The introduction of the turnip as a field crop is one of the most important events in the history of British agricul ture. It has rendered possible a rota tion of crops which has been extremely advantageous, and has made the supply of butcher meat more constant, by pro viding a supply of winter food for cattle and sheep, whereas formerly all de pended on the pasture. As a field crop turnips were not raised in Great Britain till the end of the 17th century. Turnip husbandry was introduced into Rox burghshire from Leicestershire about the year 1764, but was soon carried to a perfection in Scotland far beyond what it had previously reached. The climate of Scotland is well adapted for it, as is also that of Ireland. Turnip crops in Great Britain suffer very much from the two distinct diseases called anbury, or club root, and finger-and-toe. Superior culture is the best means of preventing these diseases. Plants weakened by drought are liable also to suffer from a white mould, a species of Oidium, which attacks the leaves and greatly injures the plant.
The turnip crop has to encounter many insect enemies. The most destruc tive in recent years have been the turnip fly (Phyllotreta ncmorum, Chevrolat), which devours the young plants before they are strong enough to be thinned.
The leaves of the young turnip plants are also attacked and often much injured by the green fly or turnip aphis, Aphis rapx (Curtis) ; by the maggots of two kinds of Diptera—Phytomyza nigricor nis (Maquard), the black-leaf miner, and Drosophila planes (Fallen), the yel low-leaf miner; by the caterpillar of the diamond-back turnip moth, Cerostoma xylostella (Curtis) : by the caterpillar of the common dart moth, Agrotis segetum (Westwood) ; by the grubs of the turnip sawfly. Athalia spinarum (Fabricius) ; and by at least two varieties of weevil, Cumuli°, the most destructive being the little Curculio, Centorhynchus contractus, 1-14 inch long, which punctures the seed leaves with its rostrum. The diamond back moth fortunately seems to pay its visits of destruction at long intervals. It played great havoc with the crop in England and Scotland in 1891, destroy ing it beyond recovery in many parts. In Ireland the attack was lighter. Ear lier serious attacks occurred in 1851, 1837, and 1826. For all insect attacks the best preventive measure is a dressing of stimulating manure to force on the growth of the plants. Spraying the crop with a mixture hurtful to the insects, by means of the Strawsoniser, an air power distributor, is also recommended.