Cold Killing Insects

Russell Groves, Associate ProfessorColorado_potato_beetle_leptinotarsa_decemlineata_insect
Department of Entomology
College of Agricultural and Life Sciences
(608) 262-3229


These arctic temperatures may be good for something. Russell Groves tells us the impact on insects.


Total Time 3:04
0:19- Benefits of subzero temperatures
0:41- How temps kill insects
1:00- What we need to kill the bugs this way
1:29- Effects outside of Wisconsin
1:50- Types of insects effected
2:54- Close Out

Russell Groves cold killing insects

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Sevie Kenyon: You tell us that this sub zero weather is actually good for something. Can you describe what that is?

Russell Groves: Yeah, as we’re speaking, the forecast tonight may be about twelve below zero. What that is going to do for us is it’s going to provide enough chilling degree-days, or cold temperatures, that’s going to kill a lot of insects that are trying to [survive] over winter. This is the year we need; to set them back. 

Sevie Kenyon: Explain to us how it works?

Russell Groves: The air temperature itself can have the ability to directly freeze an insect, but it is a little bit challenging for you know insects that are in the soil, to be exposed to that air temperature. And in fact, a little bit of the snow that we have is a real good insulator. So what we do need is extended periods of cold temperature, and we also need a little bit of this wind. So where we have these cold temperatures and we have these extreme wind chills, when the wind comes and it blows the fields wide open, it really allows that cold temperature to reach the soil and our frost line to go deep, and by doing that can get to these insects, and drive the temperature down to levels that can be killing.

Sevie Kenyon: This isn’t just about killing bugs in Wisconsin.

Russell Groves: this is sort of a big, synoptic, weather event that’s really over much of the upper Midwest and even over the east. So this effect is going to be felt across many many areas of the state, Emerald Ashborer, and Emerald Ashborer populations might be getting effected by this, especially in the areas where we’re really getting these cold temperatures. And the same phenomenon is the case, we have to have these extended periods of cold temperature in order for the interior of the trees to reach the temperatures that can be a killing temperature. In the case for a lot of our insects that effect crops, again where they’re in the soil, we have to have these extended periods, and it is, it’s happening over a very large area in the country.

Sevie Kenyon: What other insects are affected by such cold temperatures?

Russell Groves: As a vegetable entomologist here in Wisconsin, probably a couple of the insects that I deal with, most often, one would be the Colorado Potato Beetle. And of course that’s probably our key pest with potatoes. That’s an insect that over winters in the ground, usually winters on average over twelve, to fifteen, maybe twenty inches in the soil, and so it’s these types of temperatures that are reaching these kinds of populations. Another one is Striped Cucumber Beetle. In our squashes are Cucurbits, and insects that over winters not in the ground, but on the soil surface, again when these fields blow open because of this wind and this cool, it’s getting to them. And we’re getting a few of them.

Sevie Kenyon: We’ve been visiting with Russell Groves, Department of Entomology, University of Wisconsin Extension and the College of Agricultural and Life Sciences, now celebrating 125 years, and I am Sevie Kenyon.



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