Seedling broadcasting as a potential method to reduce apple snail damage to rice

Exotic apple snails (Pomacea spp.) are a major threat to the productivity and profitability of rice farming globally. Cultural methods that are applicable to traditional rice transplanting are often successful in reducing snail damage to rice. However, high labor and irrigation costs associated with transplanting highlight the need to develop modern rice crop establishment methods to replace traditional, labor-intensive methods. This study examined four broad categories of rice crop establishment for their vulnerability to apple snail damage. Seedlings from dapog nurseries and wet-direct seeding were highly vulnerable to damage and produced no grain in snail-infested ponds in the Philippines. Rice transplanted from dry bed nurseries at 21 days after sowing (DAS) had high mortality (85%) and consequently low yields. In contrast, seedling broadcasting (21 DAS) significantly reduced rice vulnerability (22% seedling mortality) to snail damage compared to all other methods and resulted in the highest grain yields per plot in our experiments. We attribute lower vulnerability to snail damage and successful stand development to reduced transplanting shock at the time of seedling broadcasting and to the generally good condition of seedlings even after 21 days in polyvinyl chloride trays. We suggest that seedling broadcasting be considered as a crop establishment method with potential to sustainably manage apple snails in irrigated rice.