A survey of the grain chinch bug, Macchiademus diplopterus (Distant) (Hemiptera: Lygaeidae), in deciduous fruit orchards in the Western Cape, South Africa
The grain chinch bug, Macchiademus diplopterus (Distant) (Hemiptera: Lygaeidae), is a pest of export fruit from South Africa of quarantine concern. During summer adult M. diplopterus move from their host plants, usually wheat, to find shelter for aestivation, and may settle on fruit, sheltering at the stalk and calyx ends. Grain chinch bugs are endemic to the Western Cape region of South Africa, but their distribution and abundance in the fruit-growing areas of this region are not known. A survey was conducted over a period of three years (2004-2007) to determine if any particular fruit-growing area or fruit type is more prone to grain chinch bug infestation. Data on the type of vegetation surrounding the sites used in the survey, and climatic data of each area were analysed to determine which factors influence M. diplopterus abundance. No particular fruit type was found to be more prone to infestation. Areas with high numbers of M. diplopterus (Ceres, Porterville and Piketberg) had significantly lower average monthly relative humidities and minimum temperatures than areas with low numbers. Surrounding wheat fields and close proximity of wheat fields to orchards also contribute to higher numbers of grain chinch bug in the orchards. In the absence of methods to control grain chinch bug in orchards or on deciduous fruit, producers in areas with high numbers are more likely to experience problems with rejections of consignments presented for export. Research is required to develop methods to control M. diplopterus.