Jan 18 (Reuters) - The Baltic Exchange"s dry bulk sea freight index (.BADI) dropped to an 11-month low on Tuesday, pressured by weaker demand across all vessel segments. * The overall index, which factors in rates for capesize, panamax and supramax vessels, fell 87 points, or 5%, to 1,644, its lowest level since mid-February. * The capesize index (.BACI) dropped 153 points, or 10.5%, to 1,316, its lowest since February. * Average daily earnings for capesize vessels, which transport 150,000-tonne cargoes such as iron ore and coal, dropped by $1,277 to $10,913. * The panamax index (.BPNI) slipped 103 points, or 4.4%, to its lowest since April at 2,223. * Average daily earnings for panamax vessels, which ferry 60,000-70,000 tonne coal or grain cargoes, fell $924 to $20,011. * The supramax index (.BSIS) eased 24 points to 1,840.