A burn ban has been declared for Monterey and San Benito counties.  Cal Fire has suspended all open burning as of today due to the increased threat of fire danger.   Officials say lack of rain and unseasonably dry conditions continue.   Agricultural, land management, fire training and other industrial-type of burning is allowed, with a special permit.   Meanwhile, the ban falls on the heels of the Pfeiffer Fire, that charred 917-acres, and destroyed 34-homes this month in the Big Sur area.   A burn ban was issued yesterday for Santa Cruz County.