Plants get sick just as we do. Basically, the same types
of organisms act as the pathogens but in differing
degrees. In plants, fungi are the causative agent in the
vast majority of diseases. Perhaps as much as 90% of all
diseases common to plants are caused by these
microscopic, spore producing organisms.
Bacteria are responsible for a handful of diseases.
The most important to home landscapes is probably
fireblight which is a serious disease of members of the
Rosaceae Family including ornamental pears
(Pyrus),
firethorn (Pyracantha) and mountain ash
(Sorbus).
Viruses cause a few diseases with the most serious
being so-called "yellows" diseases. They also cause
growth distortion and leaf mottling in
hostas,
roses and
others.
Here are some topics on common diseases of landscape
plants:
