Use Of Selective Herbicides Research Articles

Establishment of Birdsfoot Trefoil as Influenced by Competition from Weeds and Companion Crops1

SynopsisSeeding without a companion crop, reducing competition from companion crop by grazing and the use of selective herbicides are means of increasing chances of successful establishment of birdsfoot trefoil. Pre‐emergence applications of TCA or post‐emergence dalapon have controlled grassy weeds and enhanced survival and vigor of trefoil seedlings. A combination of dalapon and 4(2,4‐DB) has shown promise of controlling grasses and many broadleaf weeds without serious injury to the trefoil.

The control of malaria in Borneo (An account of the Tambunan experiment)

1. (1) In previous work, Anopheles maculatus was exonerated, and “ Anopheles leucosphyrus” was incriminated as the chief vector of malaria in Borneo (as it would appear to be throughout a considerable part of the East). 2. (2) Based on this work, the Tambunan Experiment was carried out in North Borneo from 1949 to 1952, to determine whether the admission of sunlight to seepages, followed if possible by cultivation to render it permanent, eradicated not only the vector but the malaria which it carries. 3. (3) An area of about 10 square miles of particularly difficult jungle-covered hills was selected, in which spleen rates had been maintained at over 80 per cent. for at least 14 years. In this area, jungle was cleared over all seepages, numbering about 200, and involving about 32 miles of waterway. 4. (4) There was an immediate 95 per cent. reduction of vector breeding. This was maintained throughout the 3 years without significant further work. 5. (5) There was a fall in spleen rates during the 1st year, from 86 per cent. to 56 per cent. This fall was continued during the subsequent years to 53 and 45 per cent respectively. 6. (6) There was some malaria transmission remaining, as shown by parasites in the blood of some young babies.This was possibly due to infiltration of infected mosquitoes from surrounding uncontrolled highly malarious villages. 7. (7) In a Comparison Area, the spleen rate, maintained at 100 per cent. at every examination during the previous 14 years, was still 100 per cent. during the first 2 years of the experiment while conditions remained the same. 8. (8) During the final 2 years of the Experiment this spleen rate fell unexpectedly, and for the first time on record children were found without evidence of malaria. This was found to be due almost certainly to the enthusiasm of a new Village Headman who had distributed drugs to the children, and had imitated the methods carried out in the Experimental Area. 9. (9) It is considered very desirable that measures should be undertaken over a larger area, on the scale of an actual campaign, to eliminate infiltration of infected mosquitoes, to test other means of clearing such as the use of selective herbicides, and as the next justifiable step in the conquest of malaria in those lands where “ A. leucosphyrus” is the vector. 10. (10) It is believed that the Tambunan Experiment has shown this method of malaria control to be effective, relatively permanent, and able to be applied by the people themselves, to the advantage of their agriculture and to the economic development of the land.

Weed Control by Chemicals Trails with Extra "A" (Sandoz)

Control of weeds in cultivated crops by the use of selective herbicides has become increasingly popular. A good measure of success in this direction has been reported by workers in India and elsewhere.. The active chemical ingredients of the many commercial formulations in the market mainly consist of 10% of sodium -4 chloro-2 inethyl phenoxyacetate, 80% of the sodium salt of 2-4-D, 40% of the butyl ester of 24-D, sodium and ammonium trichloracetates and dinitro-ortho- cresol. Sumai (Panicum miliar, Lam) is an important goodgrain erop raised on the Nilgiri hills in rotation with potato and forms the staple diet. Being a slow-growing millet it is overpowered very quickly by spurry (Spergula arvensis), a pernicious weed of the region. Very often the entire crop succumbs to this and other common local weeds like Oxalis and Polygonums Handweeding is not always possible, due to scarcity and high cost of labour.

SELECTIVITY OF HERBICIDES

With the introduction of new organic chemicals, the use of selective herbicides is finding broader application. Stimulated by war conditions, their use offers a promising method for increasing efficiency and reducing drudgery of agricultural production. Early work on selective herbicides is reviewed by ?slander (1), and by Bobbins, Crafts, and Raynor (17). This paper considers selectivity from a broader viewpoint, discussing the selective killing of annual weeds in crops of the family Umbelliferae by oils, the control of annuals and shallow-rooted perennials among deep-rooted perennial crops, and the selective use of growth regulators as sprays and soil amendments. Plants differ in many ways ; their surfaces vary in form and chemical composition ; some are easily wet by aqueous sprays ; others are difficult to wet. Surface coatings vary in permeability, and protoplasm responds specifically to different chemicals. The gross structure of plants varies in such a way that the meristematic tissues of some are exposed and vulnerable to sprays, others have their growing points protected. Because of these differences certain weeds may be destroyed in growing crops with little or no injury to the latter. The nature of selectivity