THE CULTURE OF VEGETABLES AND FLOWERS FROM SEEDS AND ROOTS TEXT

Spraying Potato plants twice or thrice with Bordeaux mixture has proved effective in warding off the attack of _Phytophthora infestans_, and the practice is now freely adopted, especially in humid districts. The first application should be given towards the end of June or early in July, immediately the haulm is sufficiently developed. The Bordeaux mixture is made in the proportion of four pounds of pure copper sulphate and two pounds of quicklime to forty gallons of water. The foregoing quantities will give what is known as the _one per cent._ mixture. For the _two per cent._ mixture the quantities of copper sulphate and quicklime must be doubled, but the amount of water should remain at forty gallons. In its effect on the fungus, however, little difference is to be found between the two solutions. The copper sulphate is stirred into a few gallons of hot water placed in a wooden tub or earthenware vessel. When quite dissolved, add twenty or thirty gallons of cold water. The lime, which must be freshly burnt quicklime, is then slaked in another vessel and thoroughly stirred with two or three gallons of water until it is of the consistency of thin cream. As soon as the liquid is quite cold, filter it through coarse sacking into the copper sulphate solution and add water to make a total of forty gallons. To be effective, Bordeaux mixture must be applied in the form of a fine spray, and not with a coarse-holed syringe. The Burgundy mixture, the use of which is preferred by some, acts in a very similar manner to the Bordeaux mixture, and is made in the same way as the latter, except that washing soda (five pounds) is substituted for quicklime. Those who leave Potatoes to rot in the ground because the crop is not worth digging, or who bury diseased haulm and tubers in a shallow trench, under the impression that it is a safe way of getting rid of worthless vegetation, are simply storing _Phytophthora_ for another attack in the event of Potatoes being planted in the same land again. If buried at all, it must be at a considerable depth, but the effectual method is to destroy all Potato refuse by fire. Wart Disease (Black Scab) of Potatoes (_Synchytrium endobioticum_, Percival).—This extremely infectious and destructive disease of the Potato has been given a variety of names in different parts of the country, but it is now generally known as the Wart or Cauliflower Disease, the latter term being attributable to the Cauliflower-like appearance of the outgrowth of the fungus. This outgrowth first shows in the eyes of the young Potato in the form of small wrinkled warts. These multiply and combine, thus creating a dark spongy scab which eventually decomposes. Where the disease is very rife it attacks haulm as well as tubers, and a yellowish-green mass may sometimes be found just above or just below the surface of the soil. As a rule, however, no outward indication of its existence is to be seen in the crop during the early stages of growth, but towards the end of the season the haulm of badly diseased plants often retains a fresh green appearance when the foliage of others, which are healthy or only slightly attacked, is dying off. Infection is perhaps most commonly spread by the planting of diseased tubers. Another frequent means of dissemination is caused by consigning infected haulm to the waste heap instead of to the fire. The spores may also be introduced in manure from animals fed on diseased Potatoes in a raw state, and they may even be carried from one plot to another on garden implements or the boots of those who walk across infected ground. Immediately any sign of the disease is observed it should be dealt with promptly and in no uncertain manner. Every particle of the infected material must be carefully collected and burned. Dig out the soil around all diseased plants and burn this also. On infected land it is important that some crop other than Potatoes be taken in the season following the outbreak, and, if possible, such land should not be used for Potatoes for at least five or six years. But where garden space is limited, a contaminated plot may have to be requisitioned for Potatoes within two or three years. In such cases it is an excellent plan to dust the sets freely with sulphur at the time of planting and to repeat the application before earthing up. Although for some years the unremitting labour of experts has been devoted to the investigation of Wart Disease, and innumerable experiments have been undertaken, no effectual remedy has yet been discovered. It has been found, however, that certain Potatoes are resistant to the disease, and by order of the Ministry of Agriculture and Fisheries none but ‘immune’ varieties may be planted in districts scheduled as infected areas. A notification of the existence of Wart Disease must be made to the Ministry immediately it is observed. Leaf Spot of Celery.—This disease, which is caused by a minute fungus (_Septoria apii_, Chester), is capable of inflicting serious damage to the Celery crop unless prompt measures are taken to exterminate it. The first sign of its appearance is to be found in the leaves in the form of small brown patches. These are, however, quite distinct from the spots deficient of leaf-green due to the attack of the Celery Fly larvæ, and on close examination may be recognised by the presence of a number of very small black points. From the leaves the fungus quickly spreads over the leaf-stalks and finally to the heart of the plant, ending in its total collapse. So rapid is the multiplication of the spores, especially in moist weather, that a few diseased plants are capable of infecting a large plot within two or three weeks. Immediately discoloration of a leaf is noticed the affected portion of the plant should be picked off. If the stage of the disease is so far advanced that the outer leaf-stalks have become decayed, the entire plant should be removed and destroyed. It is of the utmost importance that every particle of diseased material be consigned to the fire and not to the waste heap. Spraying three or four times with Bordeaux mixture at intervals of two or three weeks may be helpful in the case of a light attack, but the safest course always is to remove and destroy any plant on which the fungus is found. One of the most frequent means of introducing Leaf Spot of Celery is through the use of infected seed, and therefore only seed which has been treated for the destruction of the fungus should be sown. Lettuce Mildew.—This fungus is named _Bremia lactucæ_, formerly known as _Peronospora ganglioniformis_, and is sometimes of the most destructive character. It covers Lettuce leaves with a fine white bloom, which decomposes the leaves, and makes them adhere together in one putrescent mass. It should be looked for in its earliest stages, and be hand-picked and burned. Old Lettuce stumps should likewise be pulled and burned, otherwise they may harbour the disease. Onion Mildew is caused by the fungus _Peronospora Schleideni_, which is occasionally disastrous in its effects, more especially in cold, wet seasons. It occurs at uncertain intervals of time with extraordinary virulence, and then utterly destroys the crops. Autumn sowing is considered a good preventive by many growers, as the disease is frequently fatal to spring seedlings. In its early stages the mildew may be successfully dealt with by freely dusting the plants with flowers of sulphur when wet with dew, or by the application of sulphide of potassium in the proportion of one ounce to a gallon of water. Otherwise all diseased material should be removed and burned. Pea Disease.—Although garden Peas often suffer badly from the attacks of _Peronospora viciæ_, which is the cause of Pea Mould, yet the most deadly foe to Peas, especially late Peas, is a fungus of a totally different character. To such an extent does the Pea Blight sometimes devastate the later Peas, particularly in dry summers, that the whole crop is in some gardens completely annihilated. The name of the fungus of the Pea Blight or Mildew is _Erysiphe Martii_. Its attack is often made suddenly; the leaves then lose their natural green colour, and become yellowish and densely coated with a fine white bloom; this bloom becomes at length dusted over with innumerable minute black bodies, which look, under a lens, like tiny spiders’-eggs in the web. These little black bodies are filled with extremely small transparent vessels, and each vessel contains from four to eight spores or seeds. Our illustration shows this _Erysiphe_ enlarged one hundred diameters, with two of the vessels containing the spores removed from the globular spots and further enlarged. The only safe way of dealing with infested Pea plants is to burn them. Many other species of fungi belonging to the same genus attack fruit trees, vegetables, and garden flowers. It is, however, unnecessary to illustrate them, as they more or less resemble the fungus of Pea Blight. They all arise from an _Oïdium_ condition, similar to the _Oïdium_ or Mildew of the Vine, and it is in this condition alone, as in the case of the Vine, that they can be reached by any fungicide. [Illustration: Fungus of Pea] FUNGUS OF PEA MILDEW _Erysiphe Martii_ Tomato Diseases.—The Tomato, like its near relative, the Potato, is subject to a number of destructive diseases which spread rapidly if allowed to become established. The most serious of these epidemics are found among crops cultivated under glass, where the forcing treatment which they often receive, and the soil and atmospheric conditions, render the plants abnormally susceptible to the attacks of fungi and insect pests. Perhaps the most virulent forms of disease with which the Tomato-grower is troubled arise from the attacks of parasitic fungi and bacteria, among which the following are most frequently met with:— SLEEPY DISEASE, or TOMATO WILT.—In its outward symptoms and effects this disease somewhat resembles an attack of Root-knot Eelworm, but the swellings are absent from the root. The plants for a time appear quite vigorous and healthy, but when full-grown they suddenly wilt and die within a few days. The malady is caused by the fungus _Fusarium lycopersici_, which first invades the roots and ultimately eats its way through the substance of the collar or stem near the surface of the soil, in consequence of which the supply of water taken up by the roots is cut off from the leaves above ground and the plant collapses. There is no remedy for the Sleepy Disease of Tomato, and plants which bear evidence of infection should be carefully dug up and burned. TOMATO ‘STRIPE.’—This disease of the Tomato is comparatively common, and although the attacks are sometimes slight its ravages may be disastrous when conditions are favourable for its development. The presence of Tomato Stripe is usually first noticed about the time fruit is forming. The stems of the diseased plants then exhibit dark spots and elongated sunken stripes of a brown tint, and yellow patches, which turn brown later, appear on the leaves. Brown pits or depressions develop on the fruits and spoil their appearance. The disease has been traced to the action of a bacterium which closely resembles, or is identical with, that causing Stripe among Sweet Peas. This organism probably resides in the soil, and the signs of its attack are often visible in young plants. In severe cases the soil of the house should be removed and replaced with fresh loam. But when only slight traces of the disease are apparent, partial sterilisation of the soil by means of carbolic acid, as recommended for Root-knot Eelworm on page 425, may be adopted. One of the surest means of guarding against losses by Stripe disease, is to promote robust healthy growth, and to avoid extreme forcing conditions, particularly by the excessive use of nitrogenous manures. Where, however, forcing manures may have been employed in too large a quantity, an application of potash (in the form of kainit or sulphate of potash) and phosphatic fertilisers should be given to counteract the effect of the nitrogen. Immediately any trace of the disease is found, remove the affected part of the plant, if it is possible to do so without serious injury, but otherwise the entire plant should be uprooted and destroyed by fire. It should be remembered that the organism can be carried on the fingers and on tools, and therefore knives with which affected plants have been trimmed should be sterilised with lysol or some other antiseptic solution before being used on healthy plants. 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. Judicious management in air-giving, which is one of the fundamental principles of successful Tomato culture, will do much to prevent the attack of _Cladosporium fulvum_. Under regular examination the presence of the disease will be revealed before considerable damage can be inflicted, and when only a few leaves are affected, carefully remove and consign them to the fire. Spraying with the Bordeaux mixture at half the usual strength is recommended when the disease is first noticed. When the plants are bearing flowers or fruit, fungicides containing copper must not be used, but a solution of liver of sulphur, one ounce dissolved in six gallons of water, employed instead. ROOT-KNOT EELWORM.—A dangerous insect pest which frequently attacks the Tomato, in common with the Cucumber and Melon, is the Root-knot Eelworm (_Heterodera radicicola_). The root on which the swollen pea-like knots develop do not carry on their ordinary functions, and the leaves droop, the stem becomes limp, and the whole plant soon collapses and dies if the trouble is severe. The treatment suggested on page 425 should be adopted. Sometimes the outdoor Tomato crop is attacked by _Phytophthora infestans_, the fungus responsible for the Potato Disease: Bordeaux mixture should be used to check it. Directions for preparing the Bordeaux mixture are given on page 440. Another useful preparation which checks many fungus diseases may be made by dissolving one ounce of potassium sulphide (liver of sulphur) in three or four gallons of water, to which should be added an ounce or two of soft soap. The last named greatly assists in the complete and uniform wetting of all parts of the foliage. THE FUNGUS PESTS OF CERTAIN FLOWERS Cineraria and Senecio Disease.—_Senecio pulcher_, soon after its introduction into England, was attacked, and in some gardens completely destroyed, by a fungus named _Puccinia glomerata_, or rather the _Uredo_ stage of this fungus with simple, not compound, spores. The fungus is well known, being closely allied to that which causes the rust or mildew of corn crops. It is very common on the wild species of Groundsel in England, being especially frequent and virulent on the Ragwort Groundsel, _Senecio Jacobea_, from August to October. The leaves of infected plants are covered with rust-coloured dusty pustules, the _Uredo_ condition of the fungus, and known in this stage as _Uredo senecionis_, sometimes termed _Trichobasis senecionis_. The fungus has a _Puccinia_ stage of growth very similar to that of the Hollyhock fungus, _Puccinia malvacearum_. [Illustration: Fungus of Senecio Disease] FUNGUS OF SENECIO DISEASE _Uredo senecionis_ At A is illustrated a fragment of a leaf of _Senecio pulcher_, natural size, and covered with the orange-coloured fungus; at B a small part of a _Uredo_ pustule as seen bursting through the cuticle of the Senecio leaf. No remedial measures for the extirpation of this fungus are known, but as garden Senecios and Cinerarias are infected by diseased plants of Wild Groundsel, it is desirable that plants of the latter (especially when diseased) should be destroyed. Weeds in and about gardens are a common cause of disease in cultivated plants. It often happens that a weed, being sturdy, is only slightly inconvenienced when attacked, whilst a cultivated plant will speedily succumb if attacked by the same fungus. This is the case in the _Sempervivum_ disease. In this country the common House Leek is the nurse-plant, and is seldom much injured; but if the disease _Endophyllum sempervivi_ gets among greenhouse species, every plant may be utterly destroyed. [Illustration: Fungi of Gladioli, Lilies, etc.] FUNGI OF GLADIOLI, LILIES, ETC. _Urocystis gladioli_ and _Ovularia elliptica_ Gladiolus, Crocus, Narcissus, and Lily Diseases.—In certain soils and situations where the ground is heavy and the atmosphere inclined to be humid the Gladiolus is very subject to a destructive fungoid disease. This is especially the case during unusually wet summers. The disease attacks the corm, and corrodes and decomposes the tissues, so that on cutting open a corm the whole interior, or such parts as are diseased, will be found permeated with a deep, foxy colour. It is believed by some persons that one stage of this disease is identical with the disease named ‘Tacon’ by the French, and in this country known as ‘Copper Web,’ _Rhizoctonia crocorum_. This _Rhizoctonia_ is a mere spawn or mycelium, a mass of rusty-brown material like a thick coating of spider’s web of a red tint. This parasite attacks the Crocus (especially _C. sativus_), the Narcissus, Asparagus, Potato, and other plants. Immersed in the softer and damper portions of the red substance of the corm may frequently be found great numbers of large compound spores, as illustrated at A (enlarged two hundred and fifty diameters). These bodies belong to the fungus named _Urocystis gladioli_; but whether they really belong to the spawn named _Rhizoctonia_ there is no conclusive evidence, as the spores have never been seen on the threads or upon any spawn. The spores are very ornamental objects, consisting of from three to six compacted inner brown bodies, surrounded by an indefinite number of transparent cells. At maturity these spores break up as at B, and are the means of reproducing the fungus. The Colchicum is attacked by a closely allied but different species of _Urocystis_—viz. _U. colchici_. The Ranunculaceæ are attacked by another ally in _U. pompholygodes_ and Rye is attacked by a third in _U. occulta_. No method of cure has yet been published for this pest; it is, however, desirable that only sound and good corms should be planted, for if infected corms are placed in the ground it is one certain means of propagating the disease. The bars shown across the illustration of this disease are magnificent crystals, very common in Gladiolus corms. Lilies are very subject to a disease in early summer: the leaves get spotted and damp, and rot off; the flower buds speedily follow, and leave the bare stalk. The disease of Lilies is caused by a fungus closely allied to the fungus of the Potato disease, and named _Ovularia elliptica_, known also as _Botrytis elliptica_ (see illustration C). The spores are large, and produce zoospores, or spores with hair-like tails (cilia), capable of swimming about in water or upon moist places. This pest attacks a large number of species of _Lilium_, both before and after flowering. _Hyacinthus candicans_ and some Tulips suffer from a very similar, if not the same, organism. This fungus has been described as a true _Peronospora_. Bulbs are subject to many fungus growths as _Volutella hyacinthorum_, _Didymium Sowerbei_, &c.; many fungi follow the decay of the bulb, others undoubtedly produce or