THE MEALY BUG.

New Zealand Herald, Volume LXVIII, Issue 20868, 9 May 1931, Page 8 (Supplement)

THE MEALY BUG.

METHOD, OF CONTROL. A correspondent—"R.C.V.P., Hamilton — writes in regard to tho mealy hug. Fumigating with hydrocyanic gas is, without doubt, one of tho most offectivo means of controlling this dire pest of the grape flower. Although it entails a certain amount of labour and expense in preparing the vessels and manipulating the materials required, it is money well spent if by its use good, clean fruit can be obtained. Being a deadly gas, it requires special car'e in its application.

The 'safest and most effective method is to arrange small wood boxes, with a sliding bottom, zinc being the best for the slide. These should be arranged the whole length of tho house, and bo placed in a straight lino and about 9in. from tho ground, forming tho line of boxes about 3ft. out from the stem of the vines. If the house has a span roof they should be arranged on both sides. The slides on the boxes should all be connected with one wire, or, if the house is too long, two wires, reaching to the outside uf the house, at each end. ( ARRANGEMENT OF BOXES. In arranging the boxes one should be provided for about every 200 cubic feet of space, as the object is to have the gas as ovenly distributed as possible. This gas is very quick in its action, and rises almost immediately over where it is generated. It is in tho boxes with the sliding bottoms that the cyanide of potassium is placed, while, for placing immediately under the boxes, some earthen vessels —soup plates are useful for tho purpose—should be provided in which to place the sulphuric acid. For about every 200 cubic feet of 6paco 2oz. of sulphuric acid in 6oz. of water (liquid measure) should be placed. Immediately above in the boxes should bo placed of cyanide of potassium. In arranging the material in the vessels, first, place tho sulphuric acid and water in the soup plates. Then, after seeing that the slides in tho boxes are all in order, put in tho cyanide of potassium. Close up the house, and lock it if necessary. Then pull the wire from tho outside, when tlie whole of tho contents of tho boxes will drop at once into the vessel below and generate the gas. Some growers adopt a more simple and cheaper method—that of wrapping the cyanide of potassium in paper and hurrying through the house and dropping the paper in tho vessel containing the sulphuric acid. Owing to the deadly nature of the gas, however, Ihe risk of this method is far too great for any but those that are thoroughly used to it.

ACTION OF THE GAS. If the fumigating appliances are properly arranged, they will last for years, and as the house may require fumigating two or three times during tho growing and fruiting season, as well as in autumn or winter, the results obtained will more than compensate for the labour and costs incurred. The cyanide gas not only destroys bug, but also thrips, leaf rollers and other pests that attack the vines and foliage. Fumigation tan bo performed any time during the summer after the foliage and wood is fairly well matured, but it is always advisable before fumigating to remove any soft, sappy growths, to avoid them being scorched. A dull day, or at evening, is the best time to perform the operation.