Marc Veltenaar of Dutch salad grower association Quality Queen Sales said cucumber sales to the UK were in decline.
"Right now, they (Britain) prefer their own product," he said.
"They only buy abroad if they experience shortages, which is rarely."
Russia remains a volatile market, with Dutch exports slumping 35 per cent in the same period.
But onions, which are recorded separately, bucked the trend with a 19 per cent rise in exports to the UK to 60,000 tonnes. This accounts for nearly 13 per cent of exports, which grew 20 per cent overall in the period.