It can seem like an efficient way to solve two problems at once — add an insecticide in with the fungicide on canola and, voila, all your pest troubles go away. But not so fast. While applying an insecticide when pest insect levels are at or above threshold may be the right move, adding an insecticide as “cheap insurance” can actually end up being a very costly mistake.
As John Gavloski, entomologist with MAFRI, explains, there are two major pitfalls to this spray-it-because-you’re-going-in-anyway mentality. The first is the very real risk to pollinators. Canola doesn’t rely on pollinators to set seed, however, pollinators working in the crop will always bump yield, sometimes very significantly (for just how much, you’ll have to watch the video below).
The second very real risk is that most of the registered insecticides for use on canola are very non-selective, which means an application will wipe out predatory insects as well. These predators of insects such as bertha armyworm can actually do an amazing job of keeping populations in check and can and do eliminate the need for an insecticide application in many years.
So while there are sometimes reasons to spray, a “just in case” application of insecticide can actually cost more in the long run, Gavloski says.
In this video, filmed at the Manitoba Agronomists Conference held at Winnipeg, Man., last month, John talks pollinator yield bump and explains why you may want to hold off booking a spray, just because your neighbour has the planes flying to control bertha armyworm.
If you cannot see the embedded video, click here.