
                         Roanoke Times
                 Copyright (c) 1995, Landmark Communications, Inc.

DATE: THURSDAY, March 31, 1994                   TAG: 9403310291
SECTION: CURRENT                    PAGE: NRV8   EDITION: NEW RIVER VALLEY 
SOURCE: Joe Hunnings
DATELINE:                                 LENGTH: Medium

WINTER DIDN'T BUG BUGS

Every eight to ten years we get a real winter here in Virginia, and the temperature drops to some new record low. Water pipes freeze and split, cars don't start, the cat won't set foot outside, and things are just generally miserable for all living things for a few days.

After it all passes there are always a few folks (usually deperate reporters looking for a story) who want to find some benefit in all of it. For instance, it seems logical to think that all the sub-zero weather must have done something bad to all those nasty insects out there, right?

Wrong! While a little cold weather might make us warm-blooded animals who have been walking upright in the woods for only about 1.5 million years a little chilly. But, those six-legged critters crawling along in the woods - insects - have been around for - well, beetles maybe for about 190 million, and grasshoppers, crickets, and cockroaches for about 350 million years.

Face it, these guys are playin' for keeps, they've seen it all - from ice ages to tropical times. A few days and nights below freezing is not going to faze them much at all.

While you might think soil-inhabiting insects would suffer most in cold weather, they probably suffer the least. Consider the immature stages of turf pests, such as white grubs (Japanese beetles, masked chafers, June beetles, etc.). These insects spend the winter three to four inches below the soil's surface; they tunnel to this depth in response to declining soil temperatures in the fall.

What probably happens is that the soil near the surface begins to cool, and these grubs migrate to soil that has higher temperatures - which is a few inches deeper. When winter air temperatures drop below zero Fahrenheit (Blacksburg went to -15 F. in 1985, and to about -19 F. this year), soil temperatures are much warmer.

In general, soil temperatures at two to three inches below the surface remain at the freezing point (32 F.). With a snow cover of a few inches, the soil at the surface will remain close to the freezing point. Otherwise, it will drop a little below that.

When you go deeper in the soil, the temperature increases! So, where soil insects spend the winter, the temperature very rarely drops below the freezing point of water - and that is not a threat to their survival!

Now, some insects can be killed by low temperatures - flies for example. The house fly overwinters as adults, larvae, and pupae in protected locations. This species is very susceptible to cold temperatures, and is easily killed below 32 F. But, I don't think we will see much of a difference in the house fly population this spring. Indeed, I have every confidence that this very successful insect will bounce back with sufficient numbers to annoy us all summer.

Cold weather has rarely if ever had any serious impact on the insect pests that have adapted to the human environment, especially soil insects. So, what does that leave us? Fire and flood, I guess!

Joe Hunnings is the Virginia Cooperative Extension Service agent for agriculture in Christiansburg. If you have questions, call the Montgomery County extension office at 382-5780.

by CNB