THE GRASS GRUB

Press, Volume LXXIX, Issue 23948, 15 May 1943, Page 3

THE GRASS GRUB

HUGE ECONOMIC LOSS. EXPERT RECOMMENDATIONS The grass grub problem forms the subject of a pamphlet issued by A. H. Flay and H. E. Garrett, of the staff of Lincoln College. In their summary the authors say that in Canterbury and North Otago ■ periodically many thousands of acres of pasture land are partially or wholly ruined. The worst damage is done on free silty-loam soils. On the Canterbury plains, because of the spasmodic nature of the attack and the irregularity of the infestation, a set cropping and stocking policy for any given farm is difficult of attainment.. The annual loss due to grass grub on an average 600 acre medium soil farm is £IBO, or 6s an acre. It is estimated that there are 2,000,000 acres of such soil in Canterbury, thus the annual loss here alone is over £500,000. The insect (Odontria zealandica), together with the caterpillar of the Porina moth, has been responsible for the destruction of thousands of acres of pasture and large areas of other crops, the writers continue. The Odontria lays its eggs mainly in November, while Porina is about one month earlier. The actions of the grub of the Odontria and the caterpillar of the Porina become obvious when they have attained one-half to three-quar-ters their size. This is from April onwards. The actual destruction proceeds throughout the autumn, winter, and early spring, when greatest injury to pastures and other crops is caused. At these times pastures are least able to withstand attack, owing to the dry conditions that often prevail in the autumn and to the lack of growth in winter and early spring. In conclusion, the writers say that the possibility of economic control on a farm scale appears remote, and recommendations meanwhile must be made along the lines of how to alter the farm management policy so as to result in the smallest financial loss. Recommendations (1) Extend the area in lucerne beyond that required for hay .purposes so that discriminate grazing of lucerne can be resorted to during pasture shortages due to droughts and/or grass grub. Cocksfoot is a grub resister, and if sown with lucerne provides < an excellent mixture for periodic grazing. One hay cut a year will appreciably lengthen the life of a periodicallygrazed lucerne stand. Although lucerne may be taken by grub in the first year of the life of the stand, established stands are seldom affected. (2) Build up and carry a greater reserve of dry feed, especially lucerne hay, so that when stock numbers must be reduced, such “surplus” stock are disposed of at "fats” and not as stores, In addition, permanent stock are maintained in good condition. (3) Fallow well and sow at least one paddock each year in Italian ryegrass and red clover or Italian ryegrass and green feed oats so that a supply of green feed is always available for winter and spring along with adequate dry feed. After'a lengthy fallow, at the worst only patches of this new pasture or green feed will be grub eaten. Under most medium and light land conditions it is advisable to sow an area of green feed oats each year. In seasons when grass grub attack is not severe it is advisable to give a paddock a good fallow and sow down to permanent pasture. Such new pasture sown on fallowed land provides a big bulk of green feed and might well replace Italian ryegrass in some seasons. (4) Always save grass and clover seeds. An area of ryegrass (Italian, perennial, or both) should be shut for seed, and red and white clover seed may be harvested in favourable seasons. Hold at least two years’ supply of such “home grown” seeds because, when grass grub attack is severe, seeds are always dear. (5) When forced to increase the area in cash crops, avoid early sowing of wheat or oats on land known to be severely infested with grub. If late winter or spring sowing is not wise on the particular class of soil or in the district, then sow wheat in paddocks not severely attacked and make spring sowings of peas, barley, rape, and turnips on badly affected areas. (6) Unless the whole paddock is ruined, do not be great a hurry to plough the affected area. Plough only for a specific and definite purpose. Where patches of paddocks are eaten out, often these will recover by feeding hay on them and then spelling. (7) Avoid loss of rape and turnip crops at the seedling stage, by sowing early or late —i.e., before the Odontria is on the wing and/or after it has laid its eggs. (8) As a general policy on mixed farms and in grass grub infested areas, be slightly understocked rather than a little overstocked. GRASS GRUB RAVAGES Reports from North Canterbury down into North Otago are to the effect that the grass grub is worse this autumn than for years. This is one result of the exceptionally dry season, which loaves a soil condition entirely favourable fc r the operations of the pest. The only immediate remedy, in the view of victims, is rain, which will bring the grubs to the surface, where the frosts and the birds will take their toll. The birds are dependable to do a certain degree of destruction, but the frosts arc rather a broken reed to depend on. An instance of this being tested was related to the writer the other day. In the test a number of the grubs were placed in the freezing chamber at one of the meat works. They came to life in the open air quite unaffected at the end of a fortnight. “Straggler” saw a year or more ago in Marlborough a field which was badly affected with the grub. Alongside was similar land, with similar working, grass, and treatment, and it was practically free of trouble. The owner explained that the difference was entirely due to the liberal dressing of superphosphate that the healthy paddock had received. That remedy, of course, is out of the question at the present time, even if it were accepted as an undisputed test, but it is worth while reflecting on the extent to which the prevalence of the grub may have been assisted this last two years by the fertiliser starvation of the soil. The grub, with its kindred pest—the caterpillar of the porina moth—have been widespread in their depredations this last two months. Lincoln College is applying a mixture for the porina caterpillar successfully used last year— Paris green, bran, and molasses. In another column appears a condensation of a pamphlet on the subject prepared by Messrs A. H. Flay and H. E. Garrett, of the staff of Lincoln College, in which the losses created by the pest are pointed out and steps to minimise it recommended. The immunity of lucerne from the incidence of grass grub, except in the case of very young stands, is noted in the pamphlet. Another crop that shows a remarkable recovery from the pest is subterranean clover. Paddocks apparently eaten bare and grubbed or skim ploughed have come back better than ever. The pamphlet suggests that the annual loss to Canterbury producers through the pest is more than £500,000. the area of soil liable to infestation being 2.000:000 acres. These figures are fierce enough to cause deep thinking. ’The proposed new Ayrshire Association for England and Wales has a problem ready made for it; to what extent will it be in favour of dehorned animals? Of all the cattle breeds the Ayrshire might be said to be the most horn-conscious. Horn training by various gadgets of weights and pulleys is not unknown and there may be a conflict of interests and opinions which will take some judicious handling. The delicate line of an Ayrshire’s horns is one of the things that gives it such a handsome appearance. But, says an English paper, the times are .stern and problems of this kind will have to be faced.