How can we defend our plants from
dangerous fungi?
How
can we defend our plants from dangerous fungi?
Once
it had been discovered, about 150 years ago, that fungi
caused many plant diseases, the search began for ways to
protect crops from these fungi. It seemed logical to poison
the fungus before it got into the plant. The first fungicides
were inorganic substances, such as sulphur, and salts of
copper.
Unfortunately
these also tended to cause some damage to the plants, and
accumulate in the soil, so a second generation of fungicides
was developed. These were organic compounds which worked
at lower concentrations and caused little or no damage to
the plants.
Eventually
a third generation of fungicides was discovered which are
absorbed into the plant and can kill the fungi even after
they have got inside. These fungicides are more subtle in
the way they work. For example Benomyl, the first of these
'systemic' fungicides, prevented the nuclei of the fungus
from dividing and so stopped its growth completely.
But
that's not the end of the story. Fungi, being true survivors
(after all they've been around a lot longer than we have)
developed resistance to sytemic fungicides, so the search
for new ones goes on.
For
some images relevant to fungicides go to Chapter
13. A much more detailed account can be found in the
book and on the CD
ROM.
Other
ways of combatting pathogenic fungi are described in Chapter
10 and Chapter 14
of the book and CD-ROM.
