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Crop advisor casebook: Zebra stripes in barley a result of herbicide carryover?

A Crop Advisor's Solution from the November 5, 2019 issue of Grainews

Charisse Garland. photo: Supplied

Ken was driving by one of his barley fields at the end of May when he spotted a problem. His emerging barley crop seemed to be turning yellow, and when Ken pulled over to have a closer look, he was alarmed by yellow bands resembling “zebra stripes” on many of the plants.

Ken, who also grows durum wheat, canola, yellow peas and green lentils on his 2,700-acre farm near Swift Current, Sask., called me soon afterwards to see if I could help figure out what was wrong with his barley.

“I’ve heard some other farmers around here have had issues with herbicide carryover from last year,” he said. “I’ve talked to someone who thinks this is what’s going in my field, but I thought I should get a second opinion.”

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When I arrived at Ken’s farm, I found the barley field just as he described. The banding could be found throughout the field, although the worst of the symptoms occurred in the higher areas of the field. The symptoms were less severe on the low-lying land. Most of the plants were only in the one-leaf stage, but the yellow horizontal stripes were clearly evident on the recently emerged crop.

At first, I suspected a nutrient deficiency might be to blame, but there was no indication of that when I looked over Ken’s soil sample reports. As well, the horizontal stripes on the leaves were not consistent with the typical chlorosis induced by a lack of nutrients. The yellow stripes on the plants were not running along the length of the leaves, as would have been the case with a nutrient deficiency, but along their width instead.

There were yellow bands resembling “zebra stripes” on many of Ken’s barley plants. photo: Supplied

Ken’s initial thought — that herbicide carryover from the previous year’s pea crop might be to blame — didn’t look to be the culprit either as the horizontal leaf banding was also inconsistent with herbicide carryover symptomology. A review of Ken’s herbicide usage records from the previous four years also revealed there hadn’t been any soil active herbicides applied that would have caused any crop injury.

I also considered the plant symptoms I was seeing could have something to do with improper seeding or an issue with fertilizer placement. Upon digging in the seed row, I observed the seeds were consistently placed at a depth of two inches and I also didn’t find any injured seedlings, suggesting seeding depth and fertilizer burn were not contributing to the banding in the crop.

At this point, I started to think back about some other times I’d seen this kind of banding in barley, and the role growing conditions might have played. Could this be the answer to the puzzling zebra stripes in Ken’s barley crop?

Crop Advisor’s Solution: Banding in barley caused by early season temperature shifts

I had seen similar symptoms in a barley crop a few times before, and when Ken and I started talking about what kind of growing conditions there had been in those cases, the answer to Ken’s zebra stripe puzzle became much clearer.

I was aware environmental conditions could cause this type of yellow banding in emerging barley plants, and a look at the area’s weather station reports from recent weeks confirmed this was what had happened with Ken’s crop.

In the week between first emergence and when Ken initially noticed the plant symptoms, there had been dramatic shifts in temperature, with daytime highs ranging from 27 to 31 C and nighttime temperatures dropping as low as 2 C. Small seedlings can be sensitive to large temperature shifts, which can result in chlorosis and the eventual necrosis of the leaf at the soil surface.

It was environmental conditions, therefore, that had caused the injury in the barley plants, and there wasn’t anything that could be done to remediate the crop injury.

Looking back, Ken probably could not have prevented the crop injury without experiencing other adverse environmental conditions. If he had seeded his field a week earlier, there was a frost event that would likely have damaged the emerging barley plants more significantly than the temperature banding.

Conversely, if Ken had waited and seeded later than he did, the depleted soil moisture may have influenced crop emergence. All this illustrates just how hard it is sometimes to plan your seeding decisions around the weather.

Fortunately for Ken, temperature banding is typically cosmetic and rarely causes yield loss. Because it was so early in the season, his barley had time to bounce back and there was little to no effect on the crop’s growth or yield.

Charisse Garland works for Richardson Pioneer Ltd. in Swift Current, Sask.

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