Six sheds were destroyed by fire over three nights at the Catchacre allotment site in March, with a further three sheds damaged at the Meadway allotment site in a single night in May.
Now Dunstable Town Council is providing overnight security at the sites in an attempt to catch the arsonist.
And police are urging allotment tenants to remove anything flammable away from their sheds.
A police spokesman said: “During the early hours of this morning (May 12) there were further shed fires within the allotments located near to Cemetery Lane. This is the 16th incident of this nature over a short space of time. The majority of the offences were committed at around 0200 hours. Some 40 minutes later a pile of wooden pallets were also set alight near to Bennett's Rec.
“I would urge anyone with a shed or outbuilding nearby to remove any flammables or combustibles from within until the offender has been apprehended. I would also ask that any piles of rubbish etc are cleared or kept away from buildings.
“If you have CCTV and or ring doorbells within the area it would be worth having a look at around the time stated. Any information would be greatly received. Please quote Operation Volume with any information.”
John Crawley, Head of Grounds and Environmental Services at Dunstable Town Council said the council had been helping allotment tenants clear away the burnt remains.
He said: “The Council has provided overnight security at both sites to try to break the cycle of behaviour. However, this is not a sustainable long-term solution. The Council has spoken with Bedfordshire Police colleagues who are actively investigating the fires as a matter of priority.
“The Council has also spoken with the Community Safety team at Central Bedfordshire Council and has made a request for the installation of temporary re-deployable CCTV cameras.
“Both the Police and the CBC Community Safety Wardens have increased patrols in the area
“All the Council’s allotment sites are fenced and have lockable security gates. Works are currently being examined to replace the chain-link fence at the Catchacre allotment site with a more robust metal palisade fence.”