Effect Of Agricultural Measures On Brown Planthopper Occurrence And Their Mechanisms

Brown planthopper (BPH), Nilaparvata lugens (Stal) is a major pest of rice in China. Resistance of rice varieties is widely considered as one of the best way to prevent and control BPH in its integrated management. Fertilization, an important agricultural measure, can indirectly affect the pest occurrence through affecting plant growth potential. In this paper, effects of different planting methods, rice varieties, nitrogen fertilizer application rate on occurrence rules of BPH and their mechanisms were studied. The results were summarized as follows:1. Numbers of BPH were significantly different among three different plant methods. On September10and September20, numbers of BPH in hand planting rice were1540.95±12.73and8259.00±983.03millions/hm2respectively, while those in the direct-seeding and machine-transplanted rice were420.30±115.61and242.25±70.23millions/hm2,84.30±9.70and49.20±6.15millions/hm2respectively. Number of BPH in hand planting rice was the highest, and that in machine-transplanted rice was the lowest. The numbers of natural enemies (mainly refers to the spiders and Cyrtorhinus lividipennis) in different planting patterns rice were also different. The number of spiders in machine-transplanted rice was the highest, and that in direct-seeding rice was the lowest. The number of C. lividipennis in hand planting rice was significantly higher than the others.2. Numbers of BPH in TNI were significantly higher than those in Huaidao9, Zhejing22, Ningjing1and Bing123. Transplanting densities (High density:20cm×13cm; Low density:25cm×13cm) had an obvious but instable effect on BPH’s occurrence, and sometimes rice varieties and transplanting densities had an interaction on the occurrence of BPH. Numbers of spiders in different rice varieties (including wolf/jumping spider, cobweb weaver, elongated orb-weaver, micro spider) were different. It showed that the numbers of spiders in TN1were significantly higher than those in other4rice varieties. However, there’s no significant differentce in the number of C. lividipennis. The content of chlorophyll and soluble sugar in rice leaves of different rice varieties were obviously different in three growth stages, including tillering stage, jointing-booting stage and grain-filling stage. The order of chlorophyll content in rice leaves in tillering stage is Zhejing22> Huaidao9>Ningjingl>Bing123>TN1. The content of soluble protein in rice leaves of different rice varieties was also different in jointing-booting and grain-filling stage. The numbers of wolf/jumping spider and elongated orb-weaver in low density rice sometimes were significantly higher than those in high density rice. However, transplanting densities had an instable effect on the number of cobweb weaver. The number of micro spiders was similar in different transplanting densities rice. Transplanting densities had no significant effect on the numbers of C. lividipennis. However, obvious differences cause by transplanting densities occurred in chlorophyll, soluble sugar and soluble protein content in rice leaves.3. Numbers of BPH in TN1were significantly higher than that in Zhejing22, Bing123, Ningjing1and Huaidao9. Nitrogen fertilizer application rates (0,125kg/hm2,250kg/hm2)also had a significant effect on the occurrence of BPH. It showed that the number of BPH in high nitrogen level treated rice was higher than that on low nitrogen level. In addition, rice varieties and nitrogen fertilizer application rates had a significant interaction in BPH occurrence. The numbers of spiders (including wolf spider, cobweb weaver, elongated orb-weaver, micro spider) and C. lividipennis in TN1were significantly higher than those in the other4rice varieties. The content of chlorophyll, soluble protein and soluble sugar in leaves of different rice varieties were obviously different in three growth stages (tillering stage, jointing-booting stage and grain-filling stage). Oxalic acid content of different rice varieties in tillering stage was lower than those in jointing-booting and grain-filling stage. In tillering stage and jointing-booting stage, flavonoids content in TN1was significantly higher than those in Zhejing22, Bing123, Ningjing1and Huaidao9. There’s no significant difference among the amount of free amino acids in BPH-body feeding on different rice varieties. The numbers of C. lividipennis and cobweb weaver in high nitrogen level treated rice were significantly higher than those in no nitrogen treated rice (the control). The numbers of wolf/jumping spider, elongated orb-weaver, micro spiders in high and low nitrogen levels rice were higher than those in the control. In jointing-booting and grain-filling stage, the content of chlorophyll in high nitrogen level treated rice was higher than that in low nitrogen level rice. In tillering, jointing-booting and grain-filling stage, soluble protein content in high nitrogen level rice was higher than that in low nitrogen level rice. Nitrogen fertilizer application rate had an instable effect on soluble sugar content of rice. In tillering stage, oxalic acid content in high nitrogen level rice was lower than that in low nitrogen level rice and contrast rice. In grain-filling stage, oxalic acid content in the control was higher than that in low nitrogen level rice, and that in high nitrogen level rice was the lowest. In tillering and grain-filling stage, flavonoids content in high nitrogen level treated rice was the lowest, and that in the control was the highest. The contents of5free amino acids, Gly, Val, He, Leu and Lys in BPH-body feeding on high nitrogen level treated rice were significantly higher than those in the control.