The agriculture export value has fallen to $3.8 billion, with rice falling 67.5 percent to $159.4 million and vegetables and fruits dropping by over 8 percent to $1.6 billion, said Tran Thanh Hai, deputy head of the Export-Import Department under the Ministry of Industry and Trade.

The decline has happened after China began tightening its quality and safety standards for imports since earlier this year, he said at a recent forum.

For example, bananas need to be boxed with Chinese labels, or watermelons need to have codes to trace origins, he said, adding that some fruits are only allowed to be imported through specific border gates.

China had announced these regulations in mid-2018 but many businesses did not pay attention, Hai added.

"The new standard is an inevitable global trend. Many other countries are also tightening their import regulations."

However, Vietnamese businesses still operate in small scale and are unable to meet higher quality standards.

Minister of Industry and Trade Tran Tuan Anh said many Vietnamese agriculture exporters to China were unprofessional and depended on unofficial channels.

Many of them are small businesses who are not up to date with the latest information and do not have a stable source of supply, leading to produce being stuck in the country, he added.

Le Hoang Oanh, head of the Asia-Africa market department under the trade ministry, said that it was necessary to make plan to produce each type of agricultural produce for certain export markets on the basis of studies done on the market size, consumer tastes and global trends.

"Exporters need to abandon the mentality of considering China as an easy market, shifting unofficial exports to official, improve fruits quality and facilitate origin traceability."

There are nine Vietnamese fruits allowed to enter China through official channels: dragon fruit, mango, logan, litchi, rambutan, banana, watermelon, jackfruit and mangosteen.

Between January-July, the U.S. replaced China as the top buyer of Vietnamese agriculture produce, according to data from the Ministry of Agriculture and Rural Development.