Watching workers poke avocados from the treetops in an orchard owned by Kenyan agriculture firm Kakuzi, MD Chris Flowers revels in the thought some might soon go to the crown jewel of emerging consumer markets: China.

Taking advantage of Beijing’s deeper focus on trade with African countries to help reduce gaping deficits, Kenya struck an export deal with China for avocados in January after years of lobbying for market access.

Six months later, no shipments have left, Kenya’s avocado society, the East African country’s plant health inspectorate and Kakuzi said...