The Swansea Bay Rally, postponed last month due to a tree disease, has been cancelled for 2010, say organisers.
The event, due to start and finish outside Swansea Museum on 17 July, was called off at short notice.
The route, near Resolven and Rhondda, went through areas that have been hit by the Phytophthora ramorum infection, also known as as "sudden oak death".
Rally organisers said the event could not be re-scheduled to take other qualifying rounds into account.
The rally, which has been running for almost 40 years, is part of the MSA National Gravel Rally Championship.
Around 80 semi-professional and club drivers were due to take part.
It was postponed early in July after a request from Forestry Commission Wales which feared there would be a high risk of spreading the disease with cars travelling between infected woodlands and uninfected areas several times.
Rally organisers said there were additional concerns about the availability of accommodation, the ability of new routes to avoid affected areas and the re-issue of documentation for the event.
Clerk of the Course Alan Stoneman said: "We are all very sad to lose the rally for 2010, but the combinations of circumstances are too great to resolve.
"All the elements had to slot into place and regrettably that could not be done and the threat that this infection was still spreading was not helping."
The infection has been confirmed in Japanese larch trees in woodland managed by Forestry Commission Wales in the Afan Valley near Port Talbot, in Garw Valley near Bridgend, and the Vale of Glamorgan.
The outbreak is the first timethe tree disease has been found on Japanese larch trees outside of south west England
A £600k support package has been announced to fight the disease.