The fourth blaze destroyed a barn at Tarring Neville on November 7th.
A man has been arrested in connection with a series of barn and hay bale fires in East Sussex.
Four roadside barns were deliberately targeted in Beddingham, Alfriston, Tarring Neville and Litlington, between 2 and 7 November 2021.
An 18-year-old man was arrested on Saturday on suspicion of arson and conspiracy to commit arson.
He has been interviewed and released under investigation.
Sgt Jon Attfield from Sussex Police's rural crime team described the crimes as "highly destructive".
Police continue to appeal for witnesses to any suspicious activity in the area between 2 to 9 November 2021.