Cyanogenesis inhibits active defense reactions in plants.

@article{Lieberei1989CyanogenesisIA,
  title={Cyanogenesis inhibits active defense reactions in plants.},
  author={R Lieberei and B Biehl and Anette Giesemann and N T Junqueira},
  journal={Plant physiology},
  year={1989},
  volume={90 1},
  pages={33-6}
}
In the course of fungal attack on the cyanogenic rubber tree (Hevea brasiliensis Muell.-Arg.) HCN is liberated from infected tissue. The HCN interferes with plant host and fungal pathogen. It becomes inhibitory to active defense responses which are dependent on biosynthetic processes as far as a threshold concentration is transgressed.