The influence of natural organic substances as humate colloidal aggregates in water solutions upon the chemical stability of vinclozolin has been investigated in basic media. A large inhibition (9 times-fold) has been observed and it has been rationalized in terms of a micellar pseudophase model. The observed behaviour could increase significantly the half-life of this fungicide. Moreover, these experimental results have been compared with the corresponding ones of other substances in these natural colloidal aggregates. (C) 2015 Elsevier B.V. All rights reserved.