The Culture of Vegetables and Flowers From Seeds and Roots / 16th Edition

by Sutton & Sons Ltd.

CARROT FLY
Psila Rosæ (with maggot and chrysalis)

It is well to dig the ground in autumn, so that the earth may be exposed to the frosts of winter and the pupæ to the attention of birds. After sowing, spray the Carrot bed with paraffin emulsion. Spray again after germination, and a third time when thinning is finished. The emulsion to be made by dissolving half a pound of soft soap in a gallon of boiling water. While still boiling, pour the liquid into two gallons of paraffin and churn thoroughly until a buttery mass results. This will keep for a long time in tins. Before use, dilute with twenty times the quantity of water—soft water if possible. This is an excellent preventive. After the work of thinning, the fly may also be kept off the plants by scattering over them ashes, sand, or earth, impregnated with paraffin. Carbolic powder and soot are both disagreeable to the insect. It has been observed that when singling the disturbance of the soil is favourable to the operations of the Carrot Fly. A copious watering when the task is ended will firm the earth round the remaining roots, and prevent the fly from easily getting down to deposit eggs.

Carrots and Parsnips are often attacked by the larva of a Carrot Moth (Depressaria cicutella), which spins webs for security while feeding, and sometimes works havoc among the foliage. A simple remedy is to shake the caterpillars from the leaves of the plants, when they can be destroyed by the use of lime.

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 illustration 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 shining 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, assist in reducing the numbers of the Celery Fly.

CELERY FLY AND LARVA
Tephritis onopordinis

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 pupæ. 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 pupæ 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 larvæ of the Onion Fly, and in some instances the entire crop is destroyed. Our illustration 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. brassicæ), the destroyer of Cabbage roots.