Paul, who farms 3,500 acres north of Camrose, Alta., was convinced cutworms were taking a bite out of his canola crop. It was mid-June last year when he noticed his canola plant stand was thin. Also, many seagulls were circling the field. He thought cutworms were attracting the birds, as well as damaging his crop and causing the decreased plant density. He asked me if I would visit his farm to confirm cutworm pressure.
From the road, although there was still lots of green in the field, some areas were patchy where the plant stand was thin. In other spots, entire rows were missing plants. However, there was no obvious pattern to the patchy areas or missing rows.
Upon entering the field, I noticed the soil was saturated. Paul’s fields received about an inch of rain the night before and almost five inches during the previous 10 days. In fact, this area experienced high precipitation levels last fall, continuing into the spring.
In Paul’s field, I noticed what looked like poor germination in some areas, while other spots had heavy weed pressure. The canola plants ranged in development from cotyledon to the two-leaf stage.
I told Paul I didn’t think we were dealing with a cutworm issue as there were a few factors ruling this type of pressure out. To begin with, cutworms favour warm, dry, light-textured soils, like those found on hilltops or south-facing slopes, not the saturated soils in Paul’s field.
And although cutworms create bare patches by consuming all the plants in an area, moving outwards to feed on more plants, the patches in Paul’s field didn’t have any other evidence to support cutworm feeding.
For example, cutworms cut and sever plant stems below the soil surface. Cutworm damaged plants often look wilted, tipped over, or dead. We didn’t find any severed stems or tipped over, wilted, or dead plants. There would also be chewing damage, such as holes or notches in the leaves, not to mention the presence of cutworms in the soil. When we dug in the rows we didn’t find any cutworms; however, we did find plenty of earthworms.
“That explains the seagulls circling overhead,” I said.
“This field had flea beetle pressure earlier this spring,” said Paul. “Did that feeding damage cause the thin stand?”
It was a good guess, but it was only part of the answer.
Crop Advisor’s Solution: Flea beetles and excess moisture cause thin canola stand
Part of the issue was flea beetle stem feeding in the spring. Paul chose the base seed treatment for his canola seed, which didn’t include extended flea beetle control. At that time, some of the canola plants died because of the flea beetle feeding, while others looked unhealthy, and were set back developmentally.
Another big factor affecting this canola crop was excess moisture.
In the fall of 2016, the Camrose area experienced high levels of precipitation. Those wet conditions persisted the following spring, making it hard for producers, like Paul, to get into their fields and seed into good conditions. The excess moisture and saturated fields forced producers to seed around water and through low-lying areas, which were very wet.
In fact, the night before I visited Paul’s farm, the field in question received an inch of rain and almost five inches during the previous 10 days. The plant stand was thin and patchy, and in some areas, entire rows of plants were missing; however, there was no obvious pattern to the damage. The canola plants ranged in development from cotyledon to the two-leaf stage. There was also heavy weed pressure in some areas.
After scouting the damaged field, we discussed Paul’s spring seeding operations and scouted a few other fields. Paul told me because he was seeding into saturated soil, he was unable to maintain an even seeding depth. He said his drill was set as high as possible, but it was still too deep. The wet conditions made it near impossible to seed properly, resulting in poor germination.
After seeding, the temperatures remained cool, and the field received high levels of precipitation, also slowing growth and stressing the crop.
There is nothing growers can do about inclement weather other than delay seeding until the field dries up, but that wasn’t going to happen in Paul’s case. However, the canola plants in this field did eventually grow through the stress. The plant stand became even in most areas, with only the odd spot looking thin.
Joelle Burnstad works for Richardson Pioneer Ltd. in Legacy Junction, Alta.