Insects Help or Nuisance
When insects are mentioned what comes to your mind? Do you think of insects that spread disease, feed on man’s crops and eat holes in his clothing?
Or do you think about the benefits insects bring? Do you think of the services they perform and the products they yield-shellac, silk and honey, to mention a few?
To some it may seem that all insects are pests and that the world would be better without them. But did you know that, of the more than 800,000 kinds of insects known to man, the vast majority are acknowledged to be beneficial? In fact, many of them do things that are vital to man’s existence.
Pollinating and Building Soil
One such vital service has to do with the relationship of insects to plants. Over 85% of flowering plants rely on insect pollination. It isn”t just bees that pollinate; flies, beetles, moths, butterflies and others aid in this vital work. How long would it take for many of these plants to die out without the efforts of these insects? We’d be in a mess if that happened!
As scavengers, some insects have a role in the creating of food for plants. They eat dead matter and their digestive systems break it down into different chemical combinations.
Even when they die they add fertilizer to the soil through decomposition. Insects aerate soil by digging down and making tunnels through which water filters down.
What About Plant-Eaters?
Amazingly, research shows that insects prefer plants that are in some way deficient, perhaps through poor soil, the plant’s age or some unfavorable growing condition that was responsible for the deficiency.
In one study Dr. William Albrecht of the University of Missouri conducted a series of tests with spinach. He found that insects known as thrips destroyed the spinach grown on poor soil. But the spinach grown on good soil survived.
An observation was made about two crops of lettuce. One crop had been stunted by unfavorable growing conditions and was attacked by aphids. But no aphids were found on lettuce cultivated under favorable growing conditions in the same soil.
Commenting on why insects prefer plants that we would consider inferior, the book Our Poisoned Earth and Sky states:
“The nutritional needs of insects are very different from those of man and animals. Where man thrives best on a high protein diet, insects go for carbohydrate. They need it more in their system of operation. An insect can jump the equivalent of the Empire State Building in one jump, comparatively speaking, and it needs a lot of carbohydrate for that energy. So when one plant has more carbohydrate than another, an insect will seek it out and prefer it.”
So when insects eat garden plants, might they not be telling us something? Are the plants receiving needed nourishment from the soil? Can something be done to remedy an unhealthy condition in the plants?
Plant Control
Many insects show a preference for a particular kind of plant. Their feeding habits prevent various plants from running riot.
A case in point is the prickly-pear cactus. This plant was unwisely introduced into Australia. There being no insect enemies to keep it in check, the prickly-pear cactus spread rapidly. Within a short time it made millions of acres of land practically unfit for agriculture.
Then, in 1925, 2,750 cactus-moth eggs were sent to Australia from Argentina. Eventually millions of moth eggs were distributed in areas where the prickly-pear cactus had gained a foothold. The hatched caterpillars of the cactus moth did their job well. They burrowed into the joints of the prickly-pear cactus and thus destroyed it. At last this cactus ceased to be a scourge for Australia.
Another example of plant control by insects involves St.-John’s-wort or the Klamath weed. This yellow-flowering weed was brought to the United States from Europe. It was noted in the United States in 1793, having been introduced to Pennsylvania first of all. By 1940 thousands of acres of rangeland in northern California were ruined by this weed. Chrysolina, a group of Eurasian beetle species, were released in the western United States in the mid-1940s. Hundreds of thousands of acres of land were freed up.
But have these insects become a pest since the time the Klamath weed was brought under control? No. Scientific American commented:
“Because stands of Klamath weed are no longer extensive and the infested areas are now widely separated, all of the immigrant insects, totally dependent on the weed for survival, have decreased in numbers. Fortunately their ability to locate new infestations and their high rate of reproduction have prevented any important resurgence of the weed. All indications are that this noxious range plant will be held in check and that its insect controls will perpetuate themselves.”
There is no way of knowing just how many plants could become pests if it were not for insect control. But the foregoing examples well illustrate that man needs the help of insects. Rather than being a nuisance in the vast majority of cases insects are a great help.
Having said all of the above, it seems there is general agreement among scientists that the ecological balance wouldn’t be greatly upset if mosquitoes were eradicated, as they don’t seem to serve any real useful purpose. It would also save millions of lives each year as mosquitoes spread a number of diseases, perhaps the best known being malaria.
