THE HESSIAN FLY.
The following suggestions have been prepared by Mr Charles Whitehead, F.L.S., F.G.S., at the request of the Lords of the Committee of Council for Agriculture, for the information of agriculturists:
The Hessian fly is terribly destructive to corn crops in the United States, Canada, and parts of Germany. In some years it has almost entirely destroyed the wheat crops in large districts in these countries. In the upper counties of Georgia Packard States ‘the fly has committed such ravages upon the wheat as scarcely to leave enough seed for another year.’ It had not been found in Great Britain until this present year, though in 1800 fears were entertained that it had been introduced. In 1788 the importation of wheat from America was prohibited by the British government until it was ascertained that it was not likely that the insect could be brought over in this way. Now, however, without any doubt it has appeared here, and all effort must be made, and at once made, to stamp out this dangerous intruder. To effect this, if possible, information is given below as to the nature of the attack of the Hessian fly, and a description of it in its various stages, as well as methods of preventing it from spreading in this country.
The plants of wheat and barley infested with this insect turn yellow, and become stunted and unhealthy. Plants upon sharp gravelly patches, ‘pinnocky places,’ ‘stone-brash,’ or ‘stone-shatter,’ and upon the poorest parts of fields, show the attack first and most seriously. As the plants ripen, the straw becomes root-fallen and scrawled, the ears are small, and the grains misshapen and shrivelled. Corn-plants thus affected should be carefully examined, especially their leaves or blades, just at the points where they cover the second points of the stems from the ground. Upon corn-plants thus injured, either the larvæ of the Hessian fly or its pupæ will be found close to the lower joints between the stems and the leaves or blades. The larvæ, which are the authors of the mischief, as they suck out the juices of the plants, are clear, white, or translucent maggots about the fifteenth of an inch long, having stripes of a greenish hue under their skins. They remain in this state from four to six weeks, and then assume the pupal or semi-pupal form. The pupæ are called ‘flax-seeds’ in America, because they are like small elongated flax-seeds. They are a little longer than the larvæ, and are of a chestnut colour. It is in this state alone that the Hessian fly has been seen in England. These pupæ are unmistakable, and when once discovered, immediate steps should be taken to prevent them from transforming into flies, which would lay eggs upon the corn-plants either in the coming autumn or in the spring.
Crops of wheat and barley in whose straw the ‘flax-seeds’ have been found should be cut above the second joint, either by setting the reaping-machines high, or by reaping them by hand, so as to leave a long stubble. Where barley is short and must be cut with scythes, the mowers should be instructed to keep them as high as possible. Land upon which the crops have been infested should be cultivated or broad-shared immediately after harvest. The stubble and rubbish should be collected most carefully and burnt; after this the land should be deeply ploughed, or the stubble might be ploughed in at once deeply. Straw from infested fields should be closely inspected when thrashed. If pupæ are found, the straw should be used on the spot if possible for litter, and all passed through ‘mixens,’ that heat may destroy them. The chaff and ‘cavings’ from such straw should be burnt, and the corn screened in the most careful manner. Corn from infested fields should on no account be used for seed. Where manure is obtained from the cow-sheds and stables of London and other cities and towns, it should be ‘mixened’ for some time, as it is very probable that the pupæ of the insect might be imported in packing-cases and with straw crates from America and Canada. Wheat-plants and barley-plants that show yellowness and other signs of disorder in the autumn or spring should be closely examined for larvæ or pupæ of the Hessian fly. Should it be discovered that the larvæ or maggots are injuring young wheat-plants in November, or that pupæ—‘flax-seed’—are present upon these, it would be well to feed them down hard with sheep.