EMC Insurance Group Inc. on Thursday revised its third-quarter earnings estimate upwards, saying it expects lower third-quarter catastrophe losses will be partially offset by losses associated with its crop reinsurance program. The Des Moines-based property/casualty insurer said it expects premium income to increase by approximately 13.2 percent and for after-tax catastrophe losses to decline to approximately 55 cents per share in the third quarter, compared to $1.33 per share in the year-ago quarter. The company has revised its 2012 operating income guidance from the previous range of $1.30 to $1.55 per share to a revised range of $2.05 to $2.30 per share.