Last year, Kew's arboretum team destroyed 185 nests in 45 trees, but this year around 500 nests have been found in almost 100 oaks - which would take 1,500 hours to remove.
Arboretum head Tony Kirkham said: "The numbers have increased because nothing has been done to treat them outside of Kew. A few have been moved outside but as long as some remain in private gardens between Kew and St James's Park, it doesn't matter how many are removed at Kew - they won't be eradicated.
"At the moment the moth is pres-ent in Richmond, Ealing, Hounslow and Hammersmith but it will spread further and more councils will face the same situation.
"My priority is removing the threat to staff and visitors, and we will tackle the large, active nests."
He concluded: "I'm quite relaxed. I don't see a lot of feeding damage and think it would have to get to epidemic proportions to cause severe damage to the tree collection. I don't see the current levels as a major threat because, if it's dealt with early enough in the season, there is time for the trees to put on a second flush of leaves."
Kew scientists in the Jodrell Laboratory have been studying oak processionary moth since its first appearance in the gardens in 2006. Kirkham is a member of the Forestry Commission's Outbreak Management Team.