Utilizing electronic traps for early detection of Bactrocera dorsalis (Diptera: Tephritidae) in South Africa

Abstract

Bactrocera dorsalis (Diptera: Tephritidae) was declared present in the northern and north eastern areas of South Africa in 2013. The pest still has a restricted distribution in South Africa, being absent in the western and most of the south eastern parts. Monitoring for early detection of B.dorsalis in pest free areas in South Africa is routinely carried out. Conventionally, B.dorsalis populations have been monitored using ME (Methyl Eugenol) in bucket traps containing a toxicant strip (Conventional Trap). Traps are checked manually at specified intervals. Recently a McPhail type electronic trap (E-Trap) with a yellow sticky pad (to retain flies), a camera and a network device for image relay was developed to enable remote monitoring of B.dorsalis populations. The study aimed to assess the comparative efficacy of the E-trap and the conventional trap as early detection tools for B.dorsalis. The conventional trap and E-trap were compared in two locations (Schoemanskloof and Ermelo) in Mpumalanga Province, South Africa.
At Schoemanskloof 11 convetional traps and three E-traps were placed across 459 ha and at Ermelo 7 convetional traps and six E-traps were placed across 1709.69 ha. In each area, traps were at least 1 km apart. The trapping systems were monitored over 16 months (November 2022 – February 2024). Conventional traps were checked fortnightly and E-trap images were checked daily. The first incursions of B.dorsalis in 2023 was detected by the Conventional trap in Schoemanskloof (2023/01/10; average flies/trap/day = 0.1) and by the E-trap in Ermelo (2023/01/10; average flies/trap/day= 0.006). The first incursions of B.dorsalis in 2024 were detected by Conventional traps in Ermelo (2024/01/18; average flies/trap/day = 0.004) and Schoemanskloof (2024/01/24; average flies/trap/day = 0.008). This suggests that conventional traps may be more reliable for early detection, but the number of traps and trap placement may also play an important role in B.dorsalis detection