Population Dynamic Of Small Brown Planthopper (SBPH), Laodelphax Striatellus In Different Habitats And Host Suitability Of SBPH

Rice stripe disease, caused by Rice stripe virus (RSV), led to severe or even crippling losses in JiangHuai rice region in recent years. As the most important vector of RSV, the small brown planthopper (SBPH) (Laodelphax striatellus) is largely responsible for the epidemic phase of the disease. In order to clarify the occurrence regularity and host adaptation of SBPH, the population dynamic of SBPH in different habitats, the fitness of SBPH on different plants and the effect of detoxifying enzymes and target enzymes on host adaptation of SBPH were studied in this paper. The main results were as followings:1. The population dynamic of SBPH in different habitats was investigated. The results showed that SBPH occurred six generations a year and overwintered mainly on wheat and weeds in Fuyang county, Zhejiang province. The overwintering generation adults emerged from late February to middle April. The first generation nymphs hatched from middle April to early May, and mainly damaged wheat. The second generation nymph occurred from late May to late June and mainly infested the early rice and Mid-rice. The peak of this generation appeared in the middle June. The third generation occurred from early July to early August, mainly infested Mid-rice, direct seeding late rice and the Gramineous weeds of idle field(e.g. Echinochloa crusgalli of wild land). The fourth generation occurred from early August to early September, mainly damaged late rice, and a few pests were observed on weeds. The fifth generation occurred in early September, mainly distributed in Mid-rice, late rice, idle field and weeds land. The fastigium of the third, fourth and fifth generation took place in middle July, early August and mid September respectively. The fifth generation adults in the paddy field immigrated to the wheat yard and weeds, but the adult in the weeds yard did not immigrate and went on developing. The adult of SBPH could immigrate three times in whole year. The number of SBPH was 14.9 to 22.7 individuals/10m~2 in wheat yield and 6.6～55 individuals/10m~2 in rice yield respectively in 2006～2007. The average quantity of SBPH in Fuyang was lower than that in the heavy disaster areas of rice stripe disease.2. The development and reproduction of SBPH on 57 different plants including Oryza sativa, Zea mays, Sorghum vulgare and E. crusgalli etc were studied by caging method in laboratory. The results indicated that nymphal development duration, emergence rate, adult weight, adult longevity and fecundity of SBPH on different plants were significantly different. According to principal component analysis and population trend index analysis, five plants (E. crusgalli etc.) were the most suitable host plants, with the emergence rates of SBPH on these plants ranging from 59.4% to 86.9%, and the population trend indexes above 27.8. Nine plants (Lolium perenne etc.) were also suitable for the small brown planthopper, 27.0% - 64.5% individuals on those plants can emerge, and the population trend indexes were above 10. Five plants such as Eleusine indica were scarcely suitable for the survival of SBPH, 13.0% - 35.6% emergence rates were observed, and population trend index were 1-10. Thirteen plants (Bromus inermi etc.) were unfit for SBPH's survival, less than 10% individuals on them can emerge, and the population increase could not reach 1. Nymphs of SBPH on the other twenty-five plants such as Zea mays could not emerge. Lolium maloiforam, Beckmannia syzigachne, Polypogon fugax, Poa acroleuca, Avena fatua and Capsella bursapastoris were the newly confirmed host plants.3. The activity of detoxifying enzymes and target enzymes in SBPH, compared with BPH, which fed on E. crusgalli but firstly on rice, were measured to study the effect of those enzymes on the host adaptation of the pest. The results indicated that the activities of detoxifying enzymes in SBPH were significantly different from those in BPH. Theα-NA esterase activity in SBPH was significantly higher than that in BPH, and there were more SBPH individuals having highα-NA esterase activity. Theβ-NA esterase activity in male of SBPH and glutathione S-transferase activity in female of SBPH were apparently higher than those in BPH, but the distribution of the enzyme activity in both planthoppers seriously overlapped. Few differences were observed in acetylcholinesterase activity testing. The results indicated that carbaxylesterase especiallyα-NA esterase played an important role in host adapting in SBPH.