Whilst in the States late 80's was told that early post WWII B17s were used for crop spraying against large infestations of particular insects over the Mid-west. Believe they even did it in a formation of a few aircraft in echelon to get good coverage, due inability to tight turn back onto the next spray line.
They also used them for fire fighting. Flew in one of the last ex-fire fighters still in it's FF livery. N17F I seem to recall was its reg. The only airworthy B17F at the time, now I believe grounded and in the Boeing museum. It did though make it over to the UK to take part in Memphis Belle as 'C-Cup'.