Powdery mildew

“ How comes it to pass that the mildew, blight, call it what you will, should be so partially distributed that of two adjoining fields, nay that of two adjoining ridges in the same field, one may be entirely exempt from the disease, and the other severely suffer by it? But every farmer knows that this is no imaginary or even uncommon case: the track of the mildew is oftentimes remarkably distinct, which it would hardly be if the air were impregnated with this poisonous and prolific dust. ”

“ To treat plants affected by mildew, add one gill of the liquid, prepared as above, to six gallons of water, and mix well together. This is to be freely syringed upon the plants every other day. It will not only arrest mildew, but prevent it. Sudden changes of temperature, as cool nights following warm days, tend to the production of mildew, and with house plants, these sudden changes should be carefully guarded against. ”

“ In this way the disease is spread rapidly, continually eating into the timber, which is first rendered brittle, and then reduced to powder. A strong growth of the fungus gives the appearance of mildew on the wood, and produces an unpleasant musty smell. The spores of the fungus will find a way through brickwork, concrete and similar material, in order to reach woodwork that may be on the other side. Dampness and a close atmosphere are essential to the growth of dry rot, and it is under these conditions that it spreads most quickly, the fungus soon dying when exposed to the fresh air. ”

“ From the seed which is sown, these spores, for which the substratum was most suitable, will more easily germinate, and their development will follow the more quickly. The favoured germs will suppress the less favoured, and grow up at their expense. The same relation exists between them as between the seeds, germs, and seedlings of a sown summer plant, and the seeds which have been undesignedly sown with it, only in a still more striking manner, in consequence of the relatively quick development of the mildew fungus. ”

“ As we have mentioned, they are curious because they dwell outside the plants they attack. Rose mildew is unfortunately all too common in every garden, it may be recognised as a white powder covering leaves and buds. Under the microscope, in the summer we shall find that it consists of a number of thread-like structures, not unlike those of the common white mould and that there are a number of erect chains of spores. Towards autumn, a further examination will show us many round dark-brown structures from which project a number of minute threads. ”

“ The spores germinate on rose leaves and start the disease anew.
There will be no difficulty in finding mildews; they are all very similar to the rose mildew in general but they all differ in detail. The gooseberry [188] mildew for example, has a large number of threads running from its winter spheres and each thread is terminated by a little group of branches. The sacs which fall from the opened sphere in the spring, only contain four spores in this case.
The animal enemies of the farmer, so far as they concern the microscopist are more difficult to study. ”

“ Among plants, most of these degenerate creatures belong to the group of Fungi. The rust and smut on wheat, the mildew on fruit, and nearly all the thousand spots, blemishes, and diseases of cultivated and other plants, are the result of the parasitism of some members of the family of fungi. ”

“ The corn-mildew, the hop-mildew and the vine-mildew are, for example, parasitic upon living plants, and the mildews of damp linen and of paper are saprophytes (Gr. σαπρός, rotten) , that is, they subsist on matter which is already dead. As regards mildews in general, the conditions of life and growth are mainly suitable nutrition and dampness accompanied by a high temperature. The life history of the same species of mildew frequently covers two or more generations, and these are often passed on hosts of different kinds. ”

“ The brown rot of grapes is a diseased condition of the fruit caused by the presence of a minute parasitic plant—a fungus—that develops by absorbing the tissues of its host. It attacks not only the fruit but also the leaves and young shoots, on which it often appears as a whitish, mildew-like covering, which has given the disease its other common name of downy mildew. This fungus reproduces by means of minute particles called spores, corresponding in function to the seeds of higher plants. ”

“ We therefore look upon this as an invaluable remedy in these states of mildew, whether occurring on the vine, the hop, the turnip, the cucumber, or on other plants, as we have frequently seen it in hothouses—a circumstance which shows the near affinity of all those forms of epiphytes, which, perhaps, after all, only vary with the variations in the structure and economy of the different plants on which they occur.
13. Oïdium abortifaciens (Ergot) ; Secale cornutum (Ergot of Rye) .—The black horn-looking spur which occurs in rye and other grasses was formerly looked upon as a distinct fungus ”

“ Flock does not affect all the mushrooms in a bed at any time, and I do not believe it spreads in the bed, or, to use the expression, becomes contagious. If one spot of mildew appears upon a cucumber, rose, or grape vine indoors, and is not checked, it soon becomes general all over the plant or plants, and if one spot of mold occurs in a propagating bed and is not checked at once it soon spreads over a large space and destroys every cutting or seedling within its reach, but this is not the case with flock in a mushroom bed. ”

“ Common wheat is more subject to this destructive disease than that which is bearded, especially if the land be newly dunged. As, however, it is highly probable, that the greater dampness of some soils, together with their being over-shadowed by too thick foliage, affords one permanent cause of mildew, Dr. Darwin recommends the land to be properly drained ”

“ Where this disease has already infested the plants, a brisk shower of rain, succeeded by a smart wind, is believed to be the most efficacious remedy, to prevent its farther progress. If the mildew be observed before the sun rises to its meridian power, it will be advisable to send two men into the field, furnished with a long cord, of which each should hold one end: by dexterously drawing this rope over the ears of corn, the dew will be removed, before the heat of the sun dries and reduces it to that viscous state, in which it obstructs the perspiration of plants. ”

“ The filaments are attached to the surface of the leaf by suckers, which are not so readily seen in this species as in some others. A mildew growing abundantly in autumn on the garden chrysanthemum, however, shows them very satisfactorily if a bit of the epidermis of a leaf on which the fungus is just beginning to grow is sliced off with a sharp razor and mounted in dilute glycerine, or water, removing the air with alcohol. ”

“ In Onygenei, the receptacle is either club-shaped or somewhat globose, and the [Pg 76] peridium is filled with branched threads, which produce asci of a very evanescent character, leaving the pulverulent sporidia to fill the central cavity. The species are all small, and singular for their habit of affecting animal substances, otherwise they are of little importance. The Perisporiacei, on the other hand, are very destructive of vegetation, being produced, in the majority of cases, on the green parts of growing plants. To this order the hop mildew, rose mildew, and pea mildew belong. ”

“ Into this area dead leaves are blown, and worms and slugs and snails inevitably find their way, and are washed by the rain into the stagnant gully, which becomes a place for putrefaction and the cultivation of mildew, the spores of which are necessarily blown into the house to infect the food which is stored there. Not only is the area closed by a fixed grating above, but the window is securely and permanently barred, so that this dry area (?) , with its mildew trap, cannot possibly be cleaned without pulling the house to pieces. ”

“ Many greenhouse insects can be kept more or less in check by careful and effective hosing of the plants at proper times. At this season roses, grape vines and other plants are often affected by mildew; an effectual remedy is to paint the hot-water pipes with a mixture of sulphur and lime, put on as thick as ordinary whitewash, once each week until it is checked ”

“ In sections where mildew is practically sure to come, sulphur should be used regularly as a preventive without waiting for the appearance of the disease. There are, however, many locations, especially in the interior valley, where the occurrence of mildew is rare in sufficient volume to do appreciable harm, and then sulphuring should depend upon the weather, which favors mildew or otherwise. But be always on the watch and have everything ready to sulphur immediately; also learn to recognize the conditions under which appearances of mildew become a menace. ”

“ There are about sixty different kinds of mildew, a special variety for nearly every special kind of fruit or vegetable; and, if a decaying berry of the rarest sort is exposed to the open air, it will soon be covered with its specific kind of mold. ”

“ Whatever preserves corn in a healthy state, whether wheat, barley, oats, peas, or any thing else, arms it against the attack of those parasitic fungi which, when they have taken possession of the plant, we call the mildew, and which is rather to be considered as the consequence of previous unhealthiness than as a disease per se. Too great luxuriance and too little are alike injurious; a man may kill himself by eating too much as well as too little, and die of fat, instead of famine. The adaption of seed to soil and climate, by promoting the health may repel the mildew of the corn ”

“ Phloxes grown in rather shady places will, in damp weather, fall victims to mildew on the leaves. Spraying with Bordeaux mixture the end of June and middle of July should prevent this. Roses also have a tendency in warm, damp weather to mildew, which can be prevented by spraying the plants with Bordeaux mixture.
Kerosene emulsion may also be prepared, and is excellent for killing, both the small green aphids that often cover the leaves of Roses, and other hard, scaly insects. Following is the receipe:
Put one cake of laundry soap shaved fine into one gallon of water. ”

“ I am sorry to say that seedlings of these foreign varieties have the same tendency to mildew shown by their parents. The Late Emerald was originated in the old garden at Newburgh, and is a sad example of this fact. For many years it thrived in its birthplace without a trace of mildew, but on my own place it has behaved so badly that I do not recommend it. ”

“ TOMATO-LEAF RUST.—The leaves of the plant attacked by this disease rapidly become covered with a dull brownish velvety mould, or fungus, known as Cladosporium fulvum. From the mouldy spots and patches thousands of spores are readily carried by a slight current of air to the surrounding healthy crop, and unless prompt measures are taken to check the pest the whole house is rapidly involved. Excessive atmospheric moisture encourages the mould, and it is spread extensively if diseased plants are sprayed with water in the presence of healthy ones. ”

“ Everyone knows that mildew and vermin do damage in the home and in the field, but very few understand that, in addition to these visible enemies of man, there are swarms of invisible plants and animals some of which do far more damage, both directly and indirectly, than the seen and familiar enemies. ”

“ Taylor will think it right to favour you with a statement of the facts, that future "Note"-makers may not perplex future editors with endless "Queries" on the subject.
R.J.
Mildew in Books.—Can you, or any of your readers, suggest a preventive for mildew in books?
In a valuable public library in this town (Liverpool) , much injury has been occasioned by mildew, the operations of which appear very capricious; in some cases attacking the printed part of an engraving, leaving the margin unaffected; in others attacking the inside of the backs only ”

“ It is propagated by spores, which, falling on a silkworm, germinate and penetrate its body. A mycelium is then developed, which spreads throughout the body. Hyphæ appear through the skin, and bear white chalky-looking spores; these become detached, and float in the air as an impalpable dust-like smoke. Damp further develops the fungus.
Insects suffer much from the ravages of fungi. The house-fly sticking to the window-pane is seen to be surrounded by the mycelia of Penicillium racemosum (Sporendonema muscæ, or Saprolegnia feræ) . ”

“ The parasitism of numerous minute species on living and growing plants has its parallel even amongst phanerogams in the mistletoe and broom-rape and similar species. Amongst fungi a large number are thus parasitic, distorting, and in many cases ultimately destroying, their host, burrowing within the tissues, and causing rust and smut in corn and grasses, or even more destructive and injurious in such moulds as those of the potato disease and its allies. A still larger number of fungi are developed from decayed or decaying vegetable matter. ”

“ It is these tubes, and the spores thrown from them, which you see forming a kind of halo round the dead fly as it clings to the pane. Other fungi in the same way kill the silkworm and the caterpillars of the cabbage butterfly. Nor is it only the lower animals which suffer. When we once realise that fungus spores are floating everywhere in the air, we can understand how the terrible microscopic fungi called bacteria will settle on an open wound and cause it to fester if it is not properly dressed. ”