By Faye Bouchard PAg, MSc, Crop Protection Laboratory Manager
So far we have seen a higher volume of samples at the Crop Protection Laboratory in 2016 compared to 2015. However, we have received less than half as many samples in July as we did in June. Our most common submission in July continues to be pulse crops with root rot (14 samples from July 1 to 22) but the number of samples with suspected herbicide damage have tapered off (six samples from July 1 to 22). Overall, the primary issues diagnosed for most of the samples from April 1 to July 22 have been either suspected herbicide damage (59 samples), root rot (59 samples) or environmental stress (24 samples).
Our total number of samples testing positive for Wheat Streak Mosaic Virus (WSMV) is now up to nine, and we have had some inquiries regarding Fusarium Head Blight (FHB) symptoms showing up even when crops were sprayed with fungicide (note that even perfectly timed fungicide applications will only help with suppression of FHB under high disease pressure and humid conditions). So far we have had one barley sample diagnosed with FHB (Photo 1). We are also starting to receive samples for the FHB survey, which will keep us busy into the fall, along with the clubroot survey and preparations for Herbicide Resistance testing.
Herbicide Damage vs Aster Yellows in Flax
We do not test for presence of phytoplasma at the CPL; however, similar to our herbicide injury diagnoses, we base our diagnosis on symptomology and field history provided in diagnostic forms. We have had six flax samples diagnosed with suspected herbicide damage, consistent with either Group 2 or Group 9 injury (it is difficult to tell symptoms apart, but with field history we may be able to say it is one or the other). Symptoms for Group 2 and Group 9 damage include yellowing and branching at the nodes.
The sample shown in the middle was diagnosed with Aster Yellows after some debate (Photo 2). Symptoms were consistent with Aster Yellows (leaf-like flowers and yellowing), although they were not as obvious as the Aster Yellows symptoms (image on left) brought into the lab by our Plant Disease Specialist. For the sample shown in the middle, without additional information regarding what was sprayed in this or its neighbouring field(s), it would be difficult to diagnose or rule out herbicide damage. However, samples showing the malformation of flowers due to Aster Yellows is striking.
| Aster Yellows in Flax (left and middle) vs suspected herbicide damage from Group 2 and/or 9 in flax (right).