The invention relates to the polyalkylene oxide derivatives of formula (I), wherein the symbols and indices are defined as follows: R<SUP>a </SUP>is a C<SUB>8</SUB>-C<SUB>30 </SUB>hydrocarbon group; R<SUP>b</SUP> is a C<SUB>8</SUB>-C<SUB>30 </SUB>hydrocarbon group such as C<SUB>8</SUB>-C<SUB>30 </SUB>alkyl, C<SUB>8</SUB>-C<SUB>30 </SUB>alkenyl, C<SUB>8</SUB>-C<SUB>30</SUB> alkinyl; a is 0 or 1; b is 0 or 1; c is 0 or 1 and A represents one or more alkylene oxide entities. The derivatives according to the invention are suitable for enhancing penetration of fungicidal agents into plants.