ONION FLY AND LARVA
Anthomyia ceparum
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 pupæ. Instead of throwing useless Onion material on the waste heap to afford the fly a home for its eggs, every scrap 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 pupæ; 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 quantities 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 grass. 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 glass 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 aërial 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 larvæ 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 appetite 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.
TURNIP FLY OR BEETLE
Haltica 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 assailable the Haltica makes the best of the shining 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 quantity 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 shines 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.