Safety and efficacy of quinoa (Chenopodium quinoa) saponins derived molluscicide to control of Pomacea maculata in rice fields in the Ebro Delta, Spain

Pomacea spp. are freshwater gastropods that significantly reduce rice productivity around the world, particularly in Asian countries. Pomacea maculata was first reported in Europe in 2009 in the rice fields of the Ebro Delta, Tarragona (Catalonia), Spain. At present, tea seed (Camellia oleifera) saponins are the only authorized treatment by the Spanish agriculture authorities, but due to its comparatively high toxicity to non-target species such as fish, more environmental-friendly products are urgently needed. This study evaluated the performance of a novel molluscicide based on modified saponins derived from quinoa (Chenopodiurn quinoa) husks against Pomacea maculata under laboratory and field conditions in the Ebro Delta. Under laboratory conditions, the molluscicide killed 100% of the P. maculata above 7 ppm of saponins after 72 h. Field trials performed in three rice fields showed that after 96 h the molluscicide killed 88, 89 and 93% of P. maculata at doses of 6.5, 7.2 and 7.7 ppm saponin, respectively. Toxicological assays showed that the product is highly safe for aquatic environments, with an effect concentration of (EC50) > 36 mg saponins/L for crustaceans (Daphnia) and algae (Selenastrum capricornutum) and a lethal concentration (LC50) against common carp > 36 mg saponins/L. Studies on rats, rabbits and guinea pigs showed that the molluscicide is generally non-hazardous for acute oral toxicity, slightly hazardous for acute dermal toxicity, a moderate irritant for acute eye irritation/corrosion, a non-irritant for acute dermal irritation/corrosion and a non-skin sensitizer. These results suggest that this novel molluscicide may be a viable product to safely control P. maculata in rice fields.