Pink may be a nice colour, but it has no business in a healthy field of wheat. Jason, a farmer who grows 5,000 acres of wheat, canola, oats and barley west of Swan River, Man., called me last August after he noticed some of his wheat heads were salmon-coloured. Also, some heads were white and weren’t filling properly. Jason thought the wet, humid conditions had something to do with these symptoms. At first he thought the problem was root rot, but he ruled that possibility out himself since the roots looked healthy. He asked me if the problem could be the new variety he’d seeded because the worst of the damage was located on a half section planted with this variety, while his other fields, planted with a variety he’d often used in the past, showed little sign of disease. He said he’d picked the new variety for its higher yield rating.
Standing at the edge of Jason’s field, I noticed one side of the half section looked twice as diseased when compared to the other. On that side, 10 to 15 per cent of the wheat heads showed the symptoms he’d described over the phone. Jason told me that side had been seeded on wheat and the other healthier side had been seeded on canola stubble. His other fields of wheat were faring better — they showed the least incidence of infection, only a very small percentage of the wheat heads had been affected.
I knew at first glance — at the pinkish wheat heads — what the problem was in Jason’s fields. To confirm my suspicion, I asked Jason about the field’s history. The fertilizer application rates and seed treatments used in this field were the same as Jason’s other wheat fields, and all fields had been seeded within the same week. Jason applied fungicide at the flag leaf stage to control leaf diseases. Weather conditions had been humid and warm for that growing period. These environmental conditions, the wheat on wheat rotation, as well as Jason’s introduction of a new variety combined to create a perfect storm for an infestation of fusarium head blight.
Fusarium head blight is a fungal disease most often caused by the species Fusarium graminearum, F. culmorum and F. avenaceum. The disease reduces yield and grade in wheat, and produces toxins that can be harmful to humans and livestock. The white wheat heads are caused by premature bleaching of the infected spikelets. Also, during wet conditions infected heads may appear whitish or pinkish due to fungal growth on the heads. As a result of the formation of spore-bearing structures called sporodochia at the base of the glumes, wheat heads may also appear orange or salmoncoloured.
FHB is relatively new to the region. For the past year or two it has been showing up in areas east of Swan River. The new variety Jason planted had a higher yield rating than the variety he used to seed his other fields, but it also had a lower rating for resistance to FHB. The wheat on wheat rotation also made the environment more favourable to FHB, explaining why the side seeded on canola fared better. A three-to four-year rotation is ideal when trying to prevent FHB. I also recommend producers try to avoid growing wheat from seed that may have been infected with FHB.
Be on the lookout for FHB when weather conditions are humid and warm, especially five to 10 days before head emergence. Jason sprayed a fungicide at the flag leaf stage to control leaf diseases but that did not help prevent FHB. Producers see the best results when applying fungicide at the onset of flowering.
Growing wheat varieties with a high rating for resistance to FHB, in combination with the application of a fungicide and seed treatment, results in lower levels of FHB in the field.
The cost to Jason was quality and yield. He lost approximately five bushels per acre. But, he’d only seeded one-quarter of his wheat fields with this variety and he was able to blend it with his other wheat to maintain a better grade. Remember to scout your fields often for signs of FHB when conditions are favourable for the fungus to grow and spread.