CHAPTER IX.
PHYTOPATHOLOGY. DERIVATION AND MEANING.
History. References in the Bible—Greeks and Romans—Shakespeare—Rouen law—Superstitions—Malpighi and Grew—Hales—Unger—Berkeley—De Bary, etc. Physiology and Biology—Diagnosis—Etiology—Therapeutics. Study of causes.
Phytopathology, from Greek words which signify to treat of diseases of plants, comprises what is known of the symptoms, course, and causes of the diseases which threaten the lives of plants, or bring about injuries and abnormalities of structure. As a distinct and systematised branch of botany it is a modern study, the history of which only dates from about 1850, though the subject had been treated more or less disjointedly by several authors during the preceding century, and isolated records of diseased crops, fruit-trees, etc., exist far back in the history of Europe. The existence of mildews and blights on cereals indeed was observed and recorded by the writers of the older books of the Bible, half a dozen references to such blights being found in the Old Testament, as well as others to blasted fig trees, etc., in the New Testament. Aristotle, about 350 B.C., noticed the epidemic nature of wheat-rust. The Greeks and Romans were so well acquainted with such diseases that their philosophers speculated very shrewdly as to causes, while the people dedicated such pests to special gods. As regards the Middle Ages, we know little beyond the fact that blights and mildews existed, but Shakespeare's reference in King Lear (Act III., Sc. 4) leaves no doubt as to his acquaintance with mildew in the 17th century, and other authorities bear out the same. Even the law took cognisance of the danger of wheat-rust in 1660 in Rouen (Loverdo). Prior to the 18th century, however, only meagre notes on the subject occur scattered here and there among other matters, and much superstition existed then and later regarding these as other diseases.
Malpighi, in 1679, gave excellent figures of leaves rolled by insects and of numerous galls, the true nature of which he practically discovered by observing the insect piercing the tissues; previous observers—Pliny knew that flies emerge from galls, but thought the latter grew spontaneously—having nothing but superstitions and conjectures to offer. Grew, in 1682, also gave a capital figure and description of a leaf mined by "a small flat insect . . . which neither ranging in breadth nor striking deep into the leaf, eats so much only as lies just before it, and so runs scudding along betwixt the skin and the pulp of the leaf, leaving a whitish streak behind it, where the skin is now loose, as the measure of its voyage"—a by no means inadequate description of the injury and its cause.
During the eighteenth century several academic treatises or dissertations dealing with diseases of plants appeared.
But as a rule we only find disjointed notes. Hales (1727-33) discusses the rotting of wounds, canker, and a few other matters, but much had to be done with the microscope ere any substantial progress could be made.