Crop advisor casebook: Bare patches in lentil crop puzzles Sask. grower

A Crop Advisor's Solution from the April 7, 2020 issue of Grainews

Jodi Christopher. photo: Supplied

Back in early June, I was out scouting fields near Main Centre, Sask., when I came across a problem on one grower’s farm. A field containing lentils had several large bare patches, so I called John, the farm owner, to let him know what I’d found.

John, who also grows durum wheat and canola on his 12,000 acres, was in the area and hurried over to have a look for himself. When he saw the bare patches, John wondered aloud if herbicide injury or carryover, or perhaps wind damage, was responsible.

As we entered the field to have a closer look, I asked John for details about his weed control program, but he didn’t reveal anything that could have caused a problem like this.

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The herbicide he’d applied to last year’s wheat crop, for instance, shouldn’t have resided in the soil until now, and the label for the post-harvest herbicide application from the previous fall indicated it was safe to re-crop into lentils.

In addition, the lentils across the rest of the field were now at the eight-leaf stage and didn’t exhibit any signs of herbicide injury, and there was no trace of linear lines in the crop, which could have suggested sprayer damage.

Wind damage couldn’t explain the symptoms either, since there hadn’t been any unusually high winds reported in the area lately. Also, the worst-hit areas were in low-lying regions of the field, which made wind an unlikely culprit.

It had been a fairly dry spring, so I decided to do some digging in one of the bare patches to see if it was a seed germination issue. It didn’t take long for me to determine it wasn’t that but something else entirely causing the problem.

Crop Advisor’s Solution: Cutworms create bare patches in lentil field

I discounted my seed germination theory when we dug up some soil in one of the bare patches and discovered rows of plants that had healthy roots and stems but were cut off just above the soil surface.

We also found cutworms in the soil, so I knew we’d found our culprit.

The above-ground portion of the plants had been consumed by the pests, which were still actively feeding. The cutworms’ feeding areas were also getting larger, so I urged John to spot spray the unaffected areas in the field with insecticide that evening to protect the rest of his lentil crop.

The insecticide application worked to prevent further cutworm feeding and crop loss in the field. However, the bare areas in the field didn’t produce any crop that year and did end up with a thriving weed population, which needed to be addressed prior to harvest.

John now knows that any areas of a field with missing plants, even small patches, may be worth investigating to see if there is a pest issue. To prevent a similar situation in the future, I recommended that John scout his lentil fields diligently during the early growth stages of the crop, so if there were problem areas, they’d be spotted and could be addressed sooner. I also suggested satellite imagery may also help with efficient scouting for spotty problem areas across his acres.

Jodi Christopher, PAg, CCA, works for Richardson Pioneer Ltd. in Herbert, Sask.

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