The present invention relates to dsRNA molecules for inhibiting the expression of CYP51 gene(s) from a fungal or oomycete phytopathogen and the use of such inhibitory dsRNA molecules for controlling phytopathogenic fungi and/or oomycetes. The present invention further relates to DNA sequences providing a transcriptional template for inhibitory dsRNA molecules or antisense RNA; and phytopathogen-tolerant transgenic plants with such DNA sequences.