Crop Advisor’s Casebook: The secret of the swooping birds

A Crop Advisor's Solution from the April 11, 2017 issue of Grainews

Charisse Garland. photo: Supplied

Last July, Henry, a Saskatchewan farmer, watched as a throng of birds swooped in and out of his durum wheat field. When he scouted the field, he also found some “black bugs,” which prompted him to give me a call.

“You need to look at my durum,” he said. “Birds are swooping, so there must be something in the crop they’re trying to eat.”

Henry farms 2,500 acres of canola, durum and peas southwest of Tompkins, Sask. It was mid-July when he invited me out to his operation to determine what was attracting so many birds to his durum crop.

From the road, the field looked normal. We couldn’t see any abnormal patches or growth. Still, an above-average number of birds were circling and swooping the crop.

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Up close, the wheat plants looked healthy. The crop was completely headed out and around the milky stage, and we didn’t find signs of disease or abnormal growth on the plants’ leaves, stems or heads.

When we checked the crop for insects, we found some mosquitoes and dragonflies, but nothing out of the ordinary, except for a noticeable lady beetle and lady beetle larvae population. Lady beetles are beneficial insects because they prey on other insects that feed on crops — often regulating these pest populations.

Likely, the lady beetle adult and larvae population were the reason birds were circling and swooping the field. But what was attracting the beetles?

I knew farmers in this area, including Henry, harvested hay earlier than average this year because of favourable moisture and growing conditions. That fact, in addition to the presence of the lady beetle population in the field, were two big clues to which pest was making a meal out of Henry’s durum wheat crop.

Crop Advisor’s Solution: Not going to wing it when it comes to pests

Because of the favourable moisture and growing conditions that season, farmers in the area, including Henry, cut hay earlier than normal. Aphid infestations tend to manifest after the first hay cut because the winged adults migrate to new hosts. Producers with cereal crops close to hay flats or near areas where alfalfa is cut should scout their fields frequently for aphid populations.

Since the aphid population in Henry’s crop met the economic threshold (12 to 15 aphids per stem prior to the soft dough stage), he chose to spray the field with insecticide. If a rain event had been forecast for the following day or so, the aphid population may have been suppressed because the rain would have disrupted them.

In addition, because lady beetles and lady beetle larvae are natural predators of aphids, had the aphid population not been so high, the beetles may have been able to curb the pest population, eliminating the need for chemical control.

There is no way to avoid aphid infestations — it’s a matter of pest control when it’s necessary. A week after Henry sprayed the wheat crop, we scouted the field. The aphids were gone, as were the birds, which were after the lady beetle larvae.

At harvest, the crop yield was not affected because Henry sprayed in good time to control the aphid infestation. He felt sure his yield would have been lower if he had not sprayed because his neighbours, who chose not to spray, were disappointed with the yield from their aphid-infested crops.

This was the first time Henry had ever encountered aphids in a durum crop, and he plans to scout for them earlier in the season in future.

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

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