Bactrocera invadens
Picture taken by Bob Copeland

On 5 May 2010, exotic fruit fly specimens were detected in surveillance traps in the northernmost part of the Limpopo province adjacent to the Zimbabwe border. They were identified as Bactrocera invadens, a quarantine pest of serious concern to the Southern African region.

A delimiting survey was deployed by the Department of Agriculture, Forestry and Fisheries directorates Plant Health and Agricultural Product Inspection Services (APIS) on 12 May 2010 to determine the geographical extent of the occurrence. A risk assessment was conducted and phytosanitary control and containment actions were implemented with immediate effect to control the movement of fruit from the area under delimitation according to the provisions of Regulation R110 of the Agricultural Pests Act, 1983 (Act number 36 of 1983). Eradication procedures commenced on 4 June 2010 and are directed at host patches in the area between Pontdrift and Musina. Eradication will be carried out over a period of at least 8 weeks using a combination of ground applied male annihilation treatments and air/ground applied protein bait treatments.  This will be followed by another 4 week monitoring period to determine if eradication has been successful and quarantine measures can be relaxed.  Intensified monitoring will continue in the area after completion of eradication. 

Bactrocera invadens can be monitored through trapping using methyl eugenol (ME), which is an attractant specific to males of this pest; ME is commercially available and can be used with bucket type, traps e.g.Chempac Bucket trap or the Moroccan trap. Each trap should contain an ME dispenser. Extreme care must be taken while handling the attractant in order to avoid contamination on the outside of the trap.  An insecticide such as DDVP (dichlorvos) should also be placed inside each trap to kill any attracted flies. Dichlorvos is commercially available as solid strips and a small piece (1 cm x 1cm) can be used per trap. Traps should be suspended on host trees such as mango, citrus and guava. In case of vegetable crops such as tomatoes and pumpkin, which are also known hosts of B. invadens, traps can be placed in the immediate surrounding vegetation.

In order to monitor the progress of eradication, it is essential that all fruit and vegetable production areas (inclusive of home garden areas on farms) within the eradication zone have 3-5 ME baited traps per km2.

In all other fruit and vegetable production areas outside of eradication zone, surveillance trapping should either be set up or continued for detection of the pest. Density of ME baited traps for detection in production areas (inclusive of home garden areas on farms) should be 1 per km2.

When traps are set up, the following details should be recorded: farm name, location, host tree, date trap set, GPS positions). Traps should be serviced (checked and emptied of caught specimens) every week in the eradication zone and at least once every month outside of the eradication zone. Fresh attractants and dichlorvos should be placed inside the trap every 6 weeks. It is essential to record all trap servicing records (date when trap checked and date when trap re-baited) even if no specimens are caught.

All trapping information (trap details and service records) must be forwarded to the relevant surveillance co-ordinators (citrus - Aruna Manrakhan, aruna@cri.co.za, 013-7598000; deciduous fruit including grapes – Leslie Brown, leslie@dfptresearch.co.za, 021-8828470; subtropical fruits – Wilna Stones, Wilna@subtrop.co.za, 015-3073676; all other fruit and vegetable crops – Department of Agriculture, Forestry and Fisheries : Jan Hendrik Venter, JanHendrikV@nda.agric.za, 0123196384). If specimens are caught, they should be placed in closed plastic vials and the relevant surveillance co-ordinator must be contacted immediately for arrangements to forward the specimens for identification. A trapping protocol that includes datasheets for records of trap details and trap servicing is available from the surveillance co-ordinators.

Aruna Manrakhan & Vaughan Hattingh, CRI, 013-7598000; 21 June 2010