Good can come out of our deep freeze of last week. Insects are major pests in the garden. Let’s look at what may have been happening to the insects while our region sustained the coldest stretch of freezing temperatures in many years.
Insects are curious creatures. There are more species of insects than any living organism, and unlike many other organisms, they are ectotherms. Ectothermic organisms, “coldblooded” organisms, do not generate heat. (Recall other common ectotherms are fish, amphibians, and reptiles.) Unlike humans, which have a usual body temperature of 98.6° F, the internal temperature of an insect is that of their surrounding environment. They are definitely affected by temperature.
Therein lies the good news of our recent Arctic Blast.
Many animals hibernate when winter temperatures become adverse. The response of an insect to adverse conditions is to go dormant. Just like plants that go into dormancy, insects will go into an inactive state where metabolic activity is slowed or halted, which in turn slows and ceases.
Insects instinctively prepare for winter by spontaneously going into state of rest called a diapause. This state of rest is controlled by hormones and occurs prior to the onset of adverse conditions of winter months. The hormones trigger changes in the insect’s physiology, allowing the organism to go into a rest period. This process is uniquely expressed by the genetics of a particular insect. The onset of diapause is a gradual response to environmental triggers such as temperature and the shortening daylengths as winter months approach.
An insect’s diapause ends mid-winter, but they remain in a dormant state until environmental conditions become favorable. Insects are sluggish at temperatures below 50° F but will experience freeze when temperatures drop below minus 4° F. Furthermore, while some insects survive brief temperatures in the 20s, fewer survive when temperatures drop to the teens (crops.extension.iastate.edu).
This is the good news for our region—as temperatures dipped to single digits for many hours, insect populations may have succumbed. Even better news is that temperatures below freezing for at least five days may be lethal to some insect populations.
This still does not mean that we can expect an insect-less season ahead. However, hopefully we’ll see fewer insect populations this growing season.
Stay warm and enjoy our big thaw after our February big freeze.
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