Bulmers area farms manager Ben Moss said: "It's a massive problem here, though sporadic, and generally on the more challenging sites. As trees age they often grow through it. But it has necessitated more removal than we would like."
East Malling Research fruit pathologist Dr Angela Berrie, who has monitored the disease at Penrhos, said: "This is a fairly isolated site. Infection in the trunk is likely to have occurred in the nursery, while peripheral infection is more likely to have been acquired on site."
She continued: "Cider orchards seem to recover better, perhaps because of the different production methods. Many modern dessert varieties are susceptible, particularly in high-intensity plantings - and all the effective products against it have been banned or had their dosage reduced."
An AHDB Horticulture project has recently begun to look at canker "right through from the nursery, where you hardly ever see it, through to when it expresses itself when planted out", added Berrie. "It won't appear at all sites so is it down to rain or aspect? We don't know."
Tree supplier John Worle added: "I am very careful on the nursery and would be keen to solve the problem, if indeed I have it."
He suggested that it may ultimately be a rootstock problem, to which Berrie said: "There is very little rootstock production in the UK. But we want to look at rootstock susceptibility also."