THE GRASS GRUB.

Manawatu Herald, Volume XXXV, Issue 1168, 6 November 1913, Page 4

THE GRASS GRUB.

BISULPHIDE OF CARBON FOR ERADICATION.

[By A. W. Green, in the Journal of Agriculture.]

The use of bisulphide of carbon has previously been advocated for killing grass-grub. It is, however, considered too expensive a remedy for general field practice. The high price of the material prohibits the treatment of large areas, but for ridding lawns or gardens of the grub there is no method so effective. Not infrequently is a lawn dug up and resowu on account of this pest having killed out the grass, and often the cause is erroneously put down to lack of moisture or absence of plant food. The grub is a silent but a consistent worker. Where it is prevalent, digging and immediate resowing is no remedy, for when the young grass comes up the grub is still there to feed on its tender roots. Thus the value of a soil-fumigant which kills the grub is made apparent.

It has been observed that the grubs prefer the roots of some grasses to those of others, and it may be possible to select from the numerous varieties offered by seedsmen a suitable lawn grass which would resist attack. To the writer the difficulty of securing such a grass appears to be increasing annually, for each season the number of plants added to the long list of those already attacked is considerable.

The common name “grass grub” may be somewhat misleading. They not only eat grass roots but are equally destructive on vegetables and the fibrous roots of trees, especially coniferous trees. They are most abundant in light sandy soil; they much prefer this to heavy clay. Kvem in small gardens they will be found restricted to patches of soil of the lightest and driest nature. Two plots of beet root growing in the nursery at Ruakura illustrate this: No. 1. sowu on light sandy soil, subsoil gravel, affected by grub ; No. 2. sown on heavier land, subsoil white pipeclay, unaffected by grub. A pathway 12ft wide divides the two plots. Both plots were sown on the same date.

It is during autumn that the grubs do most harm. They may then be fouud just under the surface of the soil, feeding on the fibrous roots of plants. In colour they are a dirty white, with darkbrown heads. Teuglh varies from -J-in to *in. Their harmfuluess can be noticed first about February, at which time they are of small size. It is at this time that treatment should be given, as it is not too late to save the plants, and the grubs are near the surface, The best method of applying bisulphide ol carbon is with the aid of an injection pump. The one in use at Ruakura is a ‘•Vermorel.” The injections can be regulated to any required depth by moving the tread. About '/ioz- is sufficient for each injection, and one should

bo made every 3ft. With this pump the time occupied to treat a lawn is ot little moment, aud the work is done without causing any injury to the turf. The cost of the material is therefore the main expeuse, but it is trifliug compared with the expense of breaking up the green. Without the pump it is necessary to make small holes about bin. deep, aud, after pouring iu the solution, to fill them up again, placing the turf iu its original position. It must be remembered that bisulphide of carbon is a dangerous preparation, and should be used oyly by careful hands. It is a transparent, colourless, inflammable liquid, emitting an extremely repulsive odour. It has great dispersive power. Its vapour is poisonous and very explosive when mixed with air; thus no light must be near when it is being used.