In Chemical Resistance Part One: HOW? we established that misuse of a chemical intended to fight off a disease can lead to chemically resistant “critters”, or superbugs. I use the word critter to describe any pest that can cause a need for pesticide: be it bacteria, virus, fungus, insect, or weed.
But
WHY would a chemical be used in the wrong way?
There are several reasons:
a.
Only one kind of chemical was used over and
over again in the same place to kill the same thing.
b.
The chemical was used to kill the wrong
critter.
c.
The wrong dose was used, so the chemical
wasn’t effective.
In the first case, if we use
only one chemical, and use it more often, more generations of the critter are
exposed to it, selecting the superbugs faster.
Think of it this way: when a boxer is fighting, he needs to learn
several moves and series of actions in order to take their opponent down. He wouldn’t think of fighting using only a
right handed uppercut, would he? His
opponent would be ready for him, and demolish him right away. They would know what to expect. Same thing with using the same chemical each
time: the critter is prepared, and able to deflect the hit every time! It’s a
superbug!
Remember how I described the
“diversity” of critters that can harm plants (or us)? If you have a virus, and take antibiotics,
the antibiotics won’t kill the virus, because that’s not what the drug was
designed for. It’s made to kill bacteria. And any random bacteria that happen to be
hanging out during your viral infection can hide out and is exposed to this
antibiotic—having the opportunity to save the “memory” of the chemical. So the next time these critters overpopulate
and you have a bacterial infection, that drug won’t treat it as well. The bacteria’s progeny will have a “memory”
of the chemical, and more will survive. Enter: superbugs.
In agronomy, plant diseases
are usually fungi. But there are also
viruses and bacteria that cause plant diseases as well. If we aren’t positive of the source of a
disease, and use a fungicide to try and kill a bacteria or virus disease, the
fungi present—but not causing enough damage to trouble the plant—can develop a
resistance to that fungicide.
In the third case, we see
the importance of dosage. If you read
your small print that comes with your antibiotics, it will urge you to take
your medicine as directed, the full dose, and not to stop even though you feel
better. Why is this? Your doctor wrote you a dose that will
effectively kill the infection that is causing your illness. An effective “chemical storm” that will take
care of those critters. If you stop
early, or don’t take the whole dose correctly, you are diluting the chemical
that the bacteria are exposed to. So
more bacteria will survive: they don’t have to “hold their breath” as long or
as forcefully, so to say, until the chemical storm is over. You might feel better temporarily, but when
more critters survive, more critters have the drug “memory”, and those critters
can create even more critters.
In a field, the agronomist
takes into account many factors, such as the developmental stage of the plants,
the type and severity of the pest infestation, time of the growing season,
weather, and soil conditions. These
factors determine the right kind and dose of pesticide to use. In a similar manner, if not enough of a
pesticide is used, or if it isn’t applied at the correct time, more of the pest
can survive and fight back.
Tune in for the third and
final conversation regarding chemical resistance: WHAT TO DO? for information
how we can treat and prevent superbugs from taking over the world…..
Thanks
for reading!
Julie S. Paschold
4-12-2019