Chemical Resistance Part One: How?

 

Chemical Resistance Part One: HOW?

 

When you have a cough, the sniffles, a fever, or just plain feel awful for a long enough amount of time, chances are you’ll be headed to the doctor’s office.  Your doctor may prescribe antibiotics to kill the “germs” causing your symptoms.  Recently, there has been increasing attention brought toward antibiotic resistant germs, or bacteria who aren’t killed by the chemical in the drug anymore.  So even if you take the medicine, you stay sick!  The bacteria has become resistant to the chemical. 

 

How does an illness that you have relate to agronomy?  Well, the same thing is happening to our crops.  A plant can get a disease, too.  And a “germ”, be it a bacteria or other critter, that attacks humans isn’t all that different from critters that attack plants.  There are three basic areas I think of when it comes to chemical resistance in crops.  They relate to three kinds of chemicals or pesticides we use to “treat” or kill pests that ruin our fields. 

•          Diseases, which many times are fungi and killed by fungicides
•          Insects, killed by insecticides
•          Weeds, killed by herbicides

 

There’s more information regarding chemical resistance than I could go into even if I wrote every week for a year, but I want to go over HOW a critter can become resistant to something that used to kill its predecessors.  When you get sick, there are different kinds of critters that could be causing your illness.  There are bacteria and viruses.  Similarly, a plant can get “sick” from a bacteria or fungus.  There are many different kinds of weeds—in fact, ANY kind of plant can be a weed if it’s growing somewhere we don’t want it!  Different kinds of insects each plants.  All of this diversity is great—but when we use the chemicals wrong, they can seem to gang up on us. 

 

We know that, in science, nothing is 100%.  That includes chemicals designed to kill critters that cause damage.  When a disease causes problems, it’s because there are too many critters living on the plant that it can’t fight off or tolerate all of them using it for a resource.  A drug or pesticide is designed to kill most of the disease, so the plant (or host) can live on. 

 

Imagine a diseased area with lots of fungi “critters” on it:

 

After being treated with fungicide, most of the critters die, leaving only a few left:

 

You’ve heard the phrase, “What doesn’t kill you makes you stronger”?  That’s true here!  The remaining critters that survived the treatment “remember” that chemical, and pass this “memory” on to many of its next generation.  The next time that fungus gets out of control…

 

 

….and we treat it with the same fungicide, more critters survive because their genetics “remembered” how to do it from last time. 

 

If this happens too many times, we have critters that become resistant to the drug or chemical, so it doesn’t work to kill them anymore. 

They are superbugs!!!

 

 

In a way, we’ve created our own problem. 

 

Stay tuned for next time:

Chemical Resistance, Part Two: WHY?

 

Thanks for reading!

Julie S. Paschold

2-28-2019

Soil v Dirt

I didn’t begin my University education in the University of Nebraska-Lincoln’s College of Agricultural Sciences and Natural Resources.  I was pre-med.  I loved biology.  But as I looked down the long road of required coursework in order to earn my M.D. and realized how much blood I might have to be dealing with (I really don’t enjoy blood), I hesitated.  My dad, who graduated from UNL with his B.S. in Agronomy in 1972, suggested that I take an agronomy course.  Agronomy is also called crop science, which is like applied botany, and botany is like applied biology, so I said “sure”.  Dr. Rick Waldren was my first Agronomy professor (I still have the bright green covered, wire-bound textbook!).  He liked his job, and it showed.  He made learning about epicotyls and glumes kind of fun! 

 

When I decided to change my college major to Agronomy, I soon found a job working as an undergraduate research assistant for the soil fertility project at UNL.  On my first day, Dr. Dan Walters, my new boss, asked me an important question.  He said in order to work for him, I needed to know the answer.  His question:

 

“What is the difference between soil and dirt?”

 

This wasn’t exactly easily answered.  First, there is a whole branch of science dedicated towards studying the first, and I was just starting in on the classes!  Soil isn’t just the strange stuff that we walk over and build houses on and plant gardens in.  Soil is a whole world unto itself, a living, breathing entity; an ecosystem with minerals, air, water, and more living creatures than you or I could count.  Plants don’t just use soil to grow their roots into in order to anchor themselves from blowing or washing away.  Roots “drink” the water, “breathe” the air, and uptake nutrients that the plants need to grow and live.  Think of them as hairy, fingerlike straws.  Living on these roots and in the tiny air holes and water bubbles are living creatures—bacteria and fungi and other tiny organisms that co-exist with the “bottom half” of those green things that stick out of the ground.  Intricate chemical and biological processes take place.  So complicated, in fact, that scientists have given “soil” a science of its own.  Soil is its own little world.

 

To the average person, there is no difference between soil and dirt.  The words are used interchangeably.  So when Dr. Dan asked me the difference, I was stumped.  Was this a trick question?  WAS there a difference? 

He smiled, and, after requesting that I purchase a pair of steel toe Red Wings from the store in Havelock for our field work, he explained. 

 

Soil is indeed a complicated substance, something I spent the next seven years learning about….and just “scratched the surface”, so to say. 

 

But dirt?  Dirt is that junk under your fingernails and between your toes.  Dirt is what is stuck on your shoes and gets tracked in on the floors and scatters on your furniture.  Dirt is the reason you jump in the shower and pull out the cleaning supplies.  In other words, dirt is determined by “location, location, location”.  The answer was simple after all.  Dirt is soil where you don’t want it. 

My first Agronomy textbook, from “Agronomy 101” at UNL in 1995.