EFFICACY OF SYNTHETIC AND NON-SYNTHETIC FUNGICIDES AGAINST STEM CANKER DISEASE OF TEA

Tea (Camellia sinensis) is a major source of foreign exchange in Kenya. Its production is greatly affected by the .stem canker disease (Phomopsis theae) and, thus, the need to develop effective control strategies. The efficacy of three fungicides (copper oxychloride, mancozeb and benomy 1 at concentrations of 10,25,50,100 ppm for each, and acqueous leaf extracts (10% w/v) of four indigenous plants, sage brush (Lippia javanicum), stinging nettle (Urtica massaica), savory (Satureia bi flora) and Kenya green heart (Warburgia ugandensis) were evaluated in vitro against two isolates (P 228 and P 794) of Phomopsis theae Petch, the cause of stem canker disease of tea. The variables used for the study of growth inhibition were colony diameter and number of pyenidia produced on malt extract agar, and dry weight of thallus biomass in liquid malt extract. The three fungicides differed significantly (P 0.01) from each at all concentrations. Benomyi was the most effective as it completely inhibited the two isolates of P. theae in all concentrations. Mancozeb was the next best but it was effective only at high concentrations. Copper oxychoride was found least effective even at high concentrations. Aqueous leaf extract of W. ugandensis was the most effective and completely inhibited mycelial growth, biomass accumulation and pyenidial production even at very low concentrations.