Manual and Chemical Control ofImperata cylindricaon Tea Land in Sri Lanka

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Abstract
In an experiment conducted in an almost pure stand of Imperata cylindrica to compare manual and chemical methods of control, forking out of rhizomes up to a depth of 45 cm gave long-lasting control. Slashing the grass to ground level at intervals of 4–6 weeks resulted in a low degree of control in terms of visual assessment of top growth and a high degree of control in terms of suppression of rhizome development, which was comparable to the most effective chemical methods; dalapon (22.2 kg a.i./ha) and dalapon–paraquat sequential spray. The results suggest that the effectiveness of control measures can be improved by timing the dalapon spray to coincide with adequate soil moisture reserve and by regulating frequency of slashing with regard to soil moisture status and the number of previous slashings imposed. The chemical treatment and the slashings suppressed development of rhizomes but did not cause increased rhizome mortality. The stage of growth at which dalapon was sprayed in dalapon–paraquat sequential spray treatment, did not influence the degree of control achieved as assessed visually.