THE GRASS GRUB

New Zealand Herald, Volume LXIX, Issue 21281, 7 September 1932, Page 16

THE GRASS GRUB

MEASURES FOR CONTROL NEED FOR INFORMATION " I agree with the remit, carried at the New Zealand Co-operative Dairy Company committeemen's conference, that the Department of Agriculture be urged to concentrate on combating the grass grub," writes Mr. F. W. Walker, of Otorohanga. " But, so that there will be no time lost in carrying out tests before the grubs change to beetles and make their flight in November, wo need to learn more about their habits. " In the South Waikato and North King Country tliero are two kinds of grass grub, whose habits are similar. I will distinguish between the two by calling them No. 1 and No. 2, In the Upper Thames Valley I have had experience only with the No. 1 grub. It is of a greenish-brown colour and emerges from the ground as a beetle in November or early December. These beetles immediately settle in millions on the tea-tree, where they feed and fertilise, the leaves of which are their favourite food.

" In about two weeks they are ready to lay their eggs, poor loamy soil being preferred to rich, damp or heavy land. Often they are laid in hay paddocks which are not cut until after Christmas, but never to my knowledge have eggs been laid in the same paddock twice in succession. As soon as the grub is hatched it feeds on the rootlets of the finer grasses and clovers. If the paddock is in good heart, and there is an average rainfall, little damage is done, as the rootlets grow just as fast as they are eaten. Pasture that has not been top-dressed and not sufficiently grazed is likely to suffer heavy damage, so that the best safeguard is to keep all paddocks grazed or cut short while the beetles are on the wing. Heavy rains cause the grubs to come close to the surface to breathe, when birds, especially starlings, take a big toll. During a dry season, similar to the last, the grubs work all the soil from two and a-half inches deep to a fine tilth. Owing to the dryness, they are not forced to come up to breathe, which means that the birds are unable to do their work of exterminating them. Dryness means also that the rootlets eaten by the grubs have no further growth. " The No. 2 grub will be much more difficult to deal with, as it attacks the same paddocks year after year. It is larger than the No. 1 beetle, is brown in colour, and in thi3 Lower Waikato Upper King Country district hatches in November and December. It flies in the evening and night, doing extensive damage, and disappears into the ground, under the trees it has been feeding on, I during the day. This beetle lays its eggs in bare paddocks, and, according to tha description of what they feed on and the length of time they remain in one paddock (several years), I think this is the grub that is doing such damage at Manawaru. Low-lying grass paddocks, even if dry, are not touched here, so evidently they prefer the lighter, rolling land." Mr. Walker quotes individual instances in which top-dressing and rainfall have apparently had a restrictive influence on the depredations of the grub and suggests that if farmers in affected districts would combine with the Department of Agriculture in carrying out tests with various manures and quantities per acre, and also with sprays for trees, before the grubs leave the ground, they would be, able to tell, when the new crop of grubs are hatched in February, what manures or combination of manures and the quantities per acre they dislike. There is one shrub, named Andromeda japonica, he says, which the grubs eat with fatal results, for they can be seen Iving two inches deep dead beneath this particular shrub. This tree, he suggests, should be well "worth trying out, especially around orchards.