Hundreds of farmers in Mang Ri and Tu Mo Rong communes have been taking turns guarding their ginseng farms day and night, setting traps and erecting barriers in an effort to keep the rats out.
A Chung, 35, a farmer in Loc Lai village in Mang Ri, grows nearly 10,000 Ngoc Linh ginseng plants. Since late August, rats have damaged almost 2,000 of them, causing estimated losses of more than VND 400 million.
Chung said the rats gnaw through stems, leaves and roots and are particularly active at night. His family, who previously returned home after tending the farm during the day, now take turns staying in the forest overnight to protect their crop.
Le Nguyen Son, 41, head of Long Tro village in Mang Ri, said nearly 1,600 of his 7,000 ginseng plants had been damaged in recent weeks, with losses estimated at nearly VND 300 million.
The rats mainly eat the roots and leave the stems and leaves behind, Son said. Traps placed along their paths and netting around the farm have so far failed to keep them out.
Pham Xuan Quang, chairman of the Mang Ri Commune People's Committee, said about 300 households had been affected since mid-August, with around 7,500 ginseng plants aged between one and 10 years damaged.
Quang said the farms are spread across mountainous terrain surrounded by natural forest where the rats live, making it difficult to prevent them from entering ginseng-growing areas.
Local authorities have urged farmers to step up protection measures, including night patrols, traps and plastic sheeting around ginseng beds.
In neighbouring Tu Mo Rong commune, more than 1,000 Ngoc Linh ginseng plants have been damaged, according to Duong Dang Khoa, vice-chairman of the commune People's Committee.
Farmers there have also resorted to traps, night patrols and metal sheeting around cultivation areas to keep rats out.
Khoa said Ngoc Linh ginseng was a high-value crop that takes years to mature, meaning damage to plants during their growing period can cause substantial losses.
Ngoc Linh ginseng is a rare medicinal plant that thrives under forest canopy at elevations above 2,000 metres. It is widely grown in mountainous areas including Dak Sao, Tu Mo Rong and Mang Ri, as well as neighbouring areas of Da Nang.
Businesses and local households have expanded cultivation under forest canopy in recent years as a source of income. Ngoc Linh ginseng sells for about VND 80 million to VND 250 million per kilogramme.