Part 47 (1/2)
==Wireworm== is the most persistent and destructive of all the ground vermin. There are fully a dozen species of beetles the larvae of which are known as 'Wireworms,' and of these the 'Spring-Jacks,'
'Click-Beetles,' and 'Blacksmiths'--=Elater obscurus, E. lineatus=, and =E. ruficaudis=--are the most prevalent. The female beetle deposits her eggs in the earth in the height of the summer, and in due time the worms emerge and commence their depredations. These worms have a tenure of three to five years in their subterranean homes, during which time they feed voraciously, and are not very particular as to what they eat. Their muscular power renders them expert in burrowing, and they are well protected by their h.o.r.n.y jackets. When their term of feeding is completed, they descend to a considerable depth and change into the chrysalis state, from which they come forth as jumping beetles in the course of July and August, a certain proportion remaining in the ground to complete their final change in spring. Their power of destruction is then at an end. They resort to flowers, lead a merry life for a short time, and when they pa.s.s away leave plenty of eggs to continue the race of Wireworms.
For practical purposes the Wireworm may be regarded as inhabiting every kind of soil and consuming every kind of crop. The crops it is most partial to are Gra.s.s, Potatoes, Turnips, and the juicy stems of all kinds of cereals. The larvae may be trapped by burying in the ground pieces of Potato, or better still thick slices of Beet root; the spots to be marked, and the traps examined every few days, when the Wireworms can be destroyed. Superphosphate sown along the drills with seed has saved spring-sown crops from destruction; and Vaporite, a proprietary article, has also been used with marked success. The latter gives off a gas smelling of naphthalene which kills the Wireworms. Soot is a well-known remedy, and by its use the crops are also benefited.
==Woodlice== are very destructive but easily caught, and they may be completely eradicated by perseverance. When a frame or pit is infested, they can be destroyed wholesale by pouring boiling water down next the brickwork or the woodwork in the middle of the day. If this procedure does not make a clearance, recourse must be had to trapping. In common with Earwigs, they love dryness, darkness, and a snug retreat; but while a mere home suffices for Earwigs, a home with food is demanded by Woodlice. Take a thumb pot, quite dry and clean. In it place a fresh-cut slice of Potato or Apple, fill up with dry moss, and turn the whole thing over on a bed in a frame or pit. Thus you have devised a Woodlouse trap, and next morning you may knock the vermin out of it into a vessel full of hot water, or adopt any other mode of killing that may be convenient. Fifty traps may be prepared in a hundred minutes; and those who are determined to get rid of Woodlice may soon make an end of them.
==Rats and Mice==.--Traps are efficient while they are new, and almost any reasonably good contrivance will answer for a time, but will fail at last, or at least for a season. To keep down Rats and Mice effectually there must be invented a succession of new modes of action, for these creatures--Rats especially--are so clever that they soon see through our devices, which then fail of effect. Generally speaking, two rules may be prescribed. In the first place it is imprudent to fill up their holes or stop their runs; let them have their way. If you stop them, they will make new thoroughfares, to the further injury of the foundation; and, besides, when you are acquainted with their runs, you know where to put traps and poison for the vermin. As to the best poison, there is nothing so effectual as a.r.s.enic; but it should be employed with great care, and before it is brought on the premises the question of safe storage must be considered. A fat bloater split down and well rubbed with common white a.r.s.enic will kill a score of Rats, provided only that they will eat it. Cut it into four parts, and place these in or near their runs, and cover with tiles or boards to prevent dogs and cats obtaining them.
If this fails, try bread and b.u.t.ter dressed with oil of rhodium and phosphorus. The oil of rhodium seems to possess an irresistible attraction for these vermin. When dry food is preferred, there is nothing so good as oatmeal; and it is a golden rule to feed the Rats for a few days with pure oatmeal, and then to mix about a fourth part of a.r.s.enic with it. Several proprietary articles are offered for the destruction of Rats. Before resorting to these means of annihilating vermin it is necessary to take steps to prevent the bodies from proving a nuisance after death. A good fox-terrier will keep a large garden free from Rats and Mice.
THE FUNGUS PESTS OF CERTAIN GARDEN PLANTS
Many of our garden plants are liable to the attacks of fungi. Cures are in most instances unknown, but in some cases preventives--which are better--have been adopted with partial or entire success. Plants raised from robust stocks, grown in suitable soil and under favourable conditions, are known to be less liable to disease than seedlings from feeble parents, or those which have been rendered weakly by deficiencies in the soil or faulty cultivation. Whether weakness is hereditary, or is attributable to a bad system, the fact remains that disease generally begins with unhealthy specimens, and these form centres of contamination from which the mischief spreads. It is, therefore, important that seed from healthy stocks should be sown, and that a vigorous const.i.tution should be developed by good cultivation.
==Anbury, Club, or Finger-and-toe==.--The disease known by these various names is common in the roots of cultivated cruciferous plants such as Cabbages, Kohl Rabi, Radishes, Swedes, Turnips, &c., and also in many cruciferous weeds, including Charlock and Shepherd's Purse. The cause of this disease is an extremely minute fungus, which may lie dormant in the soil for several years for want of a comfortable home, and when a cruciferous plant becomes available the fungus fastens on the fine roots, multiplies rapidly in the tissues, and produces malformation and decay. After the disease has made some progress insect agency frequently augments the mischief, so that on cutting open a large decaying root it is not unusual to find the interior packed with millipedes, weevils, wireworms, and other ground vermin.
Unlike the Potato disease, which spreads from plant to plant through the atmosphere, the fungus of Finger-and-toe infects the ground, and from the first spot attacked the disease spreads rapidly in all directions and in various ways. It may be carried by the soil adhering to implements or the boots of labourers. And each patch becomes a new centre of infection which is spread by digging or raking. Every sc.r.a.p of infected soil, or of diseased fibre which may be added to the manure-heap, distributes the virus over a wider area, so that Finger-and-toe may suddenly appear in parts of the garden which have hitherto been free from this troublesome pest. A very simple experiment will prove the certainty and ease with which the spores may be introduced to fresh land. Macerate the tissue of old Finger-and-toe in water; use this on young isolated plants of Cabbage or Turnip and in a short time the plants will be infected.
The fungus which produces Finger-and-toe is known as =Plasmodiophora bra.s.sicae=, and it belongs to the =Myxomycetes=, or ?slime-fungi,' which, as a rule, live upon decaying vegetable material. The protoplasm of the fungus ramifies among and within the tissues of the roots of attacked plants, and eventually produces an amazing number of spores so small that more than thirty millions would be required to cover a superficial inch. A microscope of great power is necessary to reveal them to human vision.
[Ill.u.s.tration: FUNGUS OF FINGER-AND-TOE DISEASE =Plasmodiophora bra.s.sicae=]
The spores are capable of resting in a state of vitality for a long time, and can easily withstand the frosts of winter. The ill.u.s.tration shows at A the fungus in its protoplasmic condition, and at B its ultimate sporiferous or 'seed'-producing stage, after the protoplasm has changed to a ma.s.s of minute spores (enlarged five hundred and twenty diameters). When a spore in due course germinates, its protoplasmic contents escape through a small aperture in its wall and begin moving about of their own accord in a slow writhing manner. The movement is so much like that of the microscopic animal organism found in ponds, and called =Amba=, that this tiny ma.s.s of moving protoplasm is called =Myxamba=, to denote that it is an amba-like form produced by one of the =Myxomycetes=. Each myxamba is drawn out at one spot into a fine delicate tail or cilium, as at C, D, E, and is capable of a creeping motion in moisture. When quite free from the spores, transparent expansions or limbs extend from the bodies of the myxambae, as at F, G, and when these organisms, after existing in the soil for a longer or shorter time, reach the roots of cruciferous plants, which they apparently enter through the root-hairs, they again a.s.sume the protoplasmic condition shown at A, and live within the cells, at the expense of the nurse-plant. Other cruciferous plants are less seriously damaged by the pest than are Turnips and Cabbages; but it is evident that if diseased Charlock is near Turnips, the latter are very likely to fall a prey to the disease. We advise the sowing of the best seeds, the eradication of cruciferous weeds, and the destruction by fire of all decaying Finger-and-toe material, for it is in this material that the spores of the disease rest ready for continuing the disease in the following season. It is also desirable that cruciferous plants should not be continuously grown in the same quarter--in other words, it would be prudent after an attack of Anbury not to repeat a cruciferous crop on the same ground, but to follow on with a crop of some other cla.s.s.
Numerous experiments have shown that slaked lime can be relied on to destroy the spores of Finger-and-toe in infested land. An application of from fourteen to twenty-eight pounds per pole may suffice in the case of light soils, but fifty-six pounds per pole will not be too much on heavy land, and the dressing should be given either six or eighteen months before a Cabbage or Turnip crop is sown; the longer period is the more certain in its effect. Preference should be given to stone or rock lime over chalk lime. The former is much more powerful and efficient. It may be necessary to repeat the dressing twelve months after the first application. As regards the occurrence of Anbury in seed-beds, frequent transplantation is a very effectual mode of stopping its progress, for the little galls can be pinched off by the workman, and burned as he proceeds; and the plant, being invigorated by change of soil, will soon grow away from the affection. In transplanting Cabbages it is a good plan to discard and burn such plants as are obviously affected with Anbury. It is worthy of remark that in market-gardens this disease is by no means so prevalent as to interfere with the routine of cultivation, although the Cabbages, Broccoli, and Cauliflowers grown in these grounds are, under other circ.u.mstances, especially liable to attack. By 'other circ.u.mstances' we mean that market-gardens are generally kept under high cultivation, the land being perpetually turned and heavily manured; and these measures appear to be a preventive of Anbury, while they result in heavy crops. But on land less energetically tilled Anbury may prevail to such an extent as to interfere seriously with the order of cropping. Another very important mode of keeping down the pest consists in burning instead of burying the stumps and all other refuse of the crop that cannot be turned to account.
Confusion may be prevented if we point out that Club-root, Anbury, or Finger-and-toe--whichever name may be used--is quite distinct from an apparently similar malformation of the root which is sometimes induced by certain characteristics of soil, seed, or manure, and is in fact a case of reversion to the original wild type. Instead of a shapely, solid Turnip, the bulb is divided into a number of coa.r.s.e, worthless tap-roots, caused by either poverty of the soil, careless cultivation, or a degenerated stock of seed. Those who save their own seed continuously for years are almost certain to become well acquainted with this malady. They will find a change of seed necessary, and at the same time an alteration in the routine of culture. A healthy, vigorous plant, derived from a pure seed-stock, does not easily make Finger-and-toe, but a sound root that stands for food and money.
'Grub.'--The wart-like growths formed upon the roots of Turnip and Cabbage by the little hard beetle known as the Turnip-gall Weevil, =Ceutorhynchus pleurostigma=, are also quite distinct from Finger-and-toe. By cutting across a malformed root of Turnip or Cabbage it is usually not difficult to determine the cause of the mischief. If it is Finger-and-toe the root will be found filled with decaying matter; in the case of Weevil attack the small legless maggots, commonly called 'Grub,' will be brought into view; and if it is merely an instance of reversion the cut root will appear to be healthy.
==Potato Disease==.--The fungus which causes the Potato Disease, or 'Blight' as it is sometimes called, was formerly known as =Peronospora infestans=; now it is recognised by scientific authorities as =Phytophthora infestans=. The mark of its pestilent touch on the foliage, and its destructive effect on the tubers, are unfortunately too familiar in gardens and on farms. In dry seasons its energies are restricted, but the scourge is never absent, and during wet summers the parasite may do its deadly work on such a vast scale as to cause a Potato famine. Moisture is a necessity of its existence, and in rotting haulm, decayed tubers, and damp soil the spores remain in a resting condition until they are afforded an opportunity of multiplying with the marvellous rapidity that invests the disease with its terrible power. A series of six ill.u.s.trations, five of which are highly magnified, will enable the reader to follow the development of =Phytophthora infestans=.[1]
[Ill.u.s.tration: No. 1]
The ill.u.s.tration No. 1 shows a Potato leaf on a reduced scale disfigured by the attack of the fungus. The =Phytophthora= is sending mycelial threads (called hyphae) in all directions through the substance of the leaf, feeding on the protoplasm of the cells and destroying the chlorophyll, or leaf-green, in those cells.
[Ill.u.s.tration: No. 2]
[Ill.u.s.tration: No. 3]
No. 2 shows the fungal threads at work. In a diseased Potato plant these threads, or mycelial hyphae, make their way through the substance of the leaves, and down the haulm into the tubers, from which they consume the food stored there.
No. 3 exhibits the various stages of germination of one of the conidia of =Phytophthora infestans=: (=a=) the ripe conidium in water; (=b=) protoplasmic contents breaking up into blocks, which separate and escape (=c= and =d=) as minute kidney-shaped zoospores (=e=) each with two cilia; (=f= and =g=) the zoospore coming to rest and losing its cilia; (=h=, =i=, =j=, and =k=) successive stages of germination of the zoospore.
[Ill.u.s.tration: No. 4]