I’m certain it’s flea beetles,” said Dave, an Alberta producer I visited last June after he discovered his canola crop had emerged poorly.
While some areas of the crop were coming up well, others had no germination or uneven emergence, as well as spots with stunted plant growth. Also, regions with lighter soils, such as hilltops, were more affected.
Dave’s 2,500-acre farm is located near Carseland, Alta. Because Dave thought the patchy emergence was a result of flea beetle feeding, we scouted his field in the afternoon heat, when we stood the best chance of finding the pests.
We did find adult flea beetles, although only minimal chewing on cotyledons, first true leaves and stems had occurred. In my opinion, the chewing damage was not extensive enough for it to be the cause of the emergence issues.
Even the areas with the lowest germination rates and highest numbers of stunted plants, such as the hilltops, had minimal chewing damage, and couldn’t be responsible for the emergence and plant growth problems in this field.
Seedling death can also be caused by fertilizer burn. When I dug into the soil, I found some fertilizer prills that hadn’t broken down due to inadequate moisture levels. These fertilizer prills were found at a safe distance from the seed. Thus, fertilizer burn didn’t cause the germination issues.
I continued to dig in the soil along the seed row and I found more canola seed that hadn’t germinated. Additionally, I found a higher number of ungerminated seeds on the hilltops, after digging in these lighter soils.
We ruled out seeding issues, as the seeder settings were correct and the machinery was working properly. Also, I checked seeding depth in the seed row, which was also correct.
However, the intact fertilizer prills, high number of ungerminated seeds on the hilltops and stunted plants were pointing to the problem’s answer in this field.
Crop Advisor’s Solution: Poor soil moisture
Last year, the growing season started with sufficient precipitation, and producers seeded into adequate soil moisture. However, as often happens in this region, the environmental and soil moisture conditions changed rapidly. The area received little precipitation after seeding and the soil dried up; thus, some of the canola seeds couldn’t germinate because of the inadequate moisture levels.
For example, the germination rate in areas of the canola field with lighter soils, such as the hilltops, was much lower than slopes or low-lying regions, where the soil held onto moisture longer, allowing normal germination and plant development.
Other clues that led me to this diagnosis were the presence of fertilizer prills in the seed row, which require adequate moisture to break down, as well as the stunted plant growth caused by water stress.
In addition, after finding ungerminated seeds in the soil, I had to dig down another few inches to access soil with enough moisture for germination.
In this case, Dave seeded the canola at the correct depth and into adequate moisture. Because he couldn’t have predicted the swift change in environmental and soil conditions, there was no way he could’ve avoided this situation.
However, if soil moisture is limited at planting, choosing crops that can be seeded at greater depths than canola, such as the cereals durum, wheat and barley, is another option.
Early in the growing season, Dave’s canola crop showed evidence of flea beetle feeding. We continued to monitor the crop for flea beetle feeding because Dave wanted to save as much yield as possible. However, flea beetle populations remained well below threshold levels and feeding damage was negligible and didn’t affect yield.
The region did receive small precipitation amounts as the growing season progressed. And except for a few hilltop areas, overall, the canola crop’s yield was substantial considering the drought conditions experienced earlier in the season.
Jarrod Fogal works for Richardson Pioneer Ltd. in Carseland, Alta.