THE PILOT REPORTED THAT HE WAS CONDUCTING SPRAY OPERATIONS. VISIBILITY WAS REDUCED TO ABOUT 3 MILES BY HAZE AND IT WAS DUSK. ON PULL-UP FROM A SWATH RUN, HE SAID, THE AIRPLANE'S DISTANCE FROM THE TOP WIRE OF A CROSS COUNTRY POWER LINE WAS MISJUDGED. THE LANDING GEAR CAUGHT THE WIRE AND A FORCED LANDING ENSUED. CONTACT WITH THE WIRE AND THE FORCED LANDING RESULTED IN SUBSTANTIAL DAMAGE TO THE AIRPLANE.