Invasive snails immune to pesticides in central Vietnam

Tran May sits by his rice field with the golden apple snails in his hand, January 2021. Photo by VnExpress/Pham Linh.

Despite trying out both powder-based and liquid pesticides, Tran May, 70, is still met by scores of newborn golden apple snails.

May lives in Nghia Thuong Commune of Tu Nghia District, where the snails have been wreaking havoc across fields and irrigation canals for weeks.

"The snails appeared around 20 days ago and we’ve been trying different pesticides to get rid of them and stop their spread, but with little result," he said.

May has spent VND500,000 (over $20) on pesticides, along with five days recultivating young rice plants destroyed by the snails in their 1,500-square-meter rice field.

Most rice fields in the neighborhood suffer the same problem, with farmers trying in vain to catch the snails to feed their chickens and ducks.

Excessive pesticide use has left a chemical odor in the air, with packaging lying strewn along canals.

"If I caught some today, others would simply take their place," another farmer in Nghia Thuong Commune said.

She said the snails have attacked not only the rice plants but her chili crop too.

Originating from South America, the golden apple snail was imported to Vietnam from 1985 to 1988 with the intention of raising it for human consumption.

Not long after, the snails had spread to most freshwater ecosystems across the country, threatening wetland rice and vegetable crops, among others. The Global Invasive Species Program lists golden apple snail as one of the world's 100 worst invasive alien species.

Golden apple snails can live up to six months in drought condition and rapidly multiply within reach of water. They could lay eggs at a speed of 200-300 in about three hours. This species often feeds on young rice plants or young shoots right after sowing up until the crops are 30 days old.

Young golden apple snails after destroying a rice field in Tu Nghia District of Quang Nam Province, January 2021. Photo by VnExpress/Pham Linh.

Farmers blame the prolonged and historic flooding that had ravaged the central region last October and November for the excess of golden apple snails this year.

Le Thanh Tra, from the Agricultural Service Center of Tu Nghia District, said golden apple snails have appeared in almost every commune.

But he warned farmers to limit the use of chemicals to get rid of the pest, instead suggesting the use of water spinach and breadfruit fiber along with bamboo steaks to lure and capture the animals.

According to Quang Ngai Plant Protection Department, farmers across the province have cultivated rice on a total area of 40,000 hectares (almost 99,000 acres) for the winter-spring crop and so far, 500 hectares have been damaged by the snails. Tu Nghia District has been hit hardest with 215 hectares destroyed.

Pham Ba, head of the department, said it has provided guideline on how to safely get rid of the snails, either chemically or manually.