MEDICINE HAT, Alta. – Sometimes it’s difficult to tell if crop damage has been caused by herbicides or disease, especially for producers growing a crop that is new to them.
If the damage has been caused by fungus, treatment is limited.
Ron Howard of Alberta Agriculture’s Crop Development Centre at Brooks, advises producers to conduct regular field checks and find a good plant reference book to help, such as Diseases of Field Crops in Canada.
“By the time you see a high level of disease in your crop, it is too late to do anything,” he said at the Southern Alberta Conservation Association annual convention Dec. 2.
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“If it is too far gone, sometimes you just have to leave it. It would be too costly or ineffective to try and control the disease.”
Weather conditions are a prime contributor to plant disease and 2008 was a challenging year. A cool, dry spring and wet June delayed plant development. Harvest was two weeks late, yet in the end the quality and yield of many dryland and irrigated crops were average to above average.
Still, there were key diseases reported.
Net blotch in barley, a fungal leaf disease spread by air borne spores, causes a net-like pattern on the leaves. The fungus consumes the leaves and it moves up the flag leaf causing damage that can be severe up to the kernels.
Tan spot on barley or yellow leaf spot on wheat, another fungus, creates a yellow halo around brown spots on the leaves. It thrives in warm, humid conditions and spores are air borne.
Stripe rust was also reported. Spores blow into Alberta and Saskatchewan on prevailing winds from as far away as the American Pacific Northwest.
It was seen on soft white winter wheat and can affect barley. It causes yellow and brown stripes on leaves and can affect blooms and shrink kernels. Stripe rust is hard to control but usually spores die during winter. It’s a fast moving disease but a foliar fungicide can be applied to control it.
Ergot was found in wheat, rye and triticale. It replaces the kernels with a dark coloured fungus. Yield is reduced because of formation in the head. Grain containing ergot can be toxic to livestock.
About 10 percent of southern Alberta’s red spring wheat crop was downgraded because of it. No fungicide is available, forcing farmers to rotate crops.
Fusarium graminearum on wheat and barley has been found in southeastern Alberta, especially on a few plots of irrigated durum. It attacks many parts of the plant and a more aggressive form seems to be appearing.
“This year fusarium head blight was a little more severe because of the weather we had around flowering time,” Howard said.
Stem rot on canola appeared in some central Alberta fields this year. Producers noticing the disease should not replant canola on the same fields next year. It causes a black spot on the canola stem and destroys the photosynthetic part of the plant.
Clubroot remains confined to Alberta, but more cases are appearing in the Edmonton region. Cases from the Peace River region are being retested because of false positive results.
Sanitation of equipment and clothes is the best prevention method. Machinery should be power washed with a light disinfectant that stays on the equipment for 10 to 15 minutes to kill the spores. The length of crop rotations depends on the degree of infection.
For heavily infected fields, canola may have to stay out for six to eight years.
In addition, peas were affected with ascochyta blight this year. It causes lesions on leaves that produce sticky spores. It affects the pods and will grow through the wall and infect the seeds. If the seeds are reused, the cycle of infection continues into next year’s crop.
“This disease has been a very significant trial to the chickpea industry. It has been a major deciding factor for producers getting out of chickpeas because they just can’t manage it,” Howard said.
Downy mildew on field peas was reported. However, yields were good because proper timing of fungicide use and hot, dry weather stopped its progress.
