7.1 What is the Pest and What is the Problem?

Man thinks that pests (insects and diseases which attack crops) are absolutely harmful. But is this idea really true? From the perspective of man’s benefit, it seems to be right. However, from an ecological point of view, it is completely wrong. Everything in an ecosystem interacts and all elements are necessary to keep ecological balance on the natural environment.

So-called harmful insects are, in ecological terms, consumers of the first order. As we learned in Section 1.1, the role of the insects in the food chain, is not harmful but rather important and in dispensable. If there are no insects, consumers of the second order cannot survive, and the food chain will be disturbed.

In a well-balanced ecosystem, the numbers of the insects are kept within certain limits which are not harmful to plants. But when disturbances come form outside, the insects may break out suddenly. And become harmful to plants (crops). If we observe this fact carefully we can realize that the problem is not the insects, but the cause of the imbalance in the ecosystem which allows the insects to increase. The insects should be seen as teachers who tell us that we have done something wrong to the ecosystem. Therefore, before deciding that the insects are bad and should be removed, we must discover why the insects have broken out.

The same thing can be said about plant diseases. Plant diseases occur as a result of the outbreak of specific micro-organisms or so-called disease germs (e.g. some kinds of nematode, fungi, virus, etc.). These disease germs are usually limited in numbers, so they are not harmful to plants. But when the soil ecosystem is disturbed and conditions are created in which disease germs can easily break out, then plant diseases occur. The problem is not the existence of the disease germs in the soil but the disturbing factors which create the imbalanced soil ecosystem. Therefore, it is very important for disease prevention to remove the disturbing factors (e.g. continuous cropping, use of agricultural chemicals, etc.) and create a balanced soil ecosystem.