[Molluscicidal effect of spraying 5% niclosamide ethanolamine salt granules with drones against Oncomelania hupensis in marshland areas].

Objective: To evaluate the molluscicidal effect of spraying 5% niclosamide ethanolamine salt granules with drones against of Oncomelania hupensis snails in snail habitats in marshland areas.

Methods: From September to October, 2022, marshlands were sampled from Dantu District, Zhenjiang City, Jiangsu Province as study areas, and assigned into four groups, of approximately 3 000 m² per group. In Group A, environmental cleaning was performed, followed by spraying 5% niclosamide ethanolamine salt granules with knapsack sprayers at a dose of 40 g/m², and in Group B, 5% niclosamide ethanolamine salt granules were sprayed with knapsack sprayers at a dose of 40 g/m² without environmental cleaning, while in Group C, environmental cleaning was conducted, followed by spraying 5% niclosamide ethanolamine salt granules with drones at a dose of 40 g/m², and in Group D, 5% niclosamide ethanolamine salt granules were sprayed with drones at a dose of 40 g/m² without environmental cleaning. Then, the study areas in each group were equally divided into six blocks, with Block 1 for baseline surveys and blocks 2 to 6 for snail surveys 1, 3, 5, 7, 14 days following chemical treatment. The mortality of snails and the reduction of the density of living snails were calculated.

Results: A total of 132 frames were surveyed during the period from September to October 2022, and the occurrence of frames with living snails and means density of living snails were 61.36% (81/132) and 1.58 snails/0.1 m², respectively. The overall mortality rates of snails were 43.02% (77/179), 38.69% (77/199), 47.78% (86/180) and 31.02% (58/187) 14 days following chemical treatment in groups A, B, C and D, respectively (χ² = 11.646, P < 0.05), and there were differences detected in the snail mortality between group A and D, and between groups C and D (both P_adjusted values < 0.05). The adjusted mortality rates of snails were 37.42%, 36.07%, 38.85% and 40.40% in groups A, B, C and D 14 days post-treatment, and the density of living snails decreased by 48.10%, 63.29%, 67.09% and 69.62% 14 days post-treatment relative to pre-treatment, respectively.

Conclusions: Chemical treatment with drones is feasible for O. hupensis snail control in marshland areas; however, the molluscicidal effect of spraying 5% niclosamide ethanolamine salt granules with drones is comparable to spraying chemicals manually in marshland areas regardless of environmental cleaning.