Transactions of RHASS Volume 1940 - Page 029
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| Year | 1940 |
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46 THE CONTROL OF PESTS OF FARM AND GARDEN CROPS. to be safe with most plants. Recently there has become available a very pure grade of kerosene named ‘Odourless Distillate,’ which is ideal for a summer spray. This oil has a purity of over 99 per cent, and, although it is more expensive than ordinary kerosene, it is cheap enough for wide use as an insecticide. The makers give the following specification for this oil: specific gravity, 0-778; viscosity, 36, Redwood No. 1, at 100° F. ; distilling range, 370° F. to 500° F. ; un- sulphonated residue at least 99 per cent, and leaves no unpleasant residue behind. The oil is used as an emulsion at a concentration of 2 per cent, except for very tender plants, when the concentration is from 1 to 1:}.— per cent. This oil may be made miscible with water by dissolving in it creSylic acid soap as described under mineral oil winter wash. This miscible oil spray should not be used in conjunction with, or immediately before or after, lead arsenate sprays, since cresylic acid reacts with lead arsenate and liberates water-soluble arsenic. A quick—breaking emulsion may be prepared as follows: place in a barrel or other container 2 gallons of water and add 2 fluid ounces of 28 per cent ammonia solution—ordinary household ammonia is about this strength. Add slowly, stirring all the time, 3 ounces of casein, stir for about 2 minutes, and then add 5 gallons of the oil, stirring briskly for several minutes. For a 2 per cent emulsion dilute 1 part of this mixture with 35 parts of water. N Martina—Nicotine, while classified as a contact insecticide, is also a valuable stomach poison and also a fumigant. It is not injurious to foliage in any concentration. There are two forms of nicotine on the market—one a commercially pure form of the alkaloid itself containing 95 to 98 per cent nicotine, and the other a water solution of nicotine sulphate containing 40 per cent of nicotine. The nicotine sulphate solution is comparatively stable if protected from evaporation of the water. Pure nicotine must be tightly sealed or loss will occur by volatilisation. Nicotine sulphate is generally employed at the rate of 1 pint to 100 gallons of water, and the pure nicotine at 8 to 10 fluid ounces per 100 gallons of water. All nicotine solutions should have a Spreader added to them for spraying, such as sodium lauryl sulphate or one of the proprietary spreaders. Generally 4 to 8 ounces of the spreader per 100 gallons of water will be sufficient. It is advisable to add 1 or 2 lb. of slaked lime to each 100 gallons of nicotine Sulphate Spray to increase the volatility of the nicotine. Nicotine may be combined with lead arsenate, Bordeaux mixture, and lime sulphur sprays to form general purpoSe sprays. Dm‘ris.——Derris powder consists of' the ground roots of THE CONTROL OF PESTS OF FARM AND GARDEN CROPS. 47 certain tropical plants belonging to the family Leguminosw. Representatives of the genus Derris are found throughout the trepics, especially in the Malay States and South America. Powders obtained from diflerent Species are sold under the names of Derris, Cube, Timbo, and Barbasco. The principal toxic substance in all these plants is a complex chemical compound named Rotenone, having the formula 02311220. Formerly the rotenone content of different powders varied greatly, but now methods of analyses have been evolved which enabledifferent samples to be graded and standardised. ,\ good quahty of derris powder should contain from 4 to 0 per cent rotenone. In buying derris powder a standardised powder of known rotenone content should always be purchased in preference to powders of unknown quality. The great value of derris hes in the fact that although it is very poisonous to insects and other cold-blooded animals it is harmless to warm-blooded animals. Derris powder of 5 per cent rotenone content is generally used at the rate of 1 1b. of powder to .30 to. 100 gallons of water. A derris spray should always contain a wetter such as soft soap or a proprietary wetting compound. Soya bean flour has also been added to derris sprays to act both as a wetter and a sticker. A good derris spray is made up as follows: derris, 1 lb. - soap, 2 lb. ; water, 50 gallons. Derris powder may be mixed With sulphur, but should not be used with lime sulphur or Bordeaux mixture. . Pyrethrum.——Pyrethrum is one of our most valuable contact insectmides. The use of pyrethrum flowers for insecticidal purposes appears to have originated in Persia. The Persian insect powder was made from Pyrethrum roseum and l'. carncum, and was introduced into Europe early in the nineteenth century. In the middle of last century a new species, P. cmerm'iwfolium, was produced in Dalmatia and quickly superseded the Persian species. Although there are abouta dozen members of the genus Pyrethrum which possess insecticidal properties, only P. cinerarimfolium is of com- niei‘CIal importance in Britain. Up to the outbreak of war in 1911- Serbia was the largest producer of pyrethrum flowers The war cut down this production and enabled Japan to seize the market, and she still remains the largest producer During the last few years the cultivation of pyrethrum has been undertaken in other countries, and the highest grade {lowers are now produced in Kenya. The active principles of pyrethrum are two complex chemical compounds termed Pyrethrin 1 and Pyrethrin 2. These substances belong to the chemical group known as esters and like all members of this group, are easily broken down b, compounds containing strong alkalies, such as soap and washing soda. Pyrethrum sprays, therefore, should never be |
| Title | Transactions of RHASS Volume 1940 - Page 029 |
