Too Much of a Good Thing

We were away on a family holiday the last 10 days of June and upon returning I noticed some patterns in quite a few food grade soybean fields.  The picture below is one such pattern.

This is another.

Obviously something to do with a sprayer.  This field was spot sprayed with a post emergence herbicide the last week of June cleaning up broadleaf escapes.  There were entire fields in the area that looked like the beans on the right of the picture.  If we look closer, the reason for the injury is clear.

This is text book example of Group 2 herbicide injury caused by being too aggressive with this family of herbicides.  Group 2 products in soybeans include Pursuit, First Rate, Classic and Pinnacle.  All fine products that provide good value for money spent.  Unless you use too much, too late.  These fields had Pursuit applied in combination with Boundary and glyphosate at planting time.  By the end of June the soybeans were advancing through the 4-6 trifoliate stage.  An application of Classic or Pinnacle following the Pursuit in an attempt to clean up broadleaf escapes in these big soybeans can lead to this type of injury. The optimal timing for Classic or Pinnacle is the 1-3 trifoliate stage.  This best matches the weed stages with crop safety.  These bean plants will recover, but the purple veins will be seen for a long time.  Yield loss can be dramatic.