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Things I Did Not Know

August 17, 2012, 11:50 am

I suppose I should have guessed this, but it never occurred to me.  There seems to be a problem with growing weed resistance to herbicides that is entirely parallel to growing antibiotic resistance of certain germs.

Category: Science
  • Mark2

    And the resistance of bugs to pesticides.

    Makes sense in all three cases.

  • MingoV

    The battles against herbicide resistance will be more winnable than those against antibiotic resistance. Crops have an advantage that people lack: crops can be genetically engineered to withstand herbicides that will kill all weeds.

  • Johnathan

    @MingoV: ...so could humans, but it is currently illegal to do figure out how.

  • Dan

    Weeds, like real weeds, not hemp. Man, where am I?

  • Pat

    The weed resistance is nothing more than a selection process of the "fittest". I live in the bread basket where all farmers use some sort of "burn-down", using herbicides - glyphosate (Round-Up TM) being very common. Although most weeds are eradicated right off the bat, over the course of time (several years), it becomes evident that there are strains of weeds which become resistant, and new herbicides (often at stronger concentrations) have to be used to kill the glyphosate resistant weeds. This is similar to what is seen with MRSA (the staphococus resistant germ which is appearing in more and more infected people) in the hospitals. This competition which ocurrs with organisms trying to survive is part of nature. I'm not so sure that the strategy is a "sound one" much like the methods being used by the Fed (and Congress) to deal with the inevitable deleveraging of debt that has to happen. What is interesting, as I'm an old guy, is that every solution appears to have some short commings, and that history is a pretty good evaluator of the solutions tried.

    Regarding the weeds, the chemical "burn-down" had the promise of facilitating "no-till" methods of farming that saved the top soil from erosion, which used to be a huge issue with large scale farming.

  • Bart Hall (Kansas, USA)

    I'm a professional agronomist who farms for a living, or this year attempts to do ... Our current drought is of Dust Bowl severity, but a big reason we don't have Dust Bowl conditions is that Roundup beans permit a much closer planting which does indeed reduce wind erosion. Farmers are also much better at crop residue management than they were even a generation ago.

    That said you can develop weed resistance even to mechanical cultivation. What I mean here is that if you use the very same method of mechanical weed control for many years your weed community will shift towards those species less affected by the cultivation you've chosen. You also militate towards target-species individuals which for one reason or another evade the full effect of the cultivation.

    Just as very few pitchers will stick around the majors for long if all they have is a slider, resistance is not strictly a phenomenon of chemical application -- it is the result of excessively repeating a pest control product or method. That's why you vary your chemicals; vary your cultivation timing and methods; and ideally alternate chemicals with mechanical cultivation.

  • Harry

    Bart,

    You clearly understand the subject better than I, but having been a farmer (eastern dairy farmer where we measure our fields in acres, not sections) your comments make sense. Presently someone else farms our property, renovating some sorry fields previously mismanaged by other disorganized renters, who had let fields be overcome by noxious weeds. For the last couple of years, these fields have been planted with Roundup-Ready soybeans.

    In addition to the elimination (not eradication) of weeds, the soybeans have put nitrogen into the soil, and are beautiful to behold. We got rain this summer, and as of this afternoon the plants are more than four feet high.

    Our plan is to begin rotating some of this, eventually to hay, and some to permanent sod. We will never kill every thistle, but the goal is to make it look like a farm, not a patch of weeds. Maybe some of it will go to corn, then wheat as a nurse crop for clover and alfalfa.

    When I was a kid, my first job on a tractor was mechanically cultivating corn. A few years later, I ran other equipment, including the plow. Had to plow down the manure.

    No doubt weeds will become resistant to our present methods, but we all would be poorer if we had to rely on that cultivator to get the weeds. In North Korea, they cultivate with a slave wielding a shovel.

  • Mark2

    @Bart et al, interestingly with mechanical tilling the weeds do change False flax has changed the shape of its seed so that it mimics the flax seed and is harvested with a winnowing machine that is suppose to be seed selective. Changes by "weeds" by selective pressure to change so their seeds get harvested is called Vavilovian mimicry.

    Sometimes this is beneficial. Rye and Oats came through this type of genetic selection in the harvest of wheat fields. Even false flax which is a problem weed, turns out to have superior oil qualities. There is also a type of Vavilovian mimicry in which plants will imitate insects to encourage the insect to pollinate.

    http://en.wikipedia.org/wiki/Vavilovian_mimicry

  • bob sykes

    Pat is right; it's merely evolution in action. The correct solution is to continually develop new techniques of weed, pest and disease control and phase out the older ones. Given enough time, the organisms will lose their resistance and the older techniques and chemicals can be reintroduced, and they will once again be effective.

    Nothing is permanent. Not even our current civilization.

  • Mark2

    @Bob, I am not sure if old solutions will avail themselves again soon. When all the vegetation without the resistant gene combination get wiped out, all you have left is resistant species. It will take many many more years for new genes to evolve, old plants genes to come back into the pool from far away places, etc. It is almost a one way road.

    On a positive note, mutations to create a resistance do not come for free, plants and animals tend to give up something in return.

    http://en.wikipedia.org/wiki/Rough-skinned_newt

    Rough skinned newts can be eaten by only a certain garter snake, though I couldn't find the research article, the snakes resistance comes at a price. The snake, is much slower than other varieties of garter snake.

  • Bart Hall (Kansas, USA)

    Back when I was a grad student in Alberta studying cereal breeding we made note of the terrible regional problem with wild oats, the seed of which can last over a century in the soil. The preferred control, Avidex, was expensive and losing effectiveness.

    One of the other students piped up "Well then to hell with the tame oats. Wild oats is very high protein and rich in minerals." He went on a few years later to develop a very tasty breakfast cereal from the wild oats, and Alberta farmers growing for that market now have to clean out the tame oats ... which for them is a weed.