cherry tree. The limbs affected are practically worthless, and by destroying them the disease is kept from spreading farther in the branch and the forming spores are destroyed before they have an opportunity of getting a foothold elsewhere.
If the horticulturist understands the methods of growth and propagation of a destructive fungus, he is better able to take the step that may lead to the eradication of the pest. Let another example be taken, namely, the apple- leaf rust, which in some parts of the country is a serious menace to the orchardist. It is recognized as yellow blotches upon the foliage, followed by groups of deep cups in the under half of the leaf tissue, where orange-colored spores are produced in great abundance. The life cycle of this fungus, Gymnosporan- gium macropus, Involves two hosts; that is, it lives in one stage upon the common red cedar and in the next it infests the apple tree. Upon the cedar the fungus, forms galls of a chocolate color half an inch or more in diameter, which during the spring rains become swollen and have a gelatinous exterior. In this jelly the spores are produced that find their way to the apple tree and there form, after vegetating for a few days, the destructive rust. It is seen that in a case like this the most important thing is to destroy the cedar-galls, for in them the fungus passes the winter; and this can be done by picking and burning. To those who do not set a high value upon their cedar trees, the end may be accomplished by removing the cedar trees that stand at all near the infested orchard.
But there are many destructive fungi that pass their whole life upon the same plant, and the method mentioned for the apple rust would not obtain. In many such cases the use of fungicides has proved effective. The apple-scab (Fig. 721), due to a fungus (Fusicla- dium dendriticum),is a good case in point. It infests both the leaf and the fruit, causing irregular blotches upon
The branch is dead from the effects of the fungus.
both, and frequently destroying the crop. Many experiments have demonstrated that this scab-producing fungus can be kept down by the use of the Bordeaux mixture and various other similar substances. The fun
gus thrives below the skin of the fruit and the epidermis of the leaf, producing spores in abundance upon the surface. The fungicide, when left in a thin film upon the susceptible surface, prevents the germination of the spores and the extrance of the fungus. It likewise may kill the spores in the places where they are formed and before they have been transplanted to another part of the plant. The fungicide cannot act as a cure in the sense of replacing the diseased,by healthy tissue, but may, by destroying the spores,so prevent the spread that the healthy parts may predominate. In the case of foliage, the spraying is chiefly preventive, and should be particularly directed to the younger leaves, the older ones, with the fungus already established in them, in time falling away. With the ordinary fruits there is no
such succession, and the aim is to have each apple or pear coated with the fungicide.
As a rule a fungus that attacks the fruit also infests the leaves, and may likewise thrive in the stems. From this it is gathered that the spray should be very thoroughly applied to all parts of the plant, in order that the foliage may be kept in vigor and make the required food substances for the growth of the fruit, and the latter saved from decay due to direct attack of the fungous germs. But this is not enough. From what has been remarked concerning the hibernation of fungi, it goes without long argument that much can be done by thorough sanitation in the orchard and fruit garden when the crop is off and the plants are at rest. In short, the foliage of a blighted orchard or vineyard is too important to be overlooked in considering the subject of fungous diseases. The pear leaves, for example, may be infested with the leaf-spot, Entomosporium maculatum, and spraying may have kept them from falling prematurely and a good crop saved thereby, but the old leaves, as they drop in autumn, are more or less infested with the disease, and, as far as possible, should be destroyed before the winds have scattered them. In the same way the black-rot of the grape (lastadia Bidwellii) maybe carried over in the foliage and the mummy berries that are left upon the vines. Here, again, the spray pumps can.be largely supplemented by picking, pruning and burning. In the winter care of vineyards we can take a lesson from the grape growers of Europe, where much care is taken to clean up after every crop. They do not stop with the gathering of the refuse, but spray the leafless vines in winter, and the trellises as well, with Bordeaux or plain solution of cupric sulfate. The subject of remedies for fungous diseases would be slighted were not emphatic words used in this connection. It is folly to delay the