Microbial & Agricultural Ecology Laboratory, Department of Ecology, Assam University, PB No- 63, Sllchar- 788 001, Assam, India

Background and objectives
Until recently copper fungicide was the only fungicide to control the leaf and stem diseases of the tea, but results were always variable. Recently some systemic fungicides including some ergosterol biosynthesis inhibitors (EBIs) were found to be more effective and economic in controlling blister blight diseases than standard copper fungicide. A disease-forecasting system can possibly play an important role in minimising the use of chemicals by suggesting the correct timing of sprays. Against this perspective, the present investigations on the aerobiological survey, bio-efficiencies of systemic fungicides and bio-agents against some leaf diseases (blister blight, black rot and red spot disease) and stem (red rust )diseases were carried out.

Results and conclusions
An aerobiological survey on the incidence of blister blight (Exobasidium verans) disease in tea shows three peaks in spore accumulation (July, Sept., Oct.). A forecast can be made on the incidence of the disease on the basis of these results. Prophylactic application of systemic fungicide (hexaconazole, tridemorph) in June and August would reduce the inoculum potential on the leaf surface affecting the disease severity. Systemic fungicides gave excellent control of Blister blight, Black rot, Red rust, and Red spot diseases. Hexaconazole, propiconazole and tridemorph controlled blister blight more efficiently along with substantial increase in yield. Black rot, Red rust, and Red spot diseases have also been controlled more efficiently with tridemorph and carbendazim, respectively. The systemic fungicides have better potential to control the disease compared to the traditional protectant fungicides and hence should be preferred. The results suggest that the bio-agents may also play an important role in the integrated approach to control some of the tea diseases (i.e. Black rot).

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2. Dutta B K 1994. Proceedings of the 32nd Tocklai Conference (1994), pp 247-56.