Hertfordshire-based Majestic is in the OPM buffer zone.
McCurdy, who is travelling more early in the year to source stock ahead of the 29 March EU leaving date, said he thinks it is a "high probability" that OPM will be "parachuted" through direct imports to landscaping sites around the country outside London, where it is established.
Overseas growers have been losing sales, while some UK growers want a full ban on oak imports.
He said 'straight to job site' sales are the "big weakness" in the system and to send oaks to nurseries gives a better chance of controlling OPM.
McCurdy said: "There is lax control on the continent where its everywhere."
He added: "It is highly probable there will be a ban on direct imports of oaks after 29 March to job sites for landscapers."
In August 2018, new regulations banned the movement of certain oak trees into the UK’s OPM Protected Zone (an area of the EU declared free of the pest) unless specific conditions centring around being grown in non-OPM areas, are met.
They cover both imports from overseas and movement of trees from areas of the country where OPM is already present – in London and surrounding counties.
