The move came after eight Chinese nationals were deported from Chau Thanh District last year for violating regulations that require foreigners in Vietnam to get a permit from local authorities before they do business in that area.
These people had applied for a temporary residence permit in the district under tourist visas but had conducted business activities, such as visiting dragon fruit plantations to buy fruits and flowers and to conduct market surveys.
The local people were also urged to report to police immediately if they saw any Chinese nationals with tourist visas coming to dragon fruit trading zones to buy the fruit, as it is against the law.
The district's authorities called on the relevant agencies to collaborate with police and keep a close watch on the activities of Chinese nationals.
Some farmers in An Luc Long Commune said there were a number of foreigners visiting their dragon fruit plantations but none of them had asked to buy the fruit. They said they would not sell their fruit to traders from other countries to mitigate risks.
Farmer Nguyen Van Ut said local farmers chiefly sold their fruit to Vietnamese traders who would then export it to other countries or resell it to other customers.
Farmer Vo Thi Kim Lien said some farmers used to sell dragon fruit flowers, but this has now changed and they currently only sell fruit.
Nguyen Van Thinh, Chairman of Chau Thanh District's People's Committee, said apart from the Chinese nationals who were deported from the district for violating regulations, local authorities had not yet found any Chinese traders directly making deals with local farmers to buy dragon fruit or flowers.
Rumours that Chinese traders have caused prices to fall and manipulated the market are unfounded because at present, the price of dragon fruit, particularly red dragon fruit, is high and has been stable for the past few months, he said.
Last year, local farmers flocked to sell their dragon fruit flowers to traders, but they then stopped the practice as the sales affected their crop output, according to Thin.
There are more than 6,400ha of dragon fruit plantations in the district.