White Stem Borer (WSB) in Western Ghats and shifts towards Robusta coffee: Evidences from a recent household survey of Arabica coffee growers in Kodagu district of Karnataka state

摘要

The coffee growing regions in the Western Ghats are witnessing a major shift from Arabica to Robusta cultivation over the past few years. This paper analyses the major causes for the shift by using a newly collected sample survey data of 60 Arabica coffee growers in Kodagu district. Among the interviewed growers, about 68.33 per cent of growers were shifting towards Robusta, while about 21.67 per cent of growers were willing to shift, but unable to shift towards Robusta. However about 10 per cent ofgrowers were not willing to shift towards Robusta, despite several constraints. Among the growers shifting towards Robusta, about 90 per cent of them opinioned that White Stem Borer (WSB) was the major cause for the shift. Henceforth, this paper focuseson White Stem Borer (WSB), currently a major pest in Indian Arabica.Though the occurrences of WSB are universal in all Arabica growing regions, the incidence varied across the estates.while the severity of incidence was found to be increasing over the years.The Mean average annual reduction in yield due to WSB was about 20 per cent, while the average uprooting of plants being 60 plants per acre in individual estates.Further on.the major factors responsible for WSB attack were analyzed. Among the environmental factors, about 47 per cent of growers opinioned the rise in temperature as a major cause for WSB attack, while about 35 per cent growers' opinioned erratic rainfall followed by lower elevation (18 per cent)as the major factors responsible for WSBattack. It was interesting to note that the incidence of White Stem Borer(WSB) was severe in estates located at Lower Elevation (LE) and Low Rainfall (LR) regions.About 20 per cent of the estates lying in these regions experienced very high incidence ofborer attack, wherein the uprooting of plants varied between 50-100 plants per acre. However, the incidence of borer attack was found to be low in estates located High Elevation (HE) and Medium Rainfall (MR) regions. Among the management conditions, about 30 per cent of growers opinioned the maximum spreads of WSBwere through the neglected neighboring estates and improper management of shades (24 per cent) and Ineffective Control Measures (24 per cent). The control of WSB included both cultural and chemical controls.The cultural costs increased with the incidenceof attack, ranging between Rs.268 to Rs.3000 per acre. The average chemical costs for WSB control were estimated to be Rs.6930 per hectare.The study has suggested that inter-countries combined and co-ordinated research for WSB control, combination of antixenosis and antibiosis characters in coffee, biological insecticides could also prove effective. Besides, proper training for cultural control would turn effective.The overall results show that currentlyWSB had a very strong impact on Arabica productivity, resulting in net reduction in growers' income who are thereby shifting towards lower cost Robusta cultivation. At a macro level, this shift could handicap the country's overall Arabica production.