Control. - Destroy affected seedlings. Rotate crops, and do not follow with other susceptible crops. Keep down weeds on which disease occurs. Lime the soil at least eighteen months before planting to cabbage, using at the rate of two tons of quicklime to the acre. Black-rot (Bacillus campestre). - The bacteria causing this disease get into the sap tubes, turn them black, and cause the leaves to drop, thus preventing heading.
Control. - Practice crop rotation. Soak the seed for fifteen minutes in a solution of mercuric chloride, one tablet in a pint of water.
Carnation. Rust ( Uromyces caryophyllinus). - Produces brown, powdery pustules on stems and leaves.
Control. - Take cuttings only from healthy plants. Pick off diseased leaves. Spray once in two weeks with a solution of copper sulfate, 1 pound to 20 gallons. Keep water from leaves, and grow the plants at as low temperature as is compatible with best development. Stem-rot (Rhizoctonia and Fusarium). - The former produces a sudden wilting of the plant, and the stems are soon dead and dry. The latter produces a slow rot of the heart, one branch dying at a time. The treatment is the same.
Control. - In the field change the location every year. In the greenhouse sterilize the soil with steam. Cauliflower. See under Cabbage.
Celery. Early Leaf-blight (Cercospora apii). - A spotting and eventual blighting of the leaves early in the summer. Begins in the seed-bed. It is favored by hot weather, either wet or dry.
Control. - Spray with ammoniacal copper carbonate, 5-3-50, beginning in the seed bed and keeping the new growth covered throughout the season. Late Blight (Septoria petroselini var. apii). - A fungous disease, appearing late in the season, causing a blight of the foliage, and often destructive after the celery is stored.
Control. - As above, except that spraying should be continued up to harvesting time. In either case, the disease is practically controlled by growing the plants under half shade. Cherry. Brown-rot (Sclerotinia fructigena). - Attacks flowers, leaves, and fruit. The flowers die and decay, the leaves become discolored with irregular brown spots, and the fruit rots on the tree. Attacks also peaches, plums, and apples.
Control. - Spray with bordeaux mixture, 4-4-50, or lime-sulfur, 1-40, (a) just before the blossom buds open; (b) just after the blossoms fall; (c) make one or two more applications at intervals of ten days. Leaf-rust. See under Plum, p. 279.
Powdery Mildew (Podosphaera oxycanthae). - Attacks leaves and twigs, often causing defoliation. Serious on nursery stock. Spraying as for brown rot usually controls this trouble. If it appears, spray with lime sulfur, 1-40, or dust heavily with powdered sulfur. Leaf-spot (Cylindrosporium padi). - A fungous disease in which the leaves become thickly spotted with reddish or brown spots and fall prematurely. The spots often drop out, leaving shot holes.
Control. - Spray with lime sulfur, 1-40, or with bordeaux mixture, 4-4-50, as for brown rot. Winter Injury. - Trees so injured make a scant growth; many leaves turn yellow and fall about picking time; gum exudes at the crotches and about the trunk; sometimes the bark on the stock is entirely killed, in which case the tree languishes and finally dies.
Control. - It is thought that heavy applications of highly nitrogenous fertilizers in late summer favor winter injury. Do not stimulate the tree to too active wood development. Cut out the gum pockets and cankers, and paint them with a heavy lead paint. Chestnut. Bark Disease (Diaporthe parasitica). - A fungous disease, attacking the bark of the American chestnut. Limbs and trunk are girdled, and the tree dies. The disease is present in many of the nurseries.
Control. - Inspect nursery stock very carefully, especially about pruned stubs. Discard diseased trees. Make a careful examination of old trees, especially about old wounds and pruned stubs. If the disease is present, clean out the diseased wood with a gouge, and coat heavily with gas-tar. If the disease has progressed far, cut off diseased limbs or the whole tree and burn at once. Keep all wounds and pruned stubs covered with gas-tar. Chrysanthemum. Leaf-spot (Septoria chrysanthemi). - First appears as dark brown spots, which increase in size until the leaf dies.