One of the rituals of autumn in Fond du Lac County is the onslaught of geese that either invade or grace the landscape, depending on your point of view.  One thing is for sure....geese are smart animals.  Just the fact that they fly in a “V” pattern instead of the more complicated “G” formation lends some credence to advanced cranial activity.  They also quickly determine safe refuges in which to feed, swim, and socialize.  Further, they remember these same vacation spots from year to year.

     On many planted winter wheat fields, geese fall into the pest category.  A flock can pull thousands of young wheat seedlings out of the soil in a short period of time.  One plan of attack to prevent such cereal killings is to use propane powered field cannons, which are timed to go off at preset intervals and mimic the sound of a gun.  During the first week of use, the cannons are extremely effective.  By the second week, the geese become more accustomed to the periodic blasts (and probably have documented a zero casualty rate).  It’s usually sometime during the third week of use when the geese start refilling the propane tanks for the landowner.

     The point here is that familiarity doesn’t always breed contempt.  Sometimes it breeds ineffectiveness.  Such is often the case with goose control measures and it’s also the case with weed control.  In recent years, the cannon of choice to kill weeds in corn and soybean fields has evolved to a single chemical.....glyphosate, the active ingredient in RoundUp and a number of other herbicide products.  The glyphosate resistant plant gene has become as much standard equipment in corn and soybean seeds as electric door locks are on a Ford or Chevy.  Both options make the user’s life a bit easier and all of us are usually willing to pay for convenience.           

     Nature’s mechanism for combating a single bullet approach to weed control is very simple....there’s power in numbers.  For every weed species, there is some individual out there with genetic resistance to a herbicide active ingredient that otherwise is responsible for killing 99.99... percent of the remaining population.  With this in mind, common sense dictates the actual chance of finding and perpetuating resistant plants increases as more weeds are sprayed with glyphosate.  For example, spraying a trillion weeds results in a higher chance of finding a resistant weed than spraying a million weeds.

     Following this line of thinking, the risk of resistance can be decreased by either reducing glyphosate use, reducing the number of weeds sprayed, or both.  There have been no recent signs that glyphosate use is on the decline; however, such a scenario is possible if glyphosate weed control programs become more costly than alternatives or if a similarly priced alternative equals the convenience of glyphosate.

     Reducing the number of weeds sprayed is the other approach to lowering the risk of glyphosate resistance.  This is best accomplished by using multiple herbicide modes-of-action with overlapping weed spectrums in rotation, sequences, or mixtures.  In other words, using other herbicides instead of glyphosate or with glyphosate.  Of course cultural practices that reduce weed populations such as tillage, cultivation, and crop rotation also need to be incorporated.