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

Methods: The irrigation and drainage ditches with high density of 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%) ( < 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 ( > 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.