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 larvæ 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 quassia, may be mingled with the water to render the plants distasteful to the insects.
The illustration on page 422 shows the Turnip Fly in its three stages, and in each case of the natural size and magnified seven diameters.
DADDY LONG LEGS
Tipula (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 grass 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 Cucumber-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 Cucumber crop is the invariable result. The eelworms are probably introduced to Cucumber-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.
CUCUMBER EEL-WORMS AND EGGS
Anguillulæ
These Heterodera are by no means peculiar to the Cucumber; they attack the roots of Tomatoes and Melons, and the roots, stems, and foliage of many other plants. Our illustration shows some very small Cucumber rootlets, natural size, with the eelworms in the eggs, and also emerging from and free of the empty eggshell (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.