Glyphosate: Friend or Foe?

Glyphosate (also commonly known as RoundUp and under other generic labels) is a great tool for controlling weeds where fruit crops are grown.  It takes out both broadleaves and grasses which makes it a popular choice.  However, it can come with downsides.  Weed resistance is one downside.  Another, potentially more devastating problem is misuse, specifically applicator misuse.  I don’t know how many times I have been in an orchard or vineyard that I have seen self-inflicted glyphosate injury on plants.  What makes glyphosate great is that it is non-selective, but that is also what makes it dangerous.  It is indiscriminate when it comes to weed or the fruit plant.  Glyphosate works by inhibiting protein production by stopping the shikimic enzyme pathway.  It is also systemic, meaning that when it is spayed on the leaves of the plant it is translocated back to meristematic tissues (growing points).

What are the results of plant exposure to glyphosate?  Several symptoms such as stunted growth, discoloration (yellowing) of leaves, leaf deformities, and tissue death.  And, oh yeah before I forget, plant death.

Using glyphosate around plants that tend to send up suckers or canes can be tricky.  In the case of brambles, a cane may be several feet away in a row walkway, but it is still coming from the mother plant.  If sprayed it would translocate the glyphosate back through the root system and could harm the mother plant.  I recently saw a case of what I believe to be glyphosate injury in a blueberry field.  See the photo below:

Glyphosate Injury Symptoms in Blueberry

Glyphosate Injury Symptoms in Blueberry

Notice how the leaves are small, yellow, and oddly shaped.  The growth has also been stunted.  Will this cane recover?  Doubtful.  Is the entire plant at risk?  Possibly, but older plants are going to be more tolerant than younger plants unless they are in poor health to begin with.  The lesson here is to be very careful when using glyphosate — don’t apply when it is windy, don’t apply to suckers, don’t apply to exposed roots, and use a spray shield if possible to reduce unintended movement of the chemical to off-target plants.

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