Monday, April 16, 2012

Glyphosate herbicide injury

Glyphosate (various trade names) is a commonly-used herbicide for controlling weeds in blueberry plantings.  This product is safe and effective if used according to the label, but can cause injury to blueberry plants if allowed to contact green stems or leaves. Glyphosate injury from applications made in 2011 is now visible in some fields.  On blueberry (and many other woody plants) this herbicide can cause short, stunted shoots and strap-shaped leaves.  Again, the injury you are seeing now in spring 2012 is from applications made last season (2011), where individual shoots were accidentally hit by the spray solution.  The photo below shows blueberry stems with developing fruit, comparing normal (left) vs glyphosate-injured shoots (right).

Injury can occur on a single stem or on the whole plant, depending on what part of the bush was hit with the spray solution.  Though not a soil-active herbicide, it is possible (through misuse) to cause symptoms over the entire plant if the concentrated spray solution is allowed to soak into the ground and saturate blueberry roots,  so be sure to mix correctly, use sparingly, and only apply to the plants (weeds) you wish to control!  Do not spray so heavily that the product soaks into the ground around the blueberry roots. Wetting bare, weed-free soil serves no purpose since glyphosate has no soil activity and will only control the weeds that are contacted by the spray solution.  As always, read and follow the product label.

Glyphosate injury (left) compared to a normal shoot (right)