As a second case of Phythophthora lateralis is reported in Scotland, the Forestry Commission has warned the disease could have serious implications for the ornamentals industry if it takes hold.
The finding in Lawson cypress trees at Greenock Cemetery in Inverclyde follows an initial outbreak last December on Lawson cypress at Balloch Castle Country Park at Loch Lomond.
The new head of the commission's plant health service John Morgan said: "We've been on high alert for P. lateralis since it was first discovered at Balloch and we feared it might turn up elsewhere. Sadly, that has proved to be the case.
"Lawson cypress, especially its colourful cultivated varieties, is much enjoyed in British gardens and parks, and this disease could have serious implications for the ornamental plant industry if it becomes established here."
He said the key to controlling the virulent disease was constant vigilance by tree and woodland owners and managers, and he recommended people to report any unexplained dieback of Lawson cypress to the commission's tree health diagnostic and advisory service.
East Lothian-based Alba Trees managing director Rodney Shearer said he didn't see P. lateralis as a major threat, but the spread of P. ramorum has impacted on the business bringing Japanese larch production to a halt.
"As nurserymen we are adaptable. But the worrying thing is how to plan for the future because if customer demands change, a nursery needs to be a few years ahead," he said.
Weasdale Nurseries partner Andrew Forsyth said: "If the Forestry Commission is concerned, I would take heed. At times like these it's very important hygiene is observed properly and that people who come across the disease handle it responsibly.
"Lawson are prone to Phythophthora but this is a new strain. At the moment we have three pages of Lawson cypress in our catalogue, so it would hurt if it hit."
P. lateralis is a native to California and Oregon, and mostly affects Lawson cypress trees. The symptoms are foliage appearing lighter in colour, before withering and turning reddish-brown.
P. ramorum has a wide host range and has resulted in the felling of more than 2 million Japanese larch trees. Symptoms vary on each different species.
P. kernoviae has been linked to rhododendron and European beech. Symptoms vary depending on plant species.