THE GRUB PEST.

Otago Witness, Issue 1731, 24 January 1885, Page 7

THE GRUB PEST.

_.. A number of correspondents have written L the last few weeks inquiring as to any Vnethods for preventing the ravages of grub on pasture and on the roots of crops generally* It appears the plague is 1 this season very troublesome, particularly in the Sonthem districts, and is proving very destuctive. Unfortunately these pests are very difficult to get rid of, requiring the attention and labour of not one year, but two or three, as will be evident from our description of the habits of the insect. One correspondent has sent a specimen of tho larva, which is that of the Melolantluz vulgariq, commonly known as the brown beetle, chafer, May bug, &c. Some years it appears in prodigious numbers in particular localities, as in the cage now under notice, and commits both in its larval and perfect state the most serious ravages ; in fact it is- tha most destructive insect we ha^ve in our midst. The female beetle deposits Ecy eggs in the ground, where in a short time they chaage into young grubs; these, when full grown, attain a size of from ftn inch to an inch and a half in length ; soft, thick, and fleshy ; white and yollowish, with a reddish head and stroug jaws. The period the insect continues in the- grub state is generally considered to be four years ; in fac!^ close watching and careful practical trials have proved this. During this long period it commits dreadful ravages on the roots of grasses, plants, and even trees, gnawing away the fibre and bark, and devouring the roots, bo that in pasture land the, turf becomes brown, and may be rolled up with nearly as much ease as if it had been cut artificially. On removing it the grubs will bo found lying on their sides, rolled up within tbe mould, when they can be gatheted in great numbers and destroyed. When full grown these larvae dig into the ground to a depth of two or three feet, and even more, spin around themselves a smooth case, and then change into the chysalis state. In thia inactive state they remain until tho following spring; the perfect beetle then comes from the ground and begins its attack on tbe leaves and blossoms of fruit-trees, and does not

disdain toattack theleaf of almost any tree in Ihe bush, whether native or imported. T^ie beetle la not long buzzing round until the female begins depositing her eggs, 'and so theplagpe goes on constantly increasing. . Were it not that the following statement is authentic, and rworded in vol. xix Philosophical Transactions, it would hardly be credible. In 1688 the cockchafers appeared on tho hedges and trees in County Galway in clusters of thousands, clinging to each others' backs in the manner of bees when swarming. During tho day they remained quiet, but towards sunset the whole were in motion, and the humming noise of their wings sounded like dietant drums. They were in such prodigious num bera as to darken tho air over a space of nearly three miles, and the noise made in devouring the leaves was compared to the sawing of timber. Over a large space of the country every blade wae destroyed, so that in midsummer the trees were as bare as in midwinter. Swine and

poultry devovfred them in vaat ; numbers, waiting under the trees for a cluster to fall, ( devouring them greedily, and becoming fat on the dainty morsels. Even the lower orders of the people, from the scarcity of other food, adopted a method of cooking the beetles and BubsisfcKl on tbem for' a time. Towards the end of the summer tho beetle suddenly disappeared. It will be evident, then, from the habits of the insect, its great numbers, and its power of flying from one place to another, that the labour of getting rid of it is' no easy task, nor can it be accomplished in a short space of time, or the pest be ever completely eradicated. We come now to consider tbe various suggestions made for the prevention or cure of the mischief caused hy the pest ; and these will be enumerated as clearly and explicitly as possible. Taking the insect first in its winged state as a beetle, there is no question that insectivorous birds and fowla are a great aid in keeping it in check. TJhoUßands of them are picked up by atarlinga, blackbirds, &c, as they emerge from tne ground in the last chrysalis stage, much like the perfect boetle in, shape but without the power of moving about. It lies with tbs forming limbs and mouth parts beneaijh^.Msually all cased in separate sheaths, •i»4fl n outer skin, unfSl it is matured, when it gams strength to free its limbs, and takes to flight in its full colour and powerß. In this condition it is easily captured and destroyed, and onr great assistants are birds, fowls, and pigs, all of whioh devour the inseot in all its stages very greedily. Even when in its full vigour m»y of tbe perfect beetles lie on the ground during the day, especially females depositing their eggs. Others lodge in the trees under the shade of the leaves, and by a sharp shake can be thrown down, when their enemies speedily pick tjaem up. Again, during the evening the plan bf netting is adopted, which is suited for a small garden orshrubbery but not for extensive practice. Another and more effective plan for their destruction is the kmdlmgof fires as night closes in; the light ijttractq the beetles and other injurious moths, which, Sying into the flame, are soon conflumed or disabled. There are no other methods «?S J no * Ied |fe °* /eßtooyinc the beetles except it- be the introduction 0! bats and vQSLQBf In the grub state they are not more easily got at. But aa a prevention all decaying leaves or vegetable matter in which the egg or 3 may be sheltered should be gathered Vhlaps ■Udbjroed;, u Tpp ; dresßnigwith fresh lime or pa w&fca fab ftfeW*ta»f to destroying wm

bars of the young larvae, but after they are a yeur or two old and have attained a fair size neither of these have much effect. Wo have often tried the experiment of digging up a good strong lump of a fellow and giving him a good coating of hot lime, but its only effect was to render the creature more active and agile, as he moved about pretty smartly, rubbing himself against whatever came in his way to get the dust rubbed off bis C3at and thou burrowing into the ground. Some of these we have kept ia bottles filled with earth for days, giving them a dally dose of lime, but with lifctle effect. A certain death to them, however, is gas or ammonia water ; a drenching of this the strongest of them will not survive. It ha 3 these objections, howev&r, that applied in its full strength, bo as to be thoroughly effective on the insect, it also destroys the plant, and further, if the grub is any distance down the liquid does not reach it. In using gas water frequent application in a diluted state is the best plan ; but, unfortunately, here the strength of the liquid, aa supplied from the gas works, varies so much that uo rule can be given as to the quantity of water to add. Ono effective remedy, which nature occasionally provides when fcbe lay of the land is suitable, is flooding. The grub cannot exist without air, and when an infested field ia flooded for twenty-four hourß or more the doad grubs will be found by the thousand on tho surface, having come up to breathe. The different aids which have bsen discovered for lessening this evil have been thus far enumerated, consisting of birds, fowls, and animals, fire, water, and chemical application ; to aid these much depends on labour in turniug up or stirring the soil, which is the great seftret of success. The birds and the pigs, too, seem to have an instinctive knowledge of where the grub lies buried ; these are comparatively powerless to dig thorn up, however, and tho spade or plough must be brought to assist them. When pasture fields are infested in patches the application of top-dressing, after burning off tbe destroyed plants, should be liberally reported to, and this ef tho strongest character ; and thereafter the piece of ground should be well turned over, giving a fresh application each time, and by this moans huccesßwould be certain. It must, however, be borno in mind that tha utter and entire eradication of tho peat is nol; to be anticipated, as after one horde has been destroyed a fresh colony may aoon take its place.

The smaller specimens are the larva aud beetle {Odontria striata), less in size, but not less numerous and destructive th«n the larger chafer, and requiring as strong measures to keep down. In habit they are very much alike — perhaps in the larval state the smaller one is oftener found in patches and hardly so deep in the ground. It is, however, certain that tho destructive beetles and moths with which we have to contend, committing their depredations both by day and by night, form an exceedingly groat acmy, presenting numerous points of attack, oil of which must be takcm advantage of if they are to be kept in subjection.