This is a photo of a tree on Jeff Burbrink’s property. Note a portion of the tree has turned color, months before it should. While this damage is not temperature related, it illustrates the long term effect root damage can have. This tree will be susceptible to temperature variations like we had last week, as well as droughts and other stresses. The initial stress may have happened years before.
The root system of this tree was damaged by construction 2 years before this picture was taken. The red line is the approximate location of a perimeter drain pipe that was extended from the house into the woods. A substantial portion of the root system was disrupted.
For years since, the tree has exhibited decline symptoms on one side of the tree due to root damage. It is not unusual for such trees to drop leaves in early summer on those first hot windy days. Most of the branches exhibiting color here have since died out. Photo provided by Jeff Burbrink.

By Jeff Burbrink
Ag & Natural Resources Extension Educator, Purdue Extension LaGrange County

LAGRANGE — People were buzzing last week when temperatures climbed into the 70s, which is unusual for February, a 28-degree departure from the daily average temperature. Within hours, the temperature dropped into the low 20s, which was a real shock to the system.

When we have unusual temperature fluctuations like that, people often ask how agriculture or backyard plants or insect populations will be affected. In general, my answer is there will not be much effect on things. A key consideration is that air temperatures can fluctuate wildly over a few days, while soil temperatures are much steadier.

Let’s consider the effects on insects, for example. When air temperatures are warmer than normal, the prevailing thought is that mild temperatures will mean more insects. Most insects overwinter in sheltered, protected areas. Some overwinter as adults, some as eggs, some as larva. They are built for this!

Consider yellowjacket queens, for example. As an adult, they bury themselves in the soil in November to overwinter. While our air temperatures fluctuated 50 degrees over 24 hours, the soil temperature barely registered a change. Its doubtful the yellowjackets overwintering in the soil even noticed what was going on.

Another insect/temperature related thought: insects can die horrible deaths that are weather warm related. For instance, many insects feed upon other insects. If warmer temperatures are favorable for the prey, it stands to reason the warm temperatures are also favorable for the predators, wiping out any potential boost to the population.

And there is disease. Insects are very vulnerable to molds, fungi, bacteria and other ailments that favor warm, wet environments. Given favorable weather conditions, entire populations of alfalfa weevil or gypsy moth have been known to die off due to fungal infections. Its one of the reasons that bug experts suggest one last look at an area to be sprayed when a weather front has moved through.

I am not concerned about the effect of the warm, then cold temperatures in our annual crops like corn or soybeans. The most likely plants affected are some of our perennial plants that do not die back to the ground, like trees or roses.

The concern for those perennials is small, but real. Plants that were under stress going into winter, are most vulnerable. Typically, the extent of the injury doe not show up until well into the first part of summer. Those first 90-degree days, especially when accompanied by drought, can expose limbs and branches that were damaged in February, long after people have forgotten the crazy February event.

Typically, the symptoms you notice are unexpected leaf drop from what looked like a healthy branch or limb, possibly with the death of the limb as well. The type of stress that encourage these symptoms are often root related, things like trees with substantial portions of their roots growing under driveways, or up against buildings, or recent digging or construction (within three years usually) that weakened the roots. Even trunk damage from string trimmers and lawnmower decks can affect a tree’s ability to cope with winter injury.