Browsing by Author "McKinlay, K.S."
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Item Cotton pest control in the Eastern Province, Tanganyika(1956) McKinlay, K.S.; Colonial Agricultural Insecticides Research Unit, Urambo, TanganyikaThis paper reports a series of experiments at IIonga Research Station, Eastern Province, Tanganyika, on the use of insecticides to control local cotton pests and on the interaction between time of planting, amount of insect damage and yield. The best yields were obtained by planting the cotton as soon as rainfall made it possible. Whilst loss of all flower buds for the first month of flowering made only a small difference to the yield, loss over a longer period would make the use of insecticides necessary and profitable. The choice of the best insecticide treatment is difficult; but of those tested the two best were either a mixture of lIb. D.D.T./t lb. Gamma B.H.e./ acre/application or Endrin at llb./acre/application, to be applied in 6-12 gal. of water per acre at weekly intervals during the period of insect attack. Time of planting and quality of cultivation have an overriding effect upon yield.Item Phytotoxicity of BHC to Cotton(1952) McKinlay, K.S. ; Namulonge Research Station, UgandaSince BHC sprays caused toxic symptoms on cotton in the course of field trials in Uganda, the effect of the compound was investigated on early-planted cotton in 1951. Sprays containing 0.065 and 0.025 per cent γ BHC, prepared from a 6.5 per cent dispersible powder or from a 3 per cent emulsion concentrate were applied when the plants were 4-12 weeks old at 30-150 gals, per acre, according to the size of the plants, and symptoms leading to leaf mosaic and plant stunting were observed a week later. Individual plants varied greatly in susceptibility, but there was no evidence of differences in phytotoxicity between the two formulations. The age of the plant did not affect its susceptibility, but only young green tissue was affected. Leaves more than one inch long at the time of spraying and those that developed after it showed no symptoms. A single application at the lower concentration had little effect, but repeated applications caused some mosaic. A single application at the higher concentration frequently caused mosaic, and stunting was common when the treatment was repeated at weekly intervals. The weight of green bolls was not reduced, even on the plots that had shown the most severe symptoms, and it was therefore concluded that BHC applied at normal rates should have no harmful effects on yield. This was confirmed later in the year, when sprays of 0.025 per cent γ BHC applied once a fortnight during most of the growing season caused no harmful effects and only slight visible symptoms. Laboratory experiments showed that root growth was much reduced when cotton seedlings were grown in a culture solution containing small amounts of γ BHC from the emulsion concentrate, but it was much less affected by the same amount of γ BHC (purified) from an acetone solution. In a discussion of these results, it is pointed out that the sprays might have affected the cotton through the action of the γ isomer as a growth-promoting substance [cf. R.A.E., A 40 81] or through the development of phytotoxic breakdown products of BHC [cf. 38 445]. Since preparations of the pure isomer only slightly affected the growth of the seedling roots, breakdown products were probably responsible.Item Use of Repellents to Simplify Insecticide Field Trials(Nature, 1956) McKinlay, K.S.; East African Agriculture and Forestry Research OrganizationA DIFFICULTY frequently met in insecticide field trials is that although the insecticide application may kill the insects on the treated plots at the time, these plots may be re-invaded very quickly by insects from the control plots and surrounding untreated areas. This is particularly marked in the case of trials on the control of cotton Lygus (Lygus vosseleri, Popp.), where the greater part of the damage is done by an immigration of highly mobile adults into the crop. One method of avoiding this difficulty is to use large plots of several acres in extent; but the very size of the plots seriously reduces the precision of an experimental comparison, besides being very expensive in time, materials and labour. Recent work has shown that where the principal purpose of the experiments is to study the effect of Lygus upon the yield of cotton, the result may be obtained very much more simply by using the repellent effect of certain insecticides.
