[Spatial and temporal characteristics of distribution of Oncomelania hupensis in Eryuan County from 2005 to 2012].

OBJECTIVE: To study the spatial and temporal characteristics of Oncomelania hupensis in Eryuan County, Yunnan Province from 2005 to 2012, so as to provide the scientific evidence for snail surveillance and control. METHODS: Based on the geographic database of O. hupensis snail distribution from 2005 to 2012, the spatial and local autocorrelation analysis and "hot spots" analysis were applied to analyze the spatial and temporal characteristics of the snails. RESULTS: Percent of frames with O. hupensis snails in Eryuan County decreased as a whole from 2005 to 2012. The spatial clustering of global autocorrelation (Moran's I) was increasing from 2007 to 2012 and all Moran's I values showed statistically significance. The local spatial autocorrelation analysis indicated that the number of villages of High-High type of correlation model increased from 2 in 2005 to 7 in 2012, which mainly clustered in plateau canyon areas. The infected snails with High-High type mainly distributed in plateau basin region in 2007. Further "hot spot" analysis found that the living snails gathered in Xinzhuang, Liantie, Xipo and Taiping nearby areas. CONCLUSIONS: The snail distribution in Eryuan has global and local spatial autocorrelations. The number of villages of High-High type of correlation increased. These findings provide the basis for target control of O.hupensis in the future.

[Short - term effects of two kinds of plastic mulch on Oncomelania hupensis snail control in irrigation and drainage ditches in Yunnan Province].

OBJECTIVE: To evaluate and compare the short-term effects of two kinds of plastic mulch on Oncomelania hupensis snail control in irrigation and drainage ditches with snails in Yunnan Province. METHODS: The irrigation and drainage ditches with high density of Oncomelania hupensis snails were chosen as the investigation sites, and then 4 groups were set, namely a colorless plastic mulch group, black plastic mulch group, colorless plastic mulch with molluscicide group and black plastic mulch with molluscicide group. The snail situation of the 4 groups was surveyed before the experiment and 7, 14, 21, 30 days after covering plastic mulch, and the snail death rates were compared among the 4 groups. Meanwhile, the hourly temperatures of soil surface, soil surface under plastic mulch and soil layer 5, 15 cm under the surface as well as the weather situation during the study period were measured and recorded. RESULTS: The average snail mortality rate of the colorless plastic mulch group was only 15.29% that was higher than that of the black plastic mulch group (6.56%) (P < 0.01). The average snail mortality rates of the colorless and black plastic mulch with molluscicide groups were 40.80% and 50.15%, respectively, and there was no statistic difference between them (P > 0.05). Both kinds of plastic mulches could raise the temperature of the soil surface under plastic mulch and the soil layer below it, and the temperature of soil under the mulches increased over the cover time, and the average temperature of the soil surface under the black mulch in 30 days was higher than that under the colorless mulch. CONCLUSIONS: It is not suitable to use plastic mulch only in irrigation and drainage ditches with snails widely in Yunnan Province because of its low effect, and if necessary, the molluscicide should be added.