The frosts have hindered the harvesting of new season navel oranges in two of Australia's major orange growing regions. "The Riverland and Murray Valley regions have experienced severe conditions. This has slowed fruit picking and packing rates for all markets," said Australian Citrus Growers (ACG) president Mark Chown. He said the conditions were the "worst frost event since 1982". Initial crop assessments in Murray Valley and Riverland suggest that there will be a 20 per cent drop in navel orange production, although the industry said it could not yet tell whether this would impact prices. The naval harvest is about 15 per cent completed but the frost has stopped the harvest. Effects on the Valencia crop will not be known until later this year, as this crop is harvested later. Industry had forecast a 3 per cent increase from last season in the Australian navel crop to 240,000 tons and a 26 per cent drop in Valencia to 202,150 tons. But it is now checking fruit for freeze damage. "This is a real blow for growers who have already experienced a number of poor seasons. However, it is imperative that growers and packers take all precautions to maintain pack out rates and consumer confidence," added Chown. Export forecasts for the US market and soon-to-be opened China market have however been reduced. Australia signed a new quarantine protocol for the export of Australian citrus to China in April. It estimates that trade of oranges, mandarins and lemons with China could be worth $A50 million.