John, a farmer with 2,000 acres northeast of Medicine Hat, Alta., was certain he was dealing with a cutworm infestation.
Last spring, he planted 400 acres of canola for the first time. When the canola plants started to cabbage out in mid-June, John noticed bald spots on hillsides, hilltops and drier areas in his canola field.
I visited John’s farm that evening to investigate the cause of his disappearing canola. His field did appear patchy and the plants were chewed off — only the bottom of the plants remained. Small pieces of stem littered the soil and soil’s surface. We checked the plants adjacent to the affected areas for cutworm larvae, since they sometimes feed on the plant’s leaves but found none. Next, we checked the soil for larvae — they sever plant stems below the soil’s surface — and, again, found nothing. Cutworms were not causing John’s plants to disappear. Also, the plants looked neatly nipped off at the stem. What could be eating John’s canola?
Because the area surrounding Medicine Hat has a significant gopher population, at the beginning of our investigation into John’s disappearing canola I asked him if he had taken measures to control his gopher population that year. He said he had taken care of gopher control early that spring. When we talked about it further, I learned he’d controlled his population only once. He also told me he had noticed only a few gopher holes that spring. It was then that I knew the cause of John’s trouble.
It is true that the best time for gopher control is early in the spring before the foliage is out, but it must be followed up at least two to three times per season, preferably every 10 days to two weeks. If foliage is coming back you know you’ve cleared out the population fairly well.
Just because you only find the odd gopher hole, that doesn’t mean those gophers can’t do a lot of damage, especially in a small field like John’s because there wasn’t a lot of plant population to begin with.
Also, unlike cereals, canola is particularly susceptible to gophers because the growing point is above ground. Once the plant is nipped off it can’t grow back. In the seedling stage, cereals, such as wheat and barley, grow from the crown at soil level, so they can often grow back if gophers are controlled in time.
Gophers are known to be a major problem in this particular region of Alberta. Even a few holes could mean substantial damage. Gophers could present even more of a problem in irrigated fields because of their tendency to move into these fields offering a rich food supply.
Whatever method you choose to control gopher populations — chemical solutions, baits, traps, among others — that method must be followed up until foliage comes back and you are sure the problem has been eliminated.
For John, there was nothing he could do about those destroyed acres of canola, but he was happy to find out what the problem was and how to effectively control it in the future.