Railway departments, customs and companies have formed special teams for the transport of fresh fruit. Green channels for inspection give priority to entry, inspection and testing, linking arrival, clearance and transfer more smoothly and sharply reducing the time fruit spends at the port.

Nansha, China's largest seaborne port for durian imports, is making a similar effort. As Southeast Asia's main producing areas enter peak season, its durian imports are expected to keep rising between April and June.

Yet scale has not reduced scrutiny. For the concentrated arrivals in late April, customs officers carried out targeted inspection and quarantine, checking for harmful organisms and taking samples for pesticide residues, heavy metals and other safety indicators.

"Visible pest risks can be checked by the eye, but invisible microbes and contaminants must also be strictly guarded against," said Lin Xiaojing, an official with Nansha Customs.

As a result, the market is expanding not only in size, but also in standards. Niti Pratoomvongsa, commercial counselor at the Royal Thai Consulate-General in Nanning, capital of South China's Guangxi Zhuang autonomous region, said Chinese consumers are shifting from a focus on price toward a stronger concern for quality, food safety, production standards and traceability. This change is raising the bar for competition.

Southeast Asian suppliers are responding. As planting areas expand in Thailand, Vietnam, Malaysia and Cambodia, industry participants say the competition among Southeast Asian suppliers in China is still being reshaped.

Chinese capital and business operators are also moving further upstream. Liu Junhong, a Guangxi businessman who shifted from engineering and agricultural irrigation into durians five years ago, has inspected markets in Malaysia, Thailand and Vietnam and invested in a planting project in Cambodia's Kampot province.