Transactions of RHASS Volume 1940 - Page 034
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| Year | 1940 |
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| OCR Text |
56 THE CONTROL OF PESTS OF FARM AND GARDEN CROPS. Preparation of Dusts :— Nicotine Dust—Mix together 7 1b. nicotine sulphate, 93 lb. bentonite, and 1'6 oz. organic soap. Dorris Dust—Mix together 19 1b. derris powder, 81 1b. talc, and 1-6 oz. organic soap. Sulphur Dust—Mix together 60 1b. Sulphur, 40 1b. bentonite, and 1'6 oz. organic soap. Davis-Sulphur Dust—Mix together 19 1b. derris, 25 lb. dusting sulphur, 56 1b. talc, and 1'6 oz. organic soap. The ingredients should be weighed out and transferred to an old end-over-end barrel churn of a convenient size. Then add about 32- lb. rounded stones from 1 to 2 inches in diameter for each 1b. of powder to be mixed. The churn should then be rotated until the ingredients are thoroughly mixed, after which the powder should be separated from the stones. Dusts are generally applied at the rate of 25 to 30 lb. per acre With the aid of a dusting machine, which blows the dust among the plants to be treated. MERCURY DUSTS. The mercury dusts have ahnost entirely replaced corrosive sublimate solution for seed dressing, and the treatment of certain insect pests which attack the roots of plants. Seed treatment with dusts, such as Ceresan, Agrosan G, and Segralin, is much preferable to any form of wet treatment, because it eliminates the very troublesome after-treatment of drying the seed. Dusts for seed treatment generally consist of 2 per cent of an organic mercurial compound, such as ethyl mercury chloride or phenyl mercury chloride, and 98 per cent of an inert carrier. They are used at the rate of 1 to 2 ounces of dust to 1 bushel of seed, but experiments at Oraibstone, the experimental farm of the North of Scotland College of Agri- culture, have shown that the amount of dust required depends upon the time of treatment. Seed treated in December only required 1 ounce of dust per bushel, while seed dressed im- mediately before sowing in spring required 2 ounces per bushel. Great care must be exercised in dressing seed with one of these dusts, because of the extremely poisonous nature of mercury compounds. The seed should be treated in a closed container or a special seed-dressing machine, and the operator should be protected against inhalation of the dust. Treated seed, which is not required for sowing, should not be fed to animals or poultry unless it is thoroughly washed with water to remove the last traces of the mercury dust. It must always TJIE CONTROL OF PESTS 0F FARM AND GARDEN CROPS. 57 be borne in mind that mercurial poisoning is one of the most difficult forms of poisoning to treat. Some of the most serious pests which market growers have to contend with are the Cabbage Root Fly and the Onion Fly. The damage by these pests is caused by the larval or maggot stage of the flies feeding upon the roots of the plant below ground level. This mode of attack makes it very difficult to control the pest, but recent experiments with calomel dust have been very successful. The dust, which consists of 4 per cent calomel and 96 per cent inert carrier, kills the eggs of the pest when laid upon treated soil. The dust is applied to the soil round the base of the plant, and, since attack may occur throughout the growing season, it should not be disturbed by close cultivation or weeding. Brassica plants should be given two dressings, the first within four days of tranSplanting and the second two or three weeks later at the rate of about 1‘5 ounce per plant. Onions should also be given two dressings, the first when the seedlings appear above the ground and the second about ten to fourteen days later, each at the rate of about 1% ounces per square yard. COMPATIBILITY AND INCOMPATBILITY OF INSECTICIDES AND FUNGICIDEs. The following table indicates the commonly used substances which may be safely mixed in the preparation of sprays and the combinations which should be avoided :— TABLE. |
| Title | Transactions of RHASS Volume 1940 - Page 034 |
