Evaluation of poison baits and development of a containment trap for the management of terrestrial snails

Introduction

Gastropods, particularly terrestrial snails and slugs, represent a highly destructive polyphagous pest complex capable of consuming over 500 varied plant types (Jadhav et al., 2016; Bhattacharyya et al., 2014) [2,1] . Fuelled by simultaneous hermaphroditic reproduction and extended aestivation cycles, massive nocturnal populations aggressively devour vulnerable plant parts, triggering severe economic deficits in commercial agriculture (Bhattacharyya et al., 2014; Chavan, 2024) [1,3] . In Maharashtra, population explosions of the giant African land snail (Achatina fulica) have compromised over 72,000 hectares of Kharif plantings, disproportionately devastating soybean and legume crops (Neharkar et al., 2025) [4] . Standard mitigation protocols relying on the generalised broadcasting of synthetic chemical molluscicides, such as metaldehyde pellets, face profound practical limitations; these chemicals degrade rapidly during heavy monsoon rains, lack natural olfactory attraction, and pose toxicity risks to non-target ecosystems (Sallam et al., 2012; Patil et al., 2015; Smith et al., 2013) [6,5,7] . Overcoming these challenges necessitates the development of specialized, odour-based attractant matrices that fuse toxicants with vigorously fermenting food bases, such as beer or fruit waste, to actively draw pests from their daytime refuges (D'Souza, 2025; Veasey et al., 2021) [8,9] . Furthermore, housing these attractants within enclosed physical structures protects the active ingredients from intense weather degradation and prevents target escape (Roda et al., 2018; Minott et al., 2018) [11,10] . Therefore, the present investigation was undertaken to compare the efficiency of different fermenting poison baits and to develop a customised, weather-resistant physical trap for the optimised management of snails in soybean fields.

Materials and methods

Experimental Site and Treatment Details:

The field experiments were conducted during the Kharif 2025 season in a naturally infested soybean (Glycine max L.) plot located in Sadoli Khalsa, Kolhapur district, Maharashtra. The trials were laid out in a Randomized Block Design (RBD) comprising seven treatments replicated three times. The treatments were formulated by supplementing specific food bases with 20 g of active dry yeast (acting as a fermenting olfactory attractant) and 50 g of 2.5% metaldehyde dry pellets (acting as the toxicant). The specific attractant bases evaluated were: 400 ml beer (T 1 ), 250 g wheat bran with 250 ml water (T 2 ), 250 g rice bran with 50 g jaggery and 250 ml water (T 3 ), 500 g papaya fruit with 100 ml water (T 4 ), and 500 g cabbage leaves with 100 ml water (T 5 ). These were tested against a standard chemical bait consisting of 200 g metaldehyde pellets with 200 ml water and 20 g yeast (T 6 ), alongside an untreated water control (T 7 ).

Open baiting evaluation (Phase I)

To assess the baseline efficiency of the poison baits without physical containment, the formulations were placed randomly within the designated experimental plots (5.0 m × 4.0 m), maintaining a sufficient buffer to prevent cross-interference. To preserve optimal trapping efficiency and bait freshness in the open field, each poison bait was completely replaced at 2-day intervals. Field observations were recorded by physically counting the number of dead snails on and immediately surrounding the baits at sequential intervals of 2, 4, 6, 8, 10, and 12 Days After Placement (DAP).

Trap construction and evaluation (Phase II)

To mitigate environmental degradation of the baits, a customized physical trap was fabricated using a cylindrical plastic container measuring 25 cm in total height, 16 cm in basal width, and featuring a 20 cm pull-open lid. Three rectangular access windows (13 cm height × 9 cm width) were cut into the sides, strategically positioned 6 cm above the base to retain an intact bottom reservoir for holding toxic liquids without soil seepage. The cut window materials were bent outward to create extending ramps. The traps were buried in a 6 cm deep soil pit, allowing the entry ramps to rest completely flat on the ground, creating a continuous moisture gradient that guided nocturnal snails into the enclosure. A string mechanism was installed to pull the ramps closed during lid removal, preventing spillage during maintenance. The seven previously described poison bait formulations were placed inside these traps and replenished at 4-day intervals. The absolute number of dead or trapped snails was recorded at 3, 6, 9, 12, 15, and 18 DAP. Snail entry ramp

Statistical analysis

The raw trap catch data recorded from each replication across all observation intervals were compiled independently. To normalise the variance, the data were subjected to square root transformation using √𝑥 + 0.5 . The transformed data were analyzed utilizing Analysis of Variance (ANOVA) for RBD, and the significance of treatment variations was tested using the F-test at a 0.05 probability level.

Result and discussion

Efficacy of poison baits under open field conditions

Field evaluations demonstrated that combining 2.5% metaldehyde with actively fermenting dietary substrates drastically improved target capture rates compared to utilizing the standalone chemical or unbaited controls. The beer-infused formulation emerged as the most potent olfactory attractant, securing the highest overall mean catch of 10.44 snails per observation. This was closely followed by the wheat bran matrix, which achieved an overall mean of The overwhelming superiority of the beer and wheat bran baits confirms that highly fermentable liquid and carbohydrate mediums are optimal gastropod attractants. The addition of yeast accelerates fermentation, releasing concentrated volatiles that successfully draw snails from greater distances, a dynamic strongly supported by Patil et al. (2015) [5] and Suzuki et al. (2025) [12] . Furthermore, the poor performance of standalone metaldehyde confirms that the toxicant itself is a weak attractant and routinely suffers from severe palatability deficits when natural vegetation is readily accessible, aligning with findings by Smith et al. (2013) [7] and Laznik et al. (2010) [13] . Similarly, the cabbage bait failed because it presented no distinct aromatic contrast to pull snails away from the dense, established soybean canopy.

Table 2. Efficiency of different poison baits against snails under open conditions

Sr

Performance of the custom snail containment trap

When these identical toxic mixtures were housed inside the customfabricated cylindrical traps, capture frequencies surged significantly.

The beer bait trap remained the most effective treatment, recording a peak overall mean catch of 15.39 snails per trap. The wheat bran (13.56 snails) and fruit baits (12.17 snails) also maintained their highperformance rankings inside the enclosures. Transitioning the baits into the engineered devices yielded an immense relative performance increase across all treatments when benchmarked against the exposed layouts. Rice bran generated the steepest percentage jump among the dietary baits (55.95%), followed by beer (47.41%), wheat bran (42.74%), and fruit (42.17%). Even the weaker cabbage and standalone metaldehyde variants experienced capture boosts of 39.85% and 28.98%, respectively. These analytical findings confirm that the engineered containment unit cultivated an optimal, shaded microclimate that served as a highly attractive artificial aggregation zone during daytime thermal stress. By sinking the trap base 6 cm into the soil, the device established an uninterrupted damp pathway that guided nocturnal snails directly up the flanged entry ramps. Existing literature thoroughly en dorses these structural advantages; Raudenbush et al. (2021) [14] and Rabelo et al. (2022) [15] confirmed that modified pitfall frameworks with moisture reservoirs create significantly cooler microclimates that aggressively pull in heat-averse gastropods. Most essentially, elevating the side access windows generated a fully sealed lower basin. This design stopped the lethal fluid mixtures from leaching into the soil, shielded the fermenting attractants from intense monsoon downpours, and entirely thwarted intercepted pests from escaping, mirroring the highly successful bucket trap mechanics validated by Minott et al. (2018) [10] and Roda et al. (2018) [11]

Summary and conclusion

The present investigation evaluated the efficacy of various fermenting poison baits and the structural advantages of a custom-engineered containment trap for managing terrestrial snails in soybean ecosystems. Under open field conditions, blending 2.5% metaldehyde with actively fermenting carbohydrate or liquid substrates-particularly beer and wheat bran-drastically improved target capture rates compared to utilizing standard chemical pellets in isolation. The beer-infused formulation emerged as the dominant olfactory attractant, securing an overall mean catch of 10.44 snails, which translated to a 2.73-fold surge in capture capability relative to the baseline metaldehyde layout. Conversely, metaldehyde and cabbage-based attractants yielded weak interception rates, proving that bare chemical agents lack sufficient sensory pull within densely vegetated agricultural environments.

To circumvent the ecological and structural vulnerabilities of exposed bait stations, a specialized, weather-resistant cylindrical trap was developed. Situating the toxic baits inside these physical enclosures catalyzed substantial interception surges across every tested group, with the beer-infused trap achieving a maximum aggregate average of 15.39 snails per unit, representing a 47.41% increase over open baiting. The trap's design-featuring a sealed lower liquid reservoir, extended entry ramps, and an overhead canopy-successfully halted chemical drainage into the soil, shielded the aromatic components from harsh solar rays and torrential rains, and entirely thwarted intercepted individuals from escaping. Ultimately, the research solidifies that maximizing pest eradication requires physically blending killing agents into a vigorously fermenting matrix and housing them within specialized physical enclosures to ensure reliable, long-term population mitigation.

Acknowledgement

AcknowledgementsI gratefully acknowledge the Department of Entomology, Rajarshee Chhatrapati Shahu Maharaj Government College of Agriculture, Kolhapur, for providing the facilities to conduct this research and thank all teachers, technical staff and colleagues for their support and cooperation.

References

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