Hung, a farmer who owns 3 hectares of VietGAP (Vietnamese Good Agricultural Practices) certified durian in central highlands province of Lam Dong, said that two years ago, traders had to compete to get his fruits for export to China.

However, in the last two months, traders have been insisting on certification of origin for the fruits.

"Because of China's new import restrictions, I have to join a co-operative to get my fruit stamped. I will get this done by early June," Hung said.

Lai The Hung, director of Lam Dong’s Department of Crop Production and Food Protection, confirmed that China was changing its import regulations.

Hung told VnExpress that exported fruit had to meet China’s technical and phytosanitary standards, as well as regulations on food safety.

Importers must declare and provide stamps showing the origin of fruit brought in, and register with Chinese customs an area code showing where the fruit was planted. Exported fruit must also meet standards in packaging and hygiene, including being pest-free.       

The Agro Processing and Market Development Authority under the Ministry of Agriculture and Rural Development also affirmed that China has changed many regulations on Vietnamese fruit imports.

From January 10, all packages of food imported into China required a Food Safety Certificate issued by an authorized organization from the exporting country. 

"The Chinese government is under pressure from its own people to raise standards," said Dr Bui Chi Buu, a former director of the Southern Institute of Science and Technology.

Vietnam's fruit and vegetable exports to China decreased by 6.3 percent year-on-year to $680 million in the first quarter of 2019, according to the Ministry of Agriculture and Rural Development.