Phytosanitary control of grain chinch bug in packed fruit cartons

The grain chinch bug (GCB) Macchiademus diplopterus is endemic to the Western Cape and as such is classified as a quarantine pest.  The aim of this project was to evaluate post-harvest methods of control to ensure that packed fruit cartons are free of live GCB adults and acceptable to international quarantine standards.  Cold storage trials were carried out at a commercial cold store in Ceres.  GCB adults were subjected to controlled atmosphere conditions (treatment) and regular atmosphere conditions (control) for a period of 6 weeks during 2001 and 10 weeks during 2002.  In addition, two packhouses were monitored in the Ceres area and low pressure air-suction was assessed as a possible control option after harvest.

It was found that packhouses situated near fruit orchards or open fields appear to be more at risk from GCB infestations than those surrounded by buildings, although it could not be determined to what extent infestations around packhouses contribute to infestations of fruit being packed.  Low pressure air suction was not successful on the number of pears that were found to be infested from the sample collected for this purpose.  The results showed that GCB appear to be very cold-adapted and that at least nine weeks will be required to achieve 100% mortality under controlled atmosphere conditions.  A mortality of 100% was never achieved under regular atmosphere conditions.  Sufficient data was generated within this project to conclude that low temperature in itself is not sufficient to effectively sterilize pears from GCB infestations and that the time required to achieve 100% mortality under controlled atmosphere conditions would probably compromise fruit quality or be unacceptably long.