Plant viral disease preventive alginate containing compositions

摘要

A plant viral disease preventive composition contains an alginate, as active ingredient, having properties of: (a) neutralization degree of 10 to 30%, said neutralization degree (wt %) being given from: <IMAGE> where (C5H7O4COOH)n is the molecular formula of the alginate, m is the number of the carboxylate groups in one molecule of the alginate, and M is an alkali metal or ammonium group; and/or (b) viscosity in a 1 wt % aqueous solution at 20 DEG C. is 2 to 10 centipoises.