equation was established for the area under the curve of BPH population dynamics in the sentinel rice plants against the habitat biodiversity index, showed that the occurrence quantity of BPH had close relation with richness, diversity, uniformity of vegetation etc., the more complex of landscape structure and diversity of vegetation type, the less the occurrence of BPH. This suggests that we can arrange agricultural structure such as separating different kinds of crops by planting different weeds in order to increase the complexity of farmland ecosystem and to reduce crop yield by pests.