Attract and surveil | Combatting invasive insects with monitoring and trapping

Hortgro Science in collaboration with the FruitFly Africa Centre of Excellence for Monitoring is conducting surveillance* and monitoring for polyphagous shot-hole borer (PSHB) and spotted wing drosophila (SWD) in the main deciduous fruit production areas of South Africa.

PSHB

Polyphagous shot-hole borer is a beetle from Asia that was first detected in Somerset West in 2019 and has subsequently been detected in traps in the Berg River, Klein Karoo, Langkloof, Stellenbosch and Wolseley regions (https://pshb.hortgro.science/monitoring/monitoring-detection-and-distribution/) – although Somerset West is the only location where infestation was detected in commercial fruit orchards.

In the current season (October 2024), PSHB was also detected in Grabouw town. Several additional traps were added to the area, and one new detection was made in January 2025 just outside of Grabouw. For PSHB monitoring, highly susceptible sentinel host trees such as English oak, London plane, boxelder, beefwood and poplar can be monitored on farms for PSHB infestation (±1mm round holes; Figure 1). Potential detections can be reported to Hortgro Science at pshb@hortgro.co.za  and more information is available at https://pshb.hortgro.science/.

Spotted wing drosophila

Spotted wing drosophila is a vinegar fly that infests most stone fruit including peaches, nectarines, plums, apricots and cherries. It also attacks blueberries, strawberries, raspberries, blackberries and other wild hosts such as bramble. Unlike other vinegar flies, SWD can cause primary damage to fruit, usually as they start to ripen. Surveillance and monitoring for SWD have been ongoing since the beginning of 2024 and SWD has now been detected in the Berg River, Ceres (Koue Bokkeveld and Warm Bokkeveld), EGVV, Hex River, Klein Karoo, Langkloof, Somerset West, Stellenbosch and Wolseley regions (Figures 3). Although the fly has been detected in several production areas, no damage to stone fruit has yet been reported. However, economic damage was seen in blueberries in December 2024.

Monitoring of SWD is done by deploying traps and conducting fruit damage assessments. Commercial traps and attractants or homemade traps baited with apple cider vinegar can be used.

• For more information on monitoring and management of SWD see the SWD Fact Sheet and Best Practice Guidelines here: https://www.hortgro-science.co.za/resources/pamphlets/
• WATCH how to make your own SWD trap or how to use commercial traps on our SWD video playlist here: https://youtube.com/playlist?list=PL8Q2I9JfqYy6zwOhFxysuZYcA8zcl7Xtz&si=o44n4VuMoSgcKD3c
• Monitoring and surveillance remain one of the most important aspects of managing invasive insects. For more information visit our website https://www.hortgro-science.co.za/  or contact Dr Minette Karsten at minettek@sun.ac.za.

 *Surveillance aims to detect invasive species as soon as they arrive in a new region to contain spread and prevent damage.