Dr. Clark says:
But not only does every tree have its own enemies, but every part of the tree has its foes. The bark has its borers and its scale, the leaf its lice and curlers, the blossom its moths, the fruit its borers. Each enemy knows exactly the weakest part of the citadel he has to attack. He knows the exact moment when his attack will be most effective. He has the accumulated experience of a thousand ancestors behind him. H e never makes a mistake in his maneuvers, or fails to avail himself of the psychological moment.
What, then, can I, a mere man, do with a thousand watchful, unwearied foes to combat—a mere man, with only one pair of hands and one poor brain to oppose these multifarious enemies; or, if I do not forget to count my Portuguese assistant farmer, two pairs of hands and two poor brains at the most and best? Shall I give up the fight and call myself beaten by the worm, and the moth, and the crow, and the weed—which I have hitherto forgotten to mention, but which is always ready to spring up and take my plants by the throat and strangle them?''