THE GRASS GRUB

Evening Post, Volume CXV, Issue 10, 13 January 1933, Page 14

THE GRASS GRUB

EXTENSIVE RAVAGES

COMBATING THE PEST

Owners of lawns, caretakers of bowling greens, orchardists, and farmers in general, are all intimately concerned with tho grass grub, the depredations of which during tho various stages of its life history cause considerable loss annually in practically all parts of the Dominion. Tho ravages of the grass grub seem to be getting worse each year, arid the problem of its control is one which is exercising the attention of the Dominion's entomologists. In a recent lecture to farmers of the Nelson district, Dr. D. Miller, of the Cawthron Institute, gave an interesting account of the life and behaviour of the grass grub, which, he said, was the larva of a cockchafer beetle miscalled the "turnip fly" by farmers. The beetle swarms at dusk, during mild evenings throughout November and most of December, and at that time does very extensive damage by defoliating various forms of vegetation ranging from trees to herbaceous plants; The farmer is mainly interested in tho beetle owing to its depredations upon crops of seeding'turnips and rape: extensive areas of these are sometimes destroyed in a night, since it is chiefly during the period of flight that such crops are at a stage most susceptible to attack. ■This■■necessitates -a resowiug -of the crop one-or more times before a satisfactory strike is secured. This is.due to the fact that in the seed-leaf stage turnips and. rape are dependent upon two small leaves which make an excellent meal for the, beetles; when the plants are in full leaf the . beetle would not seriously injure them. In some localities where turnip and rape crops are sown during October they are sufficiently advanced .by November when, .the beetles are on?the wing to withstand . the invasion; but ■ where sowing takes place during November the young plants have but little opportunity to eseap'e destruction. Therefore, during seasons wnen'the beetles are abnormally abundant, arid whoii the first sowing is destroyed, it is a waste of time to respw until the" first week in., December, -since Ijy tho time germination has taken place and the seed-leaves show above the ground the majority of the beetles have ceased to fly. For tho purpose :pf couponing, the beetles, .attempts are;, sometimes made to destroy them by lighting bonfires at night, to which the insects arc attracted; this method may bo. of use to a limited extent, but is not an effective method :of . control. : A very ingenious method, -'and one that should be worthy of trial by.tho farmer for the protection of his.young crops, was devised a few years ago by. Mr. D. J. Buchanan, of the State Forest Service. At that time the young trco rtoolc in the nurseries ,at Tapanui was seriously damaged by the attacks of-grass grubs on the roots. These grubs were the progeny of beetles that infested the nursery bods iwith their eggs, fully. 500,000 plants being; lost in ono season followed by the loss of the; entire- crops of 1,500,000 seedlings in the following year. In view ; of this serious position Mr. Buchanan devised a system of fumigation. Ho spread sulphur ou strips of old scrim which ;wero then rolled up and placed.in disused paint pots; these pots were set here and there among tho trees in the nursery, and fired at dusk during the period of. beetle flight, except when the weather was unsettled, since tho beetles are not active at such times. In the mornings he found numbers of dead beetles on the ground. The following year in a crop of about 3,500,000 seedlings not a single plant was destroyed, nor were grubs found in the ground..'lt would seem, therefore; that' Mr. Buchanan's process should be effective' in keeping, the beetles from attacking young crops and at thp same time prevent them from laying their eggs in the ground; for this latter purpose also the fumigation would be advantageous for protecting pasture during periods of abnormal beetle activity. ,; . : . THE ROLLER AND BIRDS. The, .grass grub is active upon, the roots of.pasture and:other plants from December to about the end of -: September, after which most of: them cease feeding to undergo their transformation to i;he beetle stage. The grubs are very difficult -to control though; certain practices are worthy bf note. During feeding: the grubs not only devour roots but .also swallow quantities of soil;,in the'case of. heav-ily-infested, pasture this results in the surface soil becoming pulverised. Wherever practicable,.4herefore, rolling such infested areas, recompacts the soil and re-establishes the normal circulation of soil moisture about; the grass roots, and has a-decidedly beneficial influence upon the pasture. On the dairy farm where severe grub : infestation may occur in patches, it has b.een found advantageous to-attract cattle to such places by means of some palatable fodder; the hooves of the. animals by sinking into the,pulverised soil tend to crush.the larvae and so lessen their influence upon the pasture. The beneficial influence of birds, (especially starlings and. even sparrows) is not to be overlooked. Birds will extract the grass grubs from the ground, when the latter are feeding close to. the surface, and will' readily follow the plough devouring the' grubs as they rbecome exposed. It is also to be noted that certain types of pasture plants are more resistant to grub attack than others. , On this.point, Mr. A. H. Cockayne,, of. the.Department of Agriculture,, states, that., such types are clovers;1 especially red clover, cocksfoot, crested dogstail, and Danthonia pilosa; while perennial ryegrass readily succumbs, to the. influence,of the grub. The grass grub in New Zealand is remarkably free from the influence of parasites, but researches are being,now carried out upon, a.Chilean parasite at the. Cawthron Institute, and other likely parasites are to be studied in conjunction with this species. .-.';"