Control of white root disease in immature rubber with three systematic fungicides
1991
Chan, W.H. (Applied Agricultural Research Sdn. Bhd., Sg. Buloh, Selangor (Malaysia)) | Wong, C.P. | Wong, C.C.
Three series of experiments were laid down on 18 month to 30 month old PB260 to evaluate the effectiveness of Bayfidan (triadimenol), Bayleton (triadimefon) and Tilt (propiconazole) against the disease. The results indicated that treatment success depended on severity of infection at time of fungicide application, rate and type of fungicides applied and method and frequency of disease inspection. The degree of infection at the collar appeared critical to treatment success. When disease infection advanced beyond the severe stage with concomitant yellowish foliage symptoms, all three fungicides were ineffective against the disease. Conversely, when infection had not crossed the severe stage, trees could be 'saved' by application of Tilt at 7.5 ml, Bayleton at 15-20 g and Bayfidan at 20 ml when infection was severe and 10 g Bayleton, 10 ml Bayfidan and Tilt also at 7 and half ml when infection was slight to moderate. Collar inspection resulted in much higher treatment success than foliar inspection as infected trees could be detected at a much earlier stage. Most diseased trees detected by foliar inspection were beyond 'saving' as infection had advanced beyond the severe stage. Reinfection of disease appeared about six to ten months after treatment on a small percentage of previously infected trees. These were however successfully controlled by reapplication of fungicides at the previous rates. It may not be necessary to carry out prophylactic treatment on non-infected border trees if infected trees have been treated with fungicide. Growth rates of treated trees which had recovered returned to normal about nine months later.
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