BATTLING WITH THE TURNIP FLY.

Otago Witness, Issue 3018, 17 January 1912, Page 14

BATTLING WITH THE TURNIP FLY.

In some years as soon as the young plant becomes defined in the drills the turnip fly makes his appearance and attacks the plant, and although most of the turnips are thinned and seme of them are covering the ground there are others which are not sown yet on account of the unfavourable season, and may still suffer from the devouring energy of this minute and destructive beetle. Quite possibly the fly is always with us, but requires a'dryair and some degrees of warmth before it can multiply and appear in such myriads as to devastate the crops of whole districts. This year, so far.-has been too wet for its favourable development, but that it has only been biding its time and waiting for* a favourable opportunity is quite apparent. We were favoured last week by an enthusiastic farmer with some seeds of the poplar which he had secured from Middlemarch, into which the fly had bored a small hole at the apex and deposited its eggs in the hollow of the seed itself. Few farmers would anticipate that when they were improving their properties by planting shelter belts they were also securing a scourge for their own backs in the shape of -harbour for the turnip fly; but such the poplar has poved in Strath-Taieri. Everyone knows the activity of these nimble creatures, which start away at the approach of a footstep and make such a rattle that one is reminded of a miniature hailstorm ; but few farmers know how the winter and reappear in such numbers at the most undesirable time. The mature insect lives under clods, rough herbage, and stones in the fields and ditches during all the winter, and are invigorated by the warmth of the sun long before the turnip plants are ready to receive them ; but the fact that they also live in some forest trees should be published far and wide, so that these trees might be avoided when making fresh plantations. When they become active they attach themselves to any cruciferous" plant like charlock or any of the same order until the young leaves of the turnip appear, when they transfer their attention to them. It is just as well that farmers who allow such weeds to flourish on their properties should know that they do so at the expense of their own and their neighbours' winter feed. The fly has two active and two passive stages in its life history, which may be summarised into first the egg stage, then the grub, after that a resting stage, and finally the mature insect. The fly lays its egg on the under side of the leaf, and soon the little white grub is produced, which forthwith burrows right into the turnip leaf and feeds there for about a week. After being fully fed with the juicy material of the leaf the grub goes to rest for about a fortnight, and emerges from its sleep as a mature beetle. In this stage it feeds on the tender first leaf, and may destroy several brairds in succession. It is thus destructive in both of its active stages —as a grub and at maturity, Many ways have been tried with little success to pre'vent the attack of the fly, one of which is to sow plenty of seed—say 41b per acre —on the principle that some plants may get into the second leaf, and the fly can levy blackmail on the rest. Another is to cultivate the ground so thoroughly that cover is removed, and sow with the ceed some artificial manure in the drill, so that when the seed sprouts the tiny rootlets find .plenty of suitable food material, and rapidly grow into the rough leaf. And various other remedies, such as dusting them over with a mixture of lime, sulphur, and soot, or road dust alone, when the plants are wet with dew, have been tried; but there is nothing to beat spraying with paraffin (petroleum) along the line of plants just as the plants- come through the ground. The smell of the oil prevents the beetles from finding the crop, as they arc known to fly by scent against the wind, while oil on the leaf is distasteful if they begin an attack. The fly is known to breathe my means of minute holes situated along its sides; hence by clogging these up suffocation results. Hence we have the dust and sulphur baths, and thf-se have occasionally saved a crop, but they are not always available when wanted.