Diseases and Pests of Tea: Overview and Possibilities of Integrated Pest and Disease Management

Abstract

From the viewpoint of plant protection (phytomedicine), the demand for tea free from pesticide residues is in conflict with the demand for high quality from the consumer, and with the demand for high yield and low labour input, from the producer. High yield in tea has been mainly achieved by the elimination of tree shade, and reduction of losses due to diseases and pests with pesticides. Elimination of shade changed the agro-environment, with increased growth of weeds, higher input of fertilizers, and with increased susceptibility to certain diseases (stem canker due to sun-scorch, grey blight) and pests (mites). However, shade also can be detrimental to yield with unsuitable tree species, or too much shade in the rainy season which encourages the incidence of blister blight (Exobasidium vexans) and some insect pests (tea mosquito bug). Economic loss of tea due to diseases is higher compared to animal pests (pests), the blister blight being the main disease. Pressure of diseases and pests on tea depends also on the control strategy and the climatic environment. Reducing pesticides may be feasible by reducing the threat of diseases and/or pests through cultivation in less disease and pest prone environments (altitude, shade), in choosing disease or pest tolerant clonal tea-varieties, by choosing pesticides with low interference on natural enemies of pests and diseases, and by applying pesticides according to economic threshold. The long standing time of the tea bushes favours slow developing root diseases. These are reviewed and the integrated control is discussed in detail with eradication, with pesticides, and with improvement of soil microflora. Leaf and stem diseases are reviewed. Integrated pest and disease management of blister blight and the scarlet tea mite (Brevipalpus phoenicis), are discussed in detail.