A survey of grain chinch bug in deciduous fruit orchards

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