It might hardly feel like insect weather, but farmers are being reminded that even on the coldest winter days, there are steps they can take to make sure their crops do not get overtaken by pesky bugs.
John Gavloski is an Entomologist with Manitoba Agriculture. He says grain stored in bins at this time of year can still be susceptible to insect damage. That is because even on a day when it is -40 degrees outside, the temperature inside the bin in the middle of the grain can be well above the freezing point. And, that makes it warm enough for stored grain insects to survive.
Gavloski says at this time of year he tells farmers to check their grain every couple of weeks to see if there are stored grain beetles or other insects. If some of those bugs can be spotted, he suggests getting the aeration going on really cold days. One other trick is to move the grain out of the bin and onto a truck and then back into the bin again. This will help get the core grain temperatures cold enough to kill the beetles.
"Again, it can be -50 outside but in the middle of that grain it's still warm enough for things to survive," says Gavloski.
In case you are wondering if our cold weather this winter has been enough to kill off the insects that ravage our Manitoba crops in summer, Gavloski says some will definitely die off, while others are hardy enough to survive. He notes a lot of insects are well adapted for our prairie winter climate.
Those that will not make it, are a lot of the aphid species. Gavloski says aphids that infect our cereal crops in Manitoba, like the English Grain Aphid and the Bird Cherry-oat Aphid are killed off annually and need to re-invade each year. The same is true for Soybean Aphids.
Other insects that cannot survive our winters are Armyworms and the Diamondback Moth. Gavloski says Armyworms posed a big problem in our cereal crops and forage grass last year, while Diamondback Moths damage not only canola but also cruciferous plants in our garden like broccoli, cauliflower and cabbage.
Gavloski explains that insects which have to re-establish themselves come from areas that do not get cold winters. This could be from the southern States, Mexico or further south. Gavloski says some insects will actually migrate, such as the Monarch butterfly, Painted Lady butterfly and Armyworm. However, a lot of insects do not migrate but get caught up in the winds.
"It's not like they are getting blown up from Texas to Manitoba on one wind," says Gavloski. "Often it's they are getting moved part way here and then another batch gets blown further north."
He notes sometimes you can see the progression where aphids start showing up in some of the U.S. Midwest states and then the northern states and then finally in southern Manitoba.
But, Gavloski says there are definitely insects that survive our winters well, including grasshoppers. He notes the soil temperature needs to get down to about -15 degrees Celsius, five centimetres down, to kill grasshopper eggs. However, even when the air temperature is -30 degrees, Gavloski says there is normally enough snow to act as insulation, preventing the soil temperature from getting cold enough to kill the grasshopper eggs.
Gavloski says Flea beetles are also able to survive our winters by finding places underneath leaf litter that eventually get covered in snow and provide a proper nest. Cutworms are also hardy enough to survive.
According to Gavloski, there are at least a couple of reasons why some insects survive, while others do not. As mentioned, one factor is where they choose to nest over winter, but there is also the bug's supercooling point to consider.
"Each insect has what we call a supercooling point," he explains. "And that means once you hit that temperature, they are dead. And that point differs greatly for different insects."
As mentioned, the supercooling point for grasshopper eggs is -15 degrees, but Gavloski says many other insects will die as soon as the temperature dips below the freezing point.
Meanwhile, when it comes to mosquitoes, Gavloski says unfortunately even bitterly cold temperatures are not enough to wipe out populations. He notes what is tricky about mosquitoes is there are quite a few different species and some are hardier than others. He notes that because their supercooling points are somewhat different, even a few weeks of -40 degrees would not kill off the populations.