Control of the Invasive Agricultural Pest Pomacea canaliculata with a Novel Molluscicide: Efficacy and Safety to Nontarget Species.

The golden apple snail Pomacea canaliculata is an invasive pest that causes extensive damage to agricultural production. P. canaliculata is also an intermediate host of Angiostrongylus cantonensis, which causes human eosinophilic meningitis. In this study, the molluscicidal activity and safety profile of a novel molluscicide PBQ [1-(4-chlorophenyl)-3-(pyridin-3-yl)urea] were evaluated. PBQ exhibited strong molluscicidal potency against adult and juvenile snails (LC50 values of 0.39 and 0.07 mg/L, respectively). In field trials, PBQ killed 99.42% of the snails at 0.25 g a.i./m2. An acute toxicity test in rats demonstrated that PBQ is a generally nonhazardous chemical. PBQ is also generally safe for nontarget organisms including Brachydanio rerio, Daphnia magna, and Apis mellifera L. Transcriptomics analysis revealed that PBQ had a significant impact on the carbohydrate and lipid metabolism pathways, which provided insights into its molluscicidal mechanism. These results suggest that PBQ could be developed as an effective and safe molluscicide for P. canaliculata control.

Spatiotemporal variability in salinity and hydraulic relationship with salt intrusion in the tidal reaches of the Minjiang River, Fujian Province, China.

Salinity is one of the most important factors for tidal-affected water bodies including estuaries and tidal river reaches. However, due to the limitations of simultaneous manual monitoring in long-distance areas, studies of estuaries are preferred to tidal reaches. Hence, in this study, we investigated the tidal reach of the Minjiang River and five sets of field observations were used to determine the influence of saltwater intrusion in different seasons. During the dry and wet season with low discharge, the longitudinal salinity profiles showed that a station located about 45 km from the river mouth still suffered from saltwater intrusion especially when the upstream discharge was under 754 m3 s-1, where the periodical fluctuation in the salinity remained the same with the water level, but there was a time lag of approximately 4 h compared with the discharge process. However, during the wet season in April and May 2016, the monitored salinity was approximately at the detectable limit of 0.02-0.04 ppt at the station close to the river mouth, which indicated that there was no saltwater exchange into the river, although dual flow directions were observed in the survey periods. The major differences among five survey periods were mainly related to upstream discharge rather than the seasons, the tidal range, and tidal excursion. The conclusions of this study have strategic importance for protecting water sources by guiding the government to assess the optimal freshwater release time and discharge rate to prevent saltwater entering the important tidal-affected river reaches.

[Effect of comprehensive schistosomiasis control measures based on infection source control in mountainous areas of Yunnan Province].

OBJECTIVE: To evaluate the effect of comprehensive schistosomiasis control measures based on infection source control in plateau mountain areas of Yunnan Province. METHODS: From 2006 to 2004, four administrative villages were selected as test areas from plateau canyon and plateau basin endemic areas in Jindun Town, Heqing County, two villages each type, and the comprehensive control measures were implemented, including the examination and treatment of schistosomiasis, Oncomelania hupensis snail survey and control, health education, improving drinking water and lavatories, banning grazing, constructing sanitary pen of livestock, replacing cattle with machine, etc. The schistosome infection state and snail status in 2006 were treated as the baseline information, and the effect of the comprehensive measures were evaluated. Results The infection rate of human in plateau canyon areas decreased from 4.94% in 2006 to 0.06% in 2014, and that of livestock decreased from 1.11% to 0. In plateau basin areas, there was only 1 case of schistosomiasis found in Xiaolian Village in 2007, and no any other cases found in the other years, the infection rates of livestock dropped from 7.38% to 0. Compared with 2006, the snail areas in the two type areas decreased by 74.89% and 75.30%, respectively, meanwhile, the percentage of snail area, the occurrence rate of frames with snails, as well as the average density of living snails also decreased, and no infected snails were found since 2008. Xidian and Xinzhuang villages in plateau canyon area reached the criteria of schistosomiasis transmission controlled in 2009, and Xiao-lian and Kangfu villages in plateau basin reached the criteria of transmission interrupted in 2014. CONCLUSIONS: The comprehensive schistosomiasis control measures based on infection source control can effectively control the endemic situation of schistosomiasis in plateau areas of Yunnan Province. In the future, we should pay an equal attention to the infection sources control and snail control to consolidate and amplify the achievement of schistosomiasis control.

[Molluscicidal effect of WPN and MNSC on Lymnaea].

OBJECTIVE: To evaluate the molluscicidal effect of wettable powder of 50% niclosamide ethanolamide salt (WPN) and suspension concentrate of 26% metaldehyde and niclosamide (MNSC) on Lymnaea. METHODS: WPN and MNSC were prepared as a series of solutions containing the active ingredient concentrations of 0.06, 0.13, 0.25, 0.50, 1.00, 2.00 mg/L and 4.00 mg/L, and the adult Lymnaea snails were soaked in the above mentioned series of solutions in the laboratory, and the LC50 values were calculated. The doses of active ingredient concentrations of 0.03, 0.06, 0.13, 0.25, 0.50, 1.00 g/m2 and 2.00 g/m2 of WPN and MNSC were adopted to spray on Lymnaea snails in the laboratory, and the LC50 values were calculated. A series of solutions containing the active ingredient concentrations of 1.00 mg/L, 0.50 mg/L, 0.25 mg/L, and 0.13 mg/L of WPN and MNSC were prepared, and the adult Lymnaea snails were put into the bowls with each concentration solution above mentioned and the climbing situation of the snails was observed at different time. RESULTS: By the immersion method, LC50 values of WPN at 48 h and 72 h were 0.93 mg/L and 0.64 mg/L respectively; LC50 values of MNSC at 48 h and 72 h were 0.74 mg/L and 0.51 mg/L respectively; by the spray method, when active ingredient concentrations of WPN and MNSC were 1.00 g/m2 or more, the death rates were both 100% after 3 days. In the climbing test, the Lymnaea snails did not climb in the solutions containing the active ingredient concentration of 1.00 mg/L of WPN and MNSC, however, a few snails climbed in the low concentrations. CONCLUSIONS: WPN and MNSC both have the effect of killing Lymnaea snails and inhibiting their climbing. By using the immersion method in the field, the active ingredient concentration of 2.00 mg/L of WPN and MNSC for 48 h is appropriate; by using the spray method, the active ingredient content of 1.00 g/m2 of WPN and MNSC for 3 days is appropriate.

[Effect of comprehensive control and management of schistosomiasis at plateaus regions in Yunnan Province].

OBJECTIVE: To evaluate the effect of comprehensive control and management of schistosomiasis at plateaus regions in Yunnan Province. METHODS: Xiaolian and Kangfu villages at plateaus regions where schistosomiasis was endemic were selected as study areas from 2006 to 2011, the schistosomiasis comprehensive control measures were conducted, and these measures included the health education, chemotherapy, stool and water management, grazing forbidden, Oncomelania snail control, etc. combined with the infrastructure of farmland water conservancy, agricultural comprehensive development, adjustment of industry structure, returning farmland to forest, ditch hardening, and aquaculture. RESULTS: At Xiaolian Village, no schistosomiasis patient and livestock were found from 2008; and at Kangfu Village, no schistosomiasis patient was detected from 2006 and no schistosomiasis domestic animal was found from 2008. In 2011, the snail area, percent of frames with living snails, the number of snails, average concentration of living snails, and the highest concentration of living snails descended by 69.99%, 81.86%, 88.86%, 89.71%, 57.95% at Xiaolian Village, and descended by 27.65%, 1.11%, 94.71%, 92.16%, 88.00% at Kangfu Village, respectively, compared with those in 2006. The ratios of infected snail area to snail area were 68.91% in 2006 and 69.13% in 2007 at Xiaolian Village, and 61.73% in 2006 and 43.24% in 2007 at Kangfu Village. There were no infected snails from 2008 in the two villages. CONCLUSION: The comprehensive control and management measures can effectively control the schistosomiasis prevalence at plateaus regions.