Phytoptosis.—This disease is known to occur only in Florida, where it is sometimes common enough to require remedial treatment. The affected portions of the foliage are more or less distorted and covered with an ashy white fuzz. The general vigor and fruitfulness of the plants are greatly reduced. The name applied to this trouble denotes its cause, an extremely small mite (Phytoptus calacladophora Nal.), which by its presence on the leaves or stems so irritates them as to result in the abundant development of modified plant hairs, which shelter the mites and form the fuzzy covering characteristic of the disease. A remedy for phytoptosis is available in the sulphur compounds. The following one is particularly recommended by Prof. P. H. Rolfs, to whom our knowledge of the disease is due:
Preparation of sulphur spray.—Place 30 pounds of flowers of sulphur in a wooden tub large enough to hold 25 gallons. Wet the sulphur with 3 gallons of water, stir it to form a paste. Then add 20 pounds of 98 per cent. caustic soda (28 pounds should be used if the caustic soda is 70 per cent.) and mix it with the sulphur paste. In a few minutes it becomes very hot, turns brown, and becomes a liquid. Stir thoroughly and add enough water to make 20 gallons. Pour off from the sediment and keep the liquid as a stock solution in a tight barrel or keg. Of this solution use 4 quarts to 50 gallons of water. Apply with a spray pump whenever the disease appears, and repeat if required by its later reappearance. The use of dry sulphur is also recommended.
DISEASES OF THE FRUIT
FIG. 43—POINT-ROT DISEASE OF THE TOMATO
(Redrawn from N. Y. Expr. Sta. No. 125)
Point-rot.—This trouble, called also "blossom-end rot," and "black-rot," occurs on the green fruit at various stages of development, as shown in Fig. 43. It begins at the blossom end as a sunken brown spot, which gradually enlarges until the fruit is rendered worthless. The decayed spot is often covered in its later stages by a dense black fungous growth (Alternaria fasciculata (C. & E.) J. & G. syn. Macrosporium tomato Cke.), formerly thought to be the cause of the rot, but now known to be merely a saprophyte. Point-rot sometimes occurs in greenhouses, but is more common in field culture. It is one of the most destructive diseases of the tomato, but its nature is not fully worked out, and a uniformly successful treatment is unknown. It has been thought to be due to bacterial invasion, but complete demonstrations of that fact have not yet been published. The physiological conditions of the plant appear to be important. The disease is worst in dry weather and light soils, where the moisture supply is insufficient, and irrigation is beneficial in such cases. Spraying does not control point-rot so far as present evidence goes.
Anthracnose—ripe-rot—(Colletotrichum phomoides (Sacc.) Chest.), is distinguished from the point-rot by the fact that it occurs mainly on ripe or nearly ripe fruits, producing a soft and rapid decay. Widespread losses from this cause are not common, but when a field becomes infected a considerable proportion of the crop within a limited area may be destroyed if humid or rainy weather prevails. Preventive measures only can be employed. These should consist in collecting and destroying diseased fruit and in staking and trimming the vines to admit light and air to dry out the foliage. Bordeaux mixture applied after the development of the disease would be of doubtful efficiency and would be objectionable on account of the sediment left on the ripe fruit.
DISEASES OF THE ROOT OR STEM
Damping off.—Young plants in seed-beds often perish suddenly from a rot of the stem at the surface of the ground. This occurs as a rule in dull, cloudy weather among plants kept at too high a temperature, crowded too closely in the beds or not sufficiently ventilated. Several kinds of fungi are capable of causing damping off, under such conditions.
Preventive measures are of the first importance. Since old soil is often full of fungous spores left by previous crops, it is the wisest plan to use sterilized soil for the seed-bed. When the young plants are growing, constant watchfulness is required to avoid conditions that will weaken the seedlings and favor the damping off fungi.