APRIL
2012

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

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Check out these books by Tom Turpin:

Flies in the face of fashion

What's Buggin You Now?

 

 

 

04-12-12

Download the audio of On Six Legs: MP3, WMV.

Early Spring, Lawn Mowing
and Insects


This year I mowed the lawn for the first time on March 24th. Most of us who live in the northern and central areas of the U.S. aren't accustomed to mowing the lawn at such an early date. As a general rule, we haven't even put away the snow shovels, much less sharpened the mower blades by the end of March.

Now don't get me wrong; I have nothing against mowing grass. In fact, I rather enjoy the process. You know, the hum of the engine, the whir of the blades, the smell of the new-mown grass. The words of James Whitcomb Riley describe the feeling very well: "O, it's then the time a feller is a feelin' at his best, With the risin' sun to greet him from a night of peaceful rest."

But it wasn't as if I was overanxious to begin mowing grass. After all, by the time fall rolls around I get a bit tired of the grass-mowing thing; so starting the process early is never a good thing. The grass, though, was demanding to be cut - it was nearly 4 inches tall in some spots. So there I was, mowing the lawn a good three weeks early.

The grass wasn't the only thing off to a fast start this year. Many flowering plants - among them daffodils, tulips, forsythia, and dandelions and fruit trees - were also blooming early. For fruit production, that could be a bad thing. After all a frost and freeze could destroy the blossoms or developing fruit.

A warm winter and early spring always brings up the question of how such conditions will affect insects. Insects and plants are both cold-blooded organisms, so warm temperatures will accelerate development. That generally means that insect activity, like plant development, will be earlier than normal. But will such conditions lead to more problem insects?

The answer is yes, no and maybe. The reason is, that it all depends on the insect species and weather conditions going forward. In general, we are likely to observe more insect species in summers following mild winter and spring conditions. That is because some insect species do not survive cold winters but do survive milder conditions. These insects are likely to show up in higher numbers this year. In most years they are carried to our area by later-season winds.

june beetle grub
June beetle grub

There are insects that are adapted to survive winter conditions by hibernation or diapause, the slow-down of metabolism. Some of these insects have the added protection by being in a protected habitat, such as the soil. The grubs of the June beetles are in the soil and generally spend the winter "snug as a bug in a rug."

The survival of diapausing or hibernating insects is normally not affected by winter conditions. But early springs might be a different story because they could emerge before their food supply develops.

Ladybird beetle
Ladybird beetle

For example, ladybird beetles hibernate during cold periods. When temperatures warm up, such insects come out of hibernation and begin crawling around, looking for places to lay eggs. This means they may use up stored energy supply. When summer arrives, they might have died of starvation, or if they survived, end up depositing fewer eggs than normal. Consequently, the summer populations of the insect might be lower than when following a winter with colder temperatures.

The most important time period relative to population numbers of insects and a lot of other plants and animals is not winter. The most important time is when eggs are being deposited, and young are hatching. Cooler temperatures and rainfall during this time are a lot more important to insect survival than are cold temperatures during winter.

So as I was mowing my lawn in March, I know it is the type of year that would generate the question, "Does the warm winter and early spring mean we are going to have a lot more insects this summer?" I was correct, and my answer has been, "I don't know; we'll just have to wait and see what April and May bring." Just as April showers bring May flowers in a normal year, showers and a cold snap might bring fewer insects in this unusual year. 

 

Writer: Tom Turpin
Editor: Olivia Maddox