ABSTRACT
Objective To evaluate the effect of Oncomelania hupensis snail control of cutting the beach group in the south of Shaobo Lake. Methods The general situation of the project of cutting the beach was surveyed, and the snail distribution was surveyed and the results were compared before and after cutting the beach in the beach group. Results The area of cutting beach was 928.33 hm2, the cubic meter of earthwork was 1 717.00 m3, the area of dumping ground was 425.76 hm2, the beach surface elevation was 3.2 m after cutting the beach, and the beach surface was fallen to 1.0 m under the ordinary water level. The area with snails was 44.69 hm2 before cutting the beach in 2011 but the area with snails was 1.78 hm2 after cutting the beach in 2018. The area with remaining snails was declined by 96.02% in 2018 as compared with that in 2011, and surviving snails were distributed on the uncut beach face. Conclusion In Shaobo Lake, the O. hupensis snail breeding environment is eliminated by raising or lowering the beach, so it is an effective measure of snail control in lake regions.
ABSTRACT
Objective To evaluate the effect of Oncomelania hupensis snail control of cutting the beach group in the south of Shaobo Lake. Methods The general situation of the project of cutting the beach was surveyed, and the snail distribution was surveyed and the results were compared before and after cutting the beach in the beach group. Results The area of cutting beach was 928.33 hm2, the cubic meter of earthwork was 1 717.00 m3, the area of dumping ground was 425.76 hm2, the beach surface elevation was 3.2 m after cutting the beach, and the beach surface was fallen to 1.0 m under the ordinary water level. The area with snails was 44.69 hm2 before cutting the beach in 2011 but the area with snails was 1.78 hm2 after cutting the beach in 2018. The area with remaining snails was declined by 96.02% in 2018 as compared with that in 2011, and surviving snails were distributed on the uncut beach face. Conclusion In Shaobo Lake, the O. hupensis snail breeding environment is eliminated by raising or lowering the beach, so it is an effective measure of snail control in lake regions.
ABSTRACT
Objective To evaluate the effect and cost-effectiveness of three commonly used molluscicides, 4% "Luo-wei" (tea-seed distilled saponins, TDS), 50% niclosamide ethanolamine salt wettable powder (NESWP), and 26% metaldehyde and niclosamide suspension concentrate (MNSC) in large-scale field application, so as to provide the references for formulating the strategy of snail control. Methods The field test and parallel comparison were implemented. A marshland with Oncomelania hupensis snails of the Yangtze River was divided into 4 parts (10 hm2) for the research, and three of them were experimental areas while the last one was a blank control area. The experimental areas were sprayed with 4% "Luo-wei", 50% NESWP and 26% MNSC respectively for 3 times and the interval was 1 week. Seven days after each spraying the effect of snail control was investigated, and the costs of molluscicides, labor, transportation, fuel consumption and mechanical loss were recorded. The cost of each molluscicide, snail mortality, snail density, and the cost of increasing 1% of snail mortality per 100 m2 were analyzed and compared. Results After the first, second and third spraying, the corrected snail mortality rates were 67.34%, 76.55% and 84.60% respectively in the 4% "Luo-wei" group; the corrected snail mortality rates were 64.71%, 75.17% and 83.89% respectively in the 50% NESWP group; the corrected snail mortality rates were 66.55%, 76.27% and 86.67% respectively in the 26% MNSC group. There was no significant difference among the 3 groups in the snail mortality at the same spraying time (χ2 = 1.590, 0.571, 3.238, all P > 0.05) . In addition, along with the increase of the spraying times, the snail mortality of each group was increased significantly compared to that of the control group (χ2 = 79.333, 94.718, 117.020, all P < 0.01) . After the first, second and third spraying, the reduction rates of snail density were 69.82%–86.60% in the 4% "Luo-wei" group, 68.66%–86.55% in the 50% NESWP group, and 71.89%–88.87% in the 26% MNSC group respectively. The decreasing amplitude of the snail density was more than 85% in all the experimental areas after 3 rounds of spraying molluscicide. The snail control costs per 100 hm2 were 19.57, 11.97 Yuan and 10.47 Yuan in the 4% "Luo-wei" group, 50% NESWP group, and 26% MNSC group respectively. After the first, second and third spraying, the costs of increasing 1% of snail mortality per 100 m2 were 0.30, 2.08 Yuan and 2.38 Yuan in the 4% "Luo-wei" group, 0.20, 1.10 Yuan and 1.32 Yuan in the 50% NESWP group, and 0.17, 1.04 Yuan and 0.97 Yuan in the 26% MNSC group respectively, and the cost-effectiveness was the highest at the first spraying in all the three groups. Conclusions The effects of the three molluscicides for snail control are similar, but the efficacy of snail control is reduced as the spraying time increases.
ABSTRACT
Objective To evaluate the effect and cost-effectiveness of three commonly used molluscicides, 4% "Luo-wei" (tea-seed distilled saponins, TDS), 50% niclosamide ethanolamine salt wettable powder (NESWP), and 26% metaldehyde and niclosamide suspension concentrate (MNSC) in large-scale field application, so as to provide the references for formulating the strategy of snail control. Methods The field test and parallel comparison were implemented. A marshland with Oncomelania hupensis snails of the Yangtze River was divided into 4 parts (10 hm2) for the research, and three of them were experimental areas while the last one was a blank control area. The experimental areas were sprayed with 4% "Luo-wei", 50% NESWP and 26% MNSC respectively for 3 times and the interval was 1 week. Seven days after each spraying the effect of snail control was investigated, and the costs of molluscicides, labor, transportation, fuel consumption and mechanical loss were recorded. The cost of each molluscicide, snail mortality, snail density, and the cost of increasing 1% of snail mortality per 100 m2 were analyzed and compared. Results After the first, second and third spraying, the corrected snail mortality rates were 67.34%, 76.55% and 84.60% respectively in the 4% "Luo-wei" group; the corrected snail mortality rates were 64.71%, 75.17% and 83.89% respectively in the 50% NESWP group; the corrected snail mortality rates were 66.55%, 76.27% and 86.67% respectively in the 26% MNSC group. There was no significant difference among the 3 groups in the snail mortality at the same spraying time (χ2 = 1.590, 0.571, 3.238, all P > 0.05) . In addition, along with the increase of the spraying times, the snail mortality of each group was increased significantly compared to that of the control group (χ2 = 79.333, 94.718, 117.020, all P < 0.01) . After the first, second and third spraying, the reduction rates of snail density were 69.82%–86.60% in the 4% "Luo-wei" group, 68.66%–86.55% in the 50% NESWP group, and 71.89%–88.87% in the 26% MNSC group respectively. The decreasing amplitude of the snail density was more than 85% in all the experimental areas after 3 rounds of spraying molluscicide. The snail control costs per 100 hm2 were 19.57, 11.97 Yuan and 10.47 Yuan in the 4% "Luo-wei" group, 50% NESWP group, and 26% MNSC group respectively. After the first, second and third spraying, the costs of increasing 1% of snail mortality per 100 m2 were 0.30, 2.08 Yuan and 2.38 Yuan in the 4% "Luo-wei" group, 0.20, 1.10 Yuan and 1.32 Yuan in the 50% NESWP group, and 0.17, 1.04 Yuan and 0.97 Yuan in the 26% MNSC group respectively, and the cost-effectiveness was the highest at the first spraying in all the three groups. Conclusions The effects of the three molluscicides for snail control are similar, but the efficacy of snail control is reduced as the spraying time increases.