The yellow-spined bamboo locust (Ceracris kiangsu) swarm, which has an estimated 100-400 individuals per square meter, devoured bamboo leaves in 20 ha of forests in Po Nhu Kho and Ta Mieu villages in Muong Nhe District, Nguyen Trong Kinh, head of the province plant protection department, said on Friday.

They then moved on to corn fields, also spanning 20 ha, he said.

The department has sent personnel to the area to monitor and destroy the swarm, he said.

The insects have been making an appearance since 2015, often flying in from Laos in waves, but this is the first time they are coming from China, he said.

"It might be because Chinese localities near the border have been spraying pesticides. All individuals in the swarm are adults, which would breed and continue to spread."

Dien Bien, which borders Laos and China, is not the only Vietnam locality affected by locusts. Other border provinces like Son La, Cao Bang and Thanh Hoa also typically see swarms of yellow-spined bamboo locust every July, Nguyen Quy Duong, deputy head of the Ministry of Agriculture and Rural Development’s plant protection department, said.

"They only like to eat bamboo leaves and the like. If there are no bamboos, they destroy corns. Hopefully they will leave in a few days and the plants can recover."

The National Committee for Incident, Natural Disaster Response and Search and Rescue said it has requested the High Command of Military Region 2 to monitor the swarm’s movement and assist locals in destroying it if necessary.