The present invention relates to novel active substance compositions for plant protection in the form of finely divided active-substance-containing particles which compositions comprise a) at least one plant protectant; b) at least one polymer P which is not soluble in water and which is degradable by enzymatic hydrolysis, in an amount of at least 20% by weight based on the total amount of the components of the active-substance-comprising particles, and c) at least one hydrolase (EC 3),where at least 90% by weight of the active substance-containing particles of the active substance composition do not exceed a diameter of 500 .mu.m (D.sub.90-value) and where components a), b) and c) account for at least 30% by weight of the active substance particles. The invention also relates to a process for their preparation, and to the use of the active substance compositions for the treatment of plants, soils and of seed.