Crop Advisor’s Casebook – for Oct. 18, 2010

This is the first instalment of the Crop Advisor’s Casebook. Each issue, we’ll present a specific problem a farmer had. We’ll give you all the information you need to determine just what caused the specific problem. Let us know your solution and we’ll send you a hat and a subscription to the magazine (see details below).

Last June, a Manitoba farmer was surprised to find bare patches in his flax field while doing his routine scout. John farms 2,500 acres of canola, flax, barley and wheat southwest of Shoal Lake. He thought the amount of precipitation his fields had seen that spring might be the problem.

“It’s been really wet lately and I think over-saturation has caused my seed to rot,” he explained over the telephone.

The next day, out in John’s field of flax I saw large, irregular, bare patches surrounded by emerged, healthy plants approximately five centimetres tall. These bald spots were found mainly on hilltops and drier areas.

When encountering a spotty field like this one, there are many factors to consider when seeking out a cause for the destruction. Initially I had to consider issues ranging from the weather to disease. Excessive rain, damage due to hail or frost, John’s fertilizer application rate, poor germination, seeding depth as well as pests all had to be eliminated as potential causes for the disappointing flax crop. Was his seed rotten, were John’s fertilizer rates correct or had his fertilizer burned the seed, had he seeded too deep and the flax hadn’t emerged yet, was there something wrong with the seed lot, or were pests killing his plants? All of these questions needed to be answered.

We did some checking, and damage due to frost and hail was not the issue because weather reports were good for that time period and the bald patches were surrounded by healthy plants. In order to determine if the problem was due to excessive moisture in the soil and rotting seed we’d have to check the seed in the ground for our answers.

We dug around in the soil to check germination rate and seeding depth. We found empty seed coats in the rows as well as flax seedlings, so poor germination due to rotting seed was not responsible for the bare patches. The evidence of germinated seedlings also put to rest the theory the flax was seeded very deep and hadn’t emerged yet.

Next we confirmed John had used the correct application rate by looking at his fertilizer records, so the fertilizer had not been toxic to the seed. There were no signs of disease on the emerged and growing flax plants. All of this evidence together made me suspect we were dealing with some kind of pest.

We went back to the flax seedlings and studied them closer. Upon examination we found they were chewed off. But chewed off by what?

What is killing John’s flax plants, leaving his field with big bare patches? Send your diagnosis to Crop Advisor’s Casebook, Box 9800, Winnipeg, MB, R3C 3K7; email [email protected]; or fax 1-866-835-8467 c/o Lyndsey Smith. Best suggestions will be pooled and one winner will be drawn for a chance to win aGrainewscap and a one-year subscription to the magazine. The correct answer, along with the reasoning which solved the mystery, will appear in the next Crop Advisor’s Solution File in the November issue ofGrainews.





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