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Crop Advisor’s Solution – for Nov. 7, 2011

Last July, Bob, a farmer from south of Yorkton, Sask., called me about the patches of browning and dead spring wheat plants he noticed appearing in one of his fields. Bob is strictly a grain producer who farms 5,500 acres of spring wheat and canola. As one of my agronomy clients, Bob and I scout his fields together every seven to 10 days.

Up until the beginning of July, Bob s wheat crop had been progressing well. But by the second week of that month he noticed randomly situated, irregular-shaped patches of dying wheat developing on the hilltops in one of his fields of rolling, hummocky-ridged land. I think it s damage from a chemical, he told me, because he d noticed the symptoms seven days after spraying.

Bob and I thoroughly scouted the field when I arrived at his farm. In the affected areas, I noticed the wheat had grown to the three-to four-leaf stage before withering and dying. No other plants were growing in the patches.

When we discussed the details of this crop, I noted that Bob had done many things right. He had used high-quality, certified seed, his seeding rate and depth were correct, and his fertilizer and herbicide application rates and procedures were also accurate. After consulting Bob s records, I determined that herbicide carryover was also not an issue.

Germination was not an issue because the number of dead plants in the patches indicated the germination rate had been excellent, with a plant stand population of 40 or more plants per square foot. When we checked for insects, such as cutworms and wireworms, none could be found at the soil s surface or slightly below ground.

I asked Bob to tell me about any differences, no matter how insignificant they may seem to him, in the treatment of this field to that of his other fields.

No differences, he said. But I guess this is the only field where we didn t apply a seed treatment.

There it was the answer. I pulled up some plants from the affected areas, and as soon as I saw the dried up, dead coleoptile and root material I knew we were dealing with root rot, a general term for a group of plant diseases caused by fungal or oomycete infection.

Laboratory results from plant samples confirmed that root rot was the cause of the patches of dying wheat in Bob s field, although lab analysis could not specify, with certainty, the type of root rot involved.

Because the wheat seed planted in Bob s other fields had been treated with a fungicide, only the field with untreated seed had developed the disease. Generally, the use of high-quality, certified seed, seed treatments and shallow seeding depths, as well as ensuring adequate phosphate fertility will increase your success rate in the prevention of root rot.

Sadly, nothing could be done to solve or reverse the areas affected by root rot in Bob s field this year. The silver lining in this case is Bob now knows that a seed treatment is an important part of establishing and growing a healthy, productive crop, and next year, we can prevent this problem from reoccurring.




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