The division conducts research on tea diseases, biological control, biofertilizers and microbiology.

TEA DISEASES
BLISTER BLIGHT Caused by the fungus Exobasidium vexans is the major disease affecting the tender harvestable shoots of tea resulting in enormous crop loss. The division has screened a number of new generation fungicides for their field efficacy against blister blight. Hexaconazole, bitertanol, propiconazole and tebuconazole are the most effective systemic fungicides recommended against this disease. A combination schedule of triazole fungicides (hexaconazole, propiconazole) and morpholine fungicide (tridemorph) has been recommended recently. Apart from chemical control, experiments on biological control measures are in progress. Based on extensive epidemiological and aerobiological studies on the pathogen the division has developed a forecasting model. With the help of this model, disease incidence can be predicted well in advance and based on the prediction the control measures can be planned which will result in considerable savings in the management of the disease.

GREY BLIGHT AND DIE BACK OF SHOOTS This disease is caused by Pestalotia theae / Pestalotiopsis theae. Mature leaves, young shoots and bare stalks are affected by this pathogen. Infection on young shoot results in die back of shoots. Die back of shoots became a major problem mainly due to continuous shear harvesting. Grey blight adversely affects the health of the bushes, which in turn affects yield while die back of young shoots directly leads to substantial crop loss. Studies indicated that the disease incidence is in its peak during July to December. The crop loss due to the disease is 17%. The economic threshold level of the disease is fixed as 18% at a sale price of Rs.50/- per kg of made tea. Spraying of carbendazim, mancozeb, or thiophanate methyl is suggested to control the disease.


COLLAR CANKER A wound pathogen, Phomopsis theae is responsible for the disease. It is prevalent in young tea and clones are more susceptible than seedlings. In vitro studies indicated that the pathogen completes its life cycle in 10-13 days. Impact of predisposing factors on disease development indicated that the nature of soil is an important factor. Disease incidence was more in gravelly soil. Deep planting, application of fertilizer near to plant collar and mulching with raw coir pith close to the collar predispose the disease. Soil drenching of the systemic fungicide carbendazim and application of the same as wound dressing provided satisfactory control. However, the efficacy was superior when biological control agents like Trichoderma harzianum and Gliocladium virens, were applied both to the soil arrow the bush and used for wound dressing.