By: Faye Dokken-Bouchard, PAg, Manager, Crop Protection Lab
By this time last year, more than 200 samples had been submitted to the Crop Protection Lab, whereas this year we have received less than 100 samples so far. While environmental stress and suspected herbicide damage continue to be the most common diagnoses, the major differences are the type of stress (dry vs wet) and the number of root rot samples.
As of July 11 last year, we had diagnosed more than 50 samples with root rot, while this year only four samples have received that diagnosis. This makes sense, considering that excess moisture contributes to root rot infection. The type of environmental stress diagnosed last year was also often related to excess moisture, whereas this year lack of moisture and wind damage have played more of a role.
Suspected herbicide damage has been diagnosed in 12 samples so far; however, we cannot definitively confirm herbicide damage and do not test for presence of chemicals at the lab. Diagnoses are made based on symptomology and the field history provided in diagnostic forms.
As part of the Dutch Elm Disease (DED) testing program, we have also had seven elm tree samples positive for DED, out of a total of 40 samples tested.
Always remember to completely fill out the field history when submitting a sample for diagnosis, including previous years’ herbicide applications, and the sprayer history, including what was in the tank prior to any applications in the field. We can provide a diagnosis that supports the suspicion of herbicide damage in cases where symptoms are consistent with a particular herbicide group, along with evidence from the field and/or sprayer history of possible residue, tank contamination or drift.