Part 46 (1/2)
==Celery Fly.==--The apparent blisters in Celery leaves are spots deficient of leaf-green, which the larva of the Celery Fly has eaten.
Dusting newly-planted Celery with lime or soot may do something to prevent the fly from laying its eggs, but the most certain preventive is to boil half a pound of coal tar in one gallon of water for twenty minutes, add fifty gallons of clear water, and syringe the plants about noon once or twice from the middle to the end of June. When once the grub has made a home, it should be crushed by pinching the leaf between the finger and thumb, or the injured portions of the leaves should be cut out and burned. In doing this it must always be remembered that the leaves are as much needed by the plant as the roots, and every leaf removed tends to diminish the vigour of the plant. Our ill.u.s.tration shows the Celery Fly (formerly known as =Tephritis onopordinis=, but now called =Acidia heraclei=) natural size and magnified. This fly is also destructive to the leaves of Parsnips, and is named =onopordinis= from its habit of frequenting the Cotton Thistle (=Onopordon Acanthium=). The larva is white to very pale green, the fly is s.h.i.+ning tawny. An Ichneumon Fly detects the larva of the Celery Fly in the Celery and Parsnip leaves, and lays its eggs in the body of the larva. These parasites, named =Alysia apii=, a.s.sist in reducing the numbers of the Celery Fly.
[Ill.u.s.tration: CELERY FLY AND LARVA =Acidia heraclei=]
All Celery refuse should be destroyed by fire. Infested ground may, if suitable, be trenched, bringing the subsoil to the surface and burying the top soil containing the pupae. Frequent rough digging and the exposure of fresh surfaces to be searched by birds will also do something to abate the number of this pest. But in bad cases it will be necessary to resort to gas-lime, which poisons the pupae and eventually benefits the soil, although in the season immediately following its use crops may be less satisfactory than usual.
==Onion Fly.==--Onions are frequently attacked by the larvae of the Onion Fly, and in some instances the entire crop is destroyed. Our ill.u.s.tration shows the natural size of the fly and maggot, with magnified representations of both. The fly lays six to eight eggs on an Onion plant, generally just above the ground. These eggs hatch in from five to seven days, according to the temperature, and the maggots at once burrow into the Onion. The result is soon visible in the discoloration of the leaves which turn yellow and begin to decay.
Several generations of the insect, the scientific name of which is =Phorbia cepetorum=, appear in the course of a single season. A close ally is the Cabbage Root Fly (=P. bra.s.sicae=), the destroyer of Cabbage roots.
[Ill.u.s.tration: ONION FLY AND LARVA =Phorbia cepetorum=]
Among the numerous methods of preventing attack and of destroying the grubs the following are worth attention:--
Where this pest proves very troublesome it may be desirable to transfer Onion growing to new ground until the infested land has been purged of the pupae. Instead of throwing useless Onion material on the waste heap to afford the fly a home for its eggs, every sc.r.a.p should be burned. As the preparation of an Onion bed approaches completion, powdered lime well mixed with soot, in the proportion of two bushels of the former to one of the latter, may be sown evenly over the surface and raked in.
Sand impregnated with paraffin sown along the drills has answered as a preventive. Vaporite is a destroyer of the pupae; this preparation has proved deadly to ground vermin generally. Earthing up the Onions was proved by Miss Ormerod's experiment to be effective. The objection to this procedure is the probability of enlarged necks which are not wanted. An emulsion, composed of one pint of paraffin, one pound of soft soap mixed with ten gallons of water, thoroughly churned by a hand syringe and sprayed over the young plants in a fine mist, is a valuable preventive. The dose may be repeated after rainfall, if necessary. The quant.i.ties named suffice for a small plot only. Soapsuds are destructive to the maggots, disagreeable to the fly, and beneficial to the young plants. The suds should be sprayed over the bed from a watering can on the first appearance of a yellow colour in the gra.s.s. As a final suggestion reference may be made to a singular fact which we do not profess to explain, viz. that transplanted Onions are very seldom touched by grub. The modern practice of raising seedlings under gla.s.s in January or February, and planting out in open beds in April, offers the advantage of a long season of growth combined with comparative immunity from attack by the Onion Fly.
==Turnip Fly,== or ==Flea,== is well known to the gardener, and is the most troublesome of all the aerial pests of the farm, and one with which it is most difficult to cope, not only because of its general diffusion and numbers, but because it produces a succession of broods throughout the summer, and is therefore always in force, ready to devour the crop immediately it appears. The so-called 'Fly' is a small beetle named =Haltica (Phyllotreta) nemorum=, strongly made, and decidedly voracious.
The larvae are not to be feared, except that, of course, they in due time become beetles. In the perfect state this winged jumping insect makes havoc of the rising plant of Turnips, but the crop is only in danger while in the seed-leaf stage. It is in the spring and early summer chiefly that the ravages of these insects occasion perplexity, for they awaken from their winter torpor active and hungry, and have a ready appet.i.te for almost any cruciferous plant. Hence we see the leaves of Radishes pierced by them, and all such weeds as Charlock, Cuckoo Flower, Hedge Garlic, and Water Cress serve them for food until the Turnip crops are on the move, when they will travel miles, even against the wind, to wreck the farmer's hopes. The Cabbage Flea (=Haltica oleracea=) in some districts is equally troublesome, if not more so. Whole Cabbages may be destroyed by this pest, and even Hops are often ruined by it.
[Ill.u.s.tration: TURNIP FLY, OR FLEA =Haltica (Phyllotreta) nemorum= (with larva and chrysalis)]
Preventive and remedial measures that can easily be carried out in a garden may be impracticable on a farm. We propose to enumerate them briefly as they occur to us, leaving the ultimate choice of weapons to those who may unfortunately find occasion to use them.
One precaution is to insure a quick germination of the seed and strong growth of the plant in its seed-leaf stage. The cotyledons are tender and tasty, perhaps sugary from Nature's process of malting; and while the seed-leaf is a.s.sailable the =Haltica= makes the best of the s.h.i.+ning hour. The seed sown should be all of one age, and the newest possible, because of the need for a quick and strong growth. When a powerful artificial is sown with the seed, the quant.i.ty of seed must be increased, as a proportion may be killed by the manure. It is important always to drill Turnip seed; broadcasting seems to invite the Fly--at all events, a drilled crop is generally safer. Before sowing, the seed may be soaked in paraffin or turpentine. Of the two the latter appears to be the more successful in keeping the insects at bay.
Rolling an infested plant disturbs and weakens the insects and stimulates the young plant.
The sprinkling of slaked lime over the seedlings is at once a safe and an efficient process, and possesses the additional advantage of being beneficial to the plant. We are aware that it does not always succeed, but we are inclined to attribute the failure to a bad quality of the lime, or a careless method of employing it. There should be enough put on to make the plants white, and they will be none the worse for the whitening. Dustings of fine ashes or soot are scarcely less effective, but salt must not be used, for it injures the plants and does not hurt the beetle. All such dustings should be done in the early morning, while the plants are wet with dew. To apply a dusting at midday, when the sun s.h.i.+nes gaily, is to waste time, and probably many of the recorded failures might be explained if we knew at what hour and in what sort of weather the work was done. Nets and sticking boards have been tried and found effectual, and yet such things are rarely used. A board thickly covered with white paint, drawn over the plot on a still, sunny day, soon becomes a black board by the myriads of =Halticas= that jump at and remain attached to it, the victims of their extravagant love of light.
Old sacks soaked in paraffin and drawn over the drills impart a disagreeable flavour to the leaves, and a very fine spray of paraffin distributed by a machine specially constructed for the purpose has proved effective.
Finally, this, in common with all other insects in the winged state, needs a dry air and some degree of warmth for its health and happiness.
Many kinds of larvae need moisture, but no winged insect can abide moisture long, and herein is a clue to the eradication of Turnip Fly. By the simple process of spraying the plant three or four times a day, until it is out of the seed-leaf, and the danger is over, it is possible in the garden to wash out the =Haltica=; and any kind of insecticide or flavouring, such as qua.s.sia, may be mingled with the water to render the plants distasteful to the insects.
The ill.u.s.tration on page 422 shows the Turnip Fly in its three stages, and in each case of the natural size and magnified seven diameters.
[Ill.u.s.tration: DADDY LONGLEGS, OR CRANE FLY =Tipula oleracea= (in various stages)]
==Daddy Longlegs==, or ==Crane Fly==, in its perfect form of a fly (=Tipula oleracea=) does no harm, but the grubs, known by the familiar name of 'leather-jackets' owing to the toughness of their skins, are terribly destructive. During late summer and autumn the female fly deposits its eggs in large numbers in turf, in garden soil and amongst garden refuse.
The eggs are hatched in a fortnight or so and the dark grubs lie in the ground through the winter, inflicting their maximum, amount of injury to young crops in spring and early summer. Where song birds are scarce the Tipula is capable of utterly destroying gra.s.s and of seriously ravaging the Kitchen Garden; but cultivation, aided by the robins, thrushes, nightingales, and other birds, will keep the insect within bounds, even after a hot summer favourable to its increase. Where this pest is known to exist, an application of Vaporite at the time of preparing ground for sowing or planting will destroy many of the grubs. The regular use of the hoe is also to be recommended, for by the disturbance of the soil the enemy is exposed to the sharp eye of the robin and other feathered gardeners.
==Root-knot Eelworm.==--One of the worst pests that a Cuc.u.mber-grower has to deal with manifests itself by the presence of minute warts or nodosities, chiefly on the rootlets. These warts, which are caused by the action of innumerable small thread-like worms named =Heterodera radicicola=, range from the size of a pin's head to that of a pea, and when they are present in large numbers the total failure of the Cuc.u.mber crop is the invariable result. The eelworms are probably introduced to Cuc.u.mber-houses in infected water. Each worm is about one-seventyfifth of an inch in length and is at first coiled up inside a transparent egg.
At maturity the eggs crack open, and the worms on emerging bore into the most tender rootlets, and there lay their eggs. These eggs speedily hatch inside the plant and new eelworms are produced, which traverse the rootlets in every direction.
[Ill.u.s.tration: ROOT-KNOT EELWORMS AND EGGS (=Heterodera radicicola=)]
These =Heterodera= are by no means peculiar to the Cuc.u.mber; they attack the roots of Tomatoes and Melons, and the roots, stems, and foliage of many other plants. Our ill.u.s.tration shows some very small Cuc.u.mber rootlets, natural size, with the eelworms in the eggs, and also emerging from and free of the empty eggsh.e.l.l (enlarged eighty diameters).
Immediately symptoms of the pest are apparent from the wilting of the foliage and stems, all infected plants should be removed and burned. The soil must also be cleared out and the interior of the house thoroughly washed with a solution of carbolic acid in water:--one part of the former to eight parts of the latter. To purify the infected soil, use a solution of carbolic acid (one part) and water (twenty parts) and saturate three times, at intervals of a fortnight. Another remedy is to mix weathered gas-lime freely with the soil. In either case the soil will be unfit for use for at least six weeks after treatment. When the house has been well cleansed, fresh compost should be used, to which the addition of lime and soot, mixed with the soil, will be beneficial.
[Ill.u.s.tration: MEALY BUG =Dactylopius odonidum=]
==Mealy Bug.==--This plague is by no means confined to plants under gla.s.s.