A British expert says a major review is needed of how countries handle the importation of plant materials, to protect their forests from devastating diseases.
Professor Clive Brasier is in New Zealand for an international meeting which has been discussing the threat of phytophthora, known as the "destroyer of plants".
The insidious pathogen is often difficult to detect, sometimes not creating any problems until it's introduced to a new environment in a new country.
Professor Brasier says there appears to be a surge an activity of invasive phytophtora in recent years, including the sudden oak death disease in the United States and Europe, and a die back in kauri trees in New Zealand, as a result of increase in international trade of plant material.
He says current international rules governing plant imports date back to the 1950s and are not rigid enough to protect countries from the threat of micro-organisms.
Professor Brasier would like to see a review of international plant health protocols.