THE HESSIAN FLY.

Ashburton Guardian, Volume VII, Issue 1778, 1 March 1888, Page 3

THE HESSIAN FLY.

Thk appearance of this scourge to farmers m several localities m the North Island, whence it is almost certain eventually to find its way south, renders it desirable that agriculturists should make themselves acquainted with the appearance of the insect, so as to be able to recognise it immediately upon its advent, and also with the best method of dealing with it effectually. As to the first point a London paper supplies the following information, a careful study of which should enable anyone easily to identify the insect on sight. It says : — " The presence of the fly is usually first discovered by the plants m the corr field presenting- the appearance of a disease well known to agriculturists as root-falling, or gout, m the stems. Close inspection leads to the discovery rt of strange dark-colored objects packed j tightly between the outer coverings, or j protecting blades, and the knots of the

second joints above the root 3of the plants." These objects are the pupw of the Hessian fly, which, from their remarkable resemblance to grains of linseed, are known across the Atlantic as "flax-seeds." The fly itself, which emerges from the " flax-seed," is about an eighth of an inch m length, with a wing expanse of about a quarter of an inch. The color of the body is dark brown, aud on the thorax it is nearly black. The wings are of a transparent dusky grey tint, and are fringed at the j edges. It is frequently mistaken for, the wheat midge (Cecidomyia tritioi),

but the latter is of an orange yello

color, with the joints of the antennae less hairy. Each female Hessian fly lays from 80 to 100 eggs, and places from 20 to 40 upon a single leaf m the creases of the upper parts of the blades of the young corn plants. The eggs are quickly hatched, taking from four to eight days, according to the weather. From the egg laid m tho spring comes a wrinkled, yellowish maggot -the larva — without legs, having 14 joints. It is close upon the eighth of an inch m length when full grown, being then of a clouded white hue, and showing faint greenish lines under the skin. After the larva has been hatched it almost invariably proceeds from its birth-place to the second joint of the stem, at the base of the blade, or leaf, and absorbs the juices of the plants. After about five or six weeks the larva, still m its position close to the second joint of the plants, gradually puts on a bright chestnut color, and at this time, or shortly afterwards, casts this embrowned skin. The skin is not cast m the ordinary meaning of the term, as the larva remains within it contracted m size and free to move. This is the flax-seed stage. The larvro m these puparia are fixed so very tightly m the straw, which has ripened and hardened around them, that it is frequently difficult to extract them from it. The pupa eventually breaks open and crawls from its puparium and works its way upwards within the sheath of the leaf until it arrives at some cleft m the now dead aud brittle straw ; through this cleft it gradually crowds its body until all except the tip of the abdomen is protraded into the air, the elasticity of the straw causing it to hold the pupa m this situation secure from falling. Thus fixed the fly gradually emerges from the case. The Heßsian fly attacks the young corn plants m the autumn as well as m

the spring. In America, where it is necessary to sow the autumn wheat early

m consequence of the continuous frost, serious injury is often done. In this country (England) it may be hoped not so much harm will be effected m the autumn-sown crops, as immediately the frost comes the larvaj assume the flaxseed cases m which they pass the winter, and the crops, which without such timely aid would soon turn yellow and die, aro for a time safe." Writing of this unwelcome insect, the manner m which it has probably found its way to New Zealand and the possible results ot its advent, and of the mischief which it has wrong' t m other parts of the world, the Auckland " Herald " says : — " It is supposed to have been introduced by means of pupes adhering to straw used for packing goods imported from America. This is the way it is supposed to have been introduced to Britain, and, as importations of goods are made to the several Australian colonies, it would be interesting to know whether it ha=i reached there also. Its presence m New

Zenland, if it has not been detected m the Australian colonies, may act as a barrier to our surplus wheat 'finding a market there, and thus prove a disadvantage to this colony. Now that its presence m the colony is known, it should not be forgotten that it spreads and multiplies very rapidly. In Canada and the United States it is found over an area of probably not less than two millions of square miles of territory. In Russia its presence was first detected m 1879 by Pr K. Lindeman, Professor m the Academic Agricole of Moscow, and

m 188G it was estimated to have spread over a territory equal to about a million square miles. It will thus be seen that

it is an enemy to be vigorously dealt with if its attack i» to be kept within restricted limits. "Wheat, barley, and rye are the grains which are attacked by it, and last year barley crops m Invernessbire and Perthshire, Scotland, were found to be affected. From 1 770 to the present time the wheat and barley crops m the Eastern States of America have been occasionally severely injured ; but there is no authentic evidence of its existence m Europe until 1834, when it was discovered by Mr J. Dana at Mahon, Toulon, and Naples. Now it is found all 1 along the shores of the Mediterranean { Sea." Fortunately nature has, m part at least, supplied the antidote for the scourge m the shape of other ' insects which prey npon.tbe fly. It has, it is said, natural enemies m at least " five kinds of parasitic insects. The most destructive is one known as Platygastcr Error. This is a shiny black fourwinged fly smaller than the Hessian fly. It places its eggs within the eggs of the Hessian fly. The victims arrive at the pupal state, but no further, for the lavtp of the Blatygaster devour the" contents of the puparia, and wrapping themselves m cocoons, *ise them for their own purposes." We are glad to see it stated that the Government are endeavoring to introduce these parasitic enemies of the fly and it is to be hoped that they will succeed m the endeavor and that the parasites when introduced will thrive and multiply faster than the scourge they are to be imported to destroy, but meanwhile it will be well for farmers to lose no time m dealing with the 'pest themselves whenever it makes its appearance. -• TJuMkey may bogf <j 0 jy a<sng upou

the advice of Mr Charles Whitehead, of

*, tho Agricultural Department, m a report |on the subject which is quoted by the English paper above referred to he recommends that "m localities where there is a suspicion of fly, wheat should be put m late, m order that there may be no plants showing upon which the fly could deposit its eggs. Great care should be taken to extirpate all selfgrown wheat and barley plants round fields and near fields that have been • iufested during summer, and late developed plants of the first crop, as these will serve to Carry on the insect during the winter. When wheat and barley plants havo been infested with the fly, it would bo well not to sow wheat or barley m the ensuing autumn and spring near the affected Gelds . After au attack, and when the ' flax-seeds ' or chestnut-colored puparia are seen m the straw of wheat or barley plants, the straw should be cut high above tho second joint, m which, and m the second joint, these are invariably located. This may be done by setting the reaping machines high, or by putting men on to reap m very bad cases. Then the land should be immediately cultivated with a scarifier, or broadshare, and the stubble raked, or harrowed, together and burnt. Or the land may be deeply ploughed with close furrows, m order to bury every particle of stubble. All straw that has come from infested fields, and from those where there is any suspicion that the insect has been present should be closely I examined for 'flax-seeds.' If they wero 'found m large quantities a public- ■ spirited farmer would make a bonfire of the whole of the straw. The least that could be done would be to stack it as tightly and closely as possible, and to guard it jeaously that noue is sold, that it is all used m winter, and that all passes through the mixen. Cavings, short straw, and all refuse from the threshing machines should at once be burnt, especially if tho threshing takes place m the field. Before corn from infested fields is sown, and indeed m all cases before corn is used for seed, it should be examined for 'flax seeds.' If these are present the corn must be screened well ; but it would be safrr not to sow corn at all from infested fields, or m which a single flax-seed has been detected. Rough longstrawed manure that comes from London, or from other cities and towns, especially those near seaports, and of which immense quantities ara taken by farmers, even by those living at great distances from its source, is a most dangerous medium of infestation. All such longstrawed manure and litter must be submitted to the heat of the mixens, or at least the long straw within it. If m the late autumn, larvre or maggots are found fixed m tho stems of the wheat plants close to the ground a dressing of lime, or of soot, or guano, might be applied with advantage. If ' flax-seeds ' are found m the stems m the early spring, it would be well to feed the plants off closely witb. sheep if the soil and season are suitable. Heavy and frequent rollings with ' ring ' rollers would bo of great benefit when the state of the soil permitted. Dressings of stimulating manure put on infested wheat and barley plants m tho spring would force them along and strengthen them to resist the most dangerous summer attack of the second generation. Poor land gravelly spots, and ' stone brash ' or * stoneshatter ' soils, which are tho first to suffer, should especially be well dressed with manure. "Jhe crops on rich lands arc not nearly so much injured as those upon thin, poor soils." It is of course to be heartily hoped that the fly may not make its appearance m this Island at all, but we scarcely think that such immunity can reasonably be expected, and at least no harm can be done by forearming ourselves against the danger by making ourselves acquainted with the best methods of dealing with it, should it unfortunately require to be dealt with.