Читать книгу Cornell Nature-Study Leaflets - New York State College of Agriculture - Страница 23

The object of this year's work is the economic side of insect-study. Many pupils do not continue these studies to high school or college. Yet if they have homes with gardens or trees in city or country, they must learn to cope with the many insect enemies that feed upon cultivated plants. They should also learn to discriminate between insect friends and foes. They should learn the best methods of combating the foes and preserving the friends.

Explain first that in fighting an insect enemy we must know how it eats. If it inserts its beak in the stem of the plant there is no use trying to kill it by putting poison on the leaves.