Blister Blight on Tea Leaves
Leaf diseases are very important in tea production since the plants are grown for their young leaves. The major foliar disease of tea in Asia is blister blight. Wind-borne spores germinate on the leaf in humid conditions and the leaf is penetrated. Further growth presses out and eventually a blister is formed on the leaf. Each blister can produce up to 20 million spores. Tea prepared from blistered leaves is weak, with poor color, aroma, brightness, and briskness. Before the use of fungicides, tea losses to blister blight were staggering with 30-50% losses. Preventive copper sprays have been the mainstay of tea production for the past 60 years. Blister blight is not a problem for organic tea growers since they are permitted the use of copper sprays.
“Tea is one of the most popular beverages in the world owing to its taste, the stimulative effect, and also for its health benefits. Perennial habit of the tea plant, peculiar cultural conditions and warm humid climate of the tea growing areas are highly conducive for disease development… Among the leaf diseases, blister blight caused by Exobasidium vexans is the most important one. The disease is known to occur in almost all tea growing areas of Asia. E. vexans is an obligate parasite with no alternate host. Hence, its life cycle has to be completed on tea plant itself. The entire life cycle is completed in 11 days under conducive weather conditions or else it could extend up to 28 days… Comparisons between the crop harvested from tea fields protected by fungicide spray and those left unsprayed indicated a loss of 50% to blister blight disease in six months.”
Authors: Sowndhararajan, K., et al.
Affiliations: School of Life Sciences, India.
Title: Integrated control of blister blight disease in tea using the biocontrol agent Ochrobactrum anthropi strain BMO-111 with chemical fungicides.
Source: Journal of Applied Microbiology. 2013. 114:1491-1499.
Fungicide Experiment: Ghana (top=untreated bottom=treated)
Peanuts (or groundnuts) are widely used as a food by Africans as they are a major source of protein. The productivity of peanut in Africa is very low which is particularly attributed to foliar diseases. Disease severities are so high in Africa that at harvest 80% of the leaves on peanut plants are defoliated. Research has shown that application of fungicides can successfully control diseases of peanuts in Africa and lead to substantial increases in yield.
“Lower productivity of peanut in West Africa is attributed to biotic factors (mainly foliar diseases)…
Farmers usually attribute leaf defoliation to maturing of the crop, and yield loss from foliar diseases is not recognized. Fungicide use is not a common practice in developing countries of this region partly because of lack of resources and lack of awareness of the extent of economic and yield benefits from application of fungicide.
Data on yield benefits under on-farm studies should be quantified to bring awareness to agricultural communities, and to improve access to capital resources to demonstrate that fungicide application can be economically viable with greater returns.
The objectives of our research were to quantify yield losses due to disease and to demonstrate the influence of fungicides and SSP fertilizer application on severity of leaf spot, dry matter production and pod yield of peanut crops grown in on-station and on-farm conditions in Northern Ghana, which is representative of the important peanut producing regions of West Africa.
Applications of fungicide were effective in controlling leaf spot and improved peanut pod yield on average by 48% in the three tested village sites under on-farm conditions and by about 40% under on-station conditions at two sites.
…farmers have an interest in adopting new technologies if they are certain of economic benefits. In view of the tremendous yield advantage, fungicide recommendations are being made to peanut farmers in this region.”
Authors: Naab, J. B., et al.
Affiliation: Savanna Agricultural Research Institute
Title: Response of peanut to fungicide and phosphorus in on-station and on-farm tests in Ghana
Source: Peanut Science. 2009. 36:157-164.